Ammonia is emerging as a viable alternative to fossil fuels in combustion systems, aiding in the reduction of carbon emissions. However, its use faces challenges, including NOx emissions and low flame speed. Innovative approaches and technologies have significantly advanced the development and implementation of ammonia as a zero-carbon fuel. This review explores current advancements in using ammonia as a fuel substitute, highlighting the complexities that various systems need to overcome before reaching full commercial maturity in support of practical decarbonising global strategies. Different from other reviews, this article incorporates insights of various industrial partners currently working towards green ammonia technologies. The work further addresses fundamental complexities of ammonia combustion, crucial for its practical and industrial implementation in various types of equipment.

In order to limit global warming to 2 °C, countries have adopted carbon capture and storage (CCS) technologies to reduce greenhouse gas emission. However, it is currently facing challenges such as controversial investment costs, unclear policies, and reduction of new energy power generation costs. In particular, some CCS projects are at a standstill. To promote the development of CCS projects in different countries, this paper reviews and compares energy conservation and emission reduction policies and different national goals. From a policy perspective, CCS-driven policies are analyzed. Based on this, corresponding policy recommendations are put forward, in order to promote the healthy development of global CCS technology and deal with climate issues more effectively. With less than 10 years away from the short-term goal, promoting the development and application of CCS projects requires scientific research from universities, enterprises and governments in order to attain zero or negative CO₂ emission. On the basis of focusing on the development of CCS technology, according to the actual situation of each country, the appropriate application of CCS engineering should focus on the development of science and technology, rather than a unified requirement around the world.

Decarbonization of the energy system is the key to China’s goal of achieving carbon neutrality by 2060. However, the potential of wind and photovoltaic (PV) to power China remains unclear, hindering the holistic layout of the renewable energy development plan. Here, we used the wind and PV power generation potential assessment system based on the Geographic Information Systems (GIS) method to investigate the wind and PV power generation potential in China. Firstly, the high spatial-temporal resolution climate data and the mainstream wind turbines and PV modules, were used to assess the theoretical wind and PV power generation. Then, the technical, policy and economic (i.e., theoretical power generation) constraints for wind and PV energy development were comprehensively considered to evaluate the wind and solar PV power generation potential of China in 2020. The results showed that, under the current technological level, the wind and PV installed capacity potential of China is about 56.55 billion kW, which is approximately 9 times of those required under the carbon neutral scenario. The wind and PV power generation potential of China is about 95.84 PWh, which is approximately 13 times the electricity demand of China in 2020. The rich areas of wind power generation are mainly distributed in the western, northern, and coastal provinces of China. While the rich areas of PV power generation are mainly distributed in western and northern China. Besides, the degree of tapping wind and PV potential in China is not high, and the installed capacity of most provinces in China accounted for no more than 1% of the capacity potential, especially in the wind and PV potential-rich areas.

Solar energy is the most sustainable alternative to fossil fuels. The production of solar thermochemical fuels from water/carbon dioxide not only overcomes the intermittent nature of solar energy, but also allows for flexible transportation and distribution. In this paper, the challenges for solar thermochemical H₂/CO production are reviewed. New perspectives and insights to overcome these challenges are presented. For two-step cycles, the main challenges are high temperatures, low conversions and the intensive oxygen removal work. Theoretically feasible temperature and pressure ranges are needed to develop reactant materials. The fundamental mechanism to reduce the temperature and the potential to improve the efficiency by minimizing the oxygen removal work need be revealed. Various material modification strategies and advanced reactors are proposed to improve the efficiency by reducing the temperature and enhancing heat transfer process. But the oxygen removal work required has not been minimized. For multi-step cycles, the main challenges are the separation of corrosive acid and insufficient reaction kinetics. For the separation of acids, many methods have been proposed. But these methods require extra energy and causes undesired side reactions or byproducts. The reaction kinetics have been enhanced by improving catalysts with noble materials or complex fabrication methods. Developing novel multi-step cycles using metal oxides, hydroxides and carbonates may be promising.

Multi-stage reverse electrodialysis (MSRED) offers a promising way for efficient salinity gradient energy harvesting. Here, an improved model of the MSRED system under serial control strategy is proposed. The technical-economic analysis is conducted with considering discount, depreciation and different regional tax and electricity price levels under the maximum net power output conditions. Results reveal that net power output and energy efficiency both increase first with increasing stage numbers, reach their maximum values, and then decrease. For 5 M/0.05 M solutions, the optimal net power output of 4.98 kW is obtained at the stage number n = 12. The optimal stage number corresponding to the maximum net power increases with increasing feed solution concentrations. Due to the compromise between net power generation and capital cost, there exist optimal stage numbers leading to the lowest LCOE and largest NPV, respectively. Higher feed solution concentration can significantly decrease the system LCOE and increase the NPV. The optimal stage number corresponding to the maximum NPV increases with increasing feed solution concentrations. In Germany, for 5 M/0.05 M solutions, the lowest LCOE of 0.061 €·kWh⁻¹ is achieved at n = 3 while the highest NPV over the system lifecycle of 52,005 € is obtained at n = 8. Lower tax, higher electricity price, appropriate membrane price and stage numbers, and high salinity gradient sources can significantly accelerate the commercial completeness of the MSRED systems.

From a macro-energy system perspective, an energy storage is valuable if it contributes to meeting system objectives, including increasing economic value, reliability and sustainability. In most energy systems models, reliability and sustainability are forced by constraints, and if energy demand is exogenous, this leaves cost as the main metric for economic value. Traditional ways to improve storage technologies are to reduce their costs; however, the cheapest energy storage is not always the most valuable in energy systems. Modern techno-economical evaluation methods try to address the cost and value situation but do not judge the competitiveness of multiple technologies simultaneously. This paper introduces the ‘market potential method’ as a new complementary valuation method guiding innovation of multiple energy storage. The market potential method derives the value of technologies by examining common deployment signals from energy system model outputs in a structured way. We apply and compare this method to cost evaluation approaches in a renewables-based European power system model, covering diverse energy storage technologies. We find that characteristics of high-cost hydrogen storage can be more valuable than low-cost hydrogen storage. Additionally, we show that modifying the freedom of storage sizing and component interactions can make the energy system 10% cheaper and impact the value of technologies. The results suggest looking beyond the pure cost reduction paradigm and focus on developing technologies with suitable value approaches that can lead to cheaper electricity systems in future.

Sodium ion batteries (SIBs) have attracted great interest as candidates in stationary energy storage systems relying on low cost, high abundance and outstanding electrochemical properties. The foremost challenge in advanced NIBs lies in developing high-performance and low-cost electrode materials. To accelerate the commercialization of sodium ion batteries, various types of materials are being developed to meet the increasing energy demand. O3-type layered oxide cathode materials show great potential for commercial applications due to their high reversible capacity, moderate operating voltage and easy synthesis, while allowing direct matching of the negative electrode to assemble a full battery. Here, representative progress for Ni/Fe/Mn based O3-type cathode materials have been summarized, and existing problems, challenges and solutions are presented. In addition, the effects of irreversible phase transitions, air stability, structural distortion and ion migration on electrochemical performance are systematically discussed. We hope to provide new design ideas or solutions to advance the commercialization of sodium ion batteries.

Distributed energy system, a decentralized low-carbon energy system arranged at the customer side, is characterized by multi-energy complementarity, multi-energy flow synergy, multi-process coupling, and multi-temporal scales (n-M characteristics). This review provides a systematic and comprehensive summary and presents the current research on distributed energy systems in three dimensions: system planning and evaluation, modeling and optimization, and operation and control. Under the regional environmental, resource, and policy constraints, planning distributed energy systems should fully integrate technical, economic, environmental, and social factors and consider device characteristics, system architecture, and source-load uncertainties. Further, this review presents four modeling perspectives for optimizing and analyzing distributed energy systems, including energy hub, thermodynamics, heat current, and data-driven. The system’s optimal operation and scheduling strategies, disturbance analysis, and related control methods are also discussed from the power system and thermal system, respectively. In all, more research is required for distributed energy systems based on an integrated energy perspective in optimal system structure, hybrid modeling approaches, data-driven system state estimation, cross-system disturbance spread, and multi-subject interaction control.

This study revisits the question of “whether firms are doing well by doing good?”. We examine shareholders-sponsored corporate socially responsible (CSR) proposals related to Environmental, Social, and Governance (ESG) that are voted to pass or fail by a small margin. The adoption of those “close call” proposals is regarded as equivalent to a random assignment of CSR policies and, therefore, provides a quasi-experimental setting to capture the causal influence of CSR on firm performance. We apply the regression discontinuity design (RDD) and find that CSR proposals’ passage leads to a significant positive abnormal return on the voting day. The results are robust with both parametric and nonparametric approaches of RDD and different polynomial orders. However, we fail to identify a significant change in financial performance in the long-term. One possible reason is that passing a CSR proposal could be symbolic, rather than substantial.

This review reports the most recent developments of thermoelectric (TE) system coupled with phase change material (PCM) and its promising integration options within various PCM deployment and structure design. These innovative TE coupled with PCM (TE-PCM) systems provide heat/cold energy with additional electric power which implies better harnessing of multiform energy. Fundamentals of TE-PCM system including thermoelectric effect are presented along with a basic mathematical formulation of the physical problem. The classification principles and configuration types of such systems are also summarized. The most representative studies related to the utilization of TE-PCM system in diversified application scenarios and their compatibility with other energy systems have been comprehensively reviewed and analyzed, including the component and structure optimization. In-depth analysis of the main technical and operational challenges in the future has been carried out, and the prospective development of more efficient TE-PCM system and its hybrid configurations are projected based on the current technological level.

Heating decarbonization is a major challenge for China to meet its 2060 carbon neutral commitment, yet most existing studies on China’s carbon neutrality focus on supply side (e.g., grid decarbonization, zero-carbon fuel) rather than demand side (e.g., heating and cooling in buildings and industry). In terms of end use energy consumption, heating and cooling accounts for 50% of the total energy consumption, and heat pumps would be an effective driver for heating decarbonization along with the decarbonization on power generation side. Previous study has discussed the underestimated role of the heat pump in achieving China’s goal of carbon neutrality by 2060. In this paper, various investigation and assessments on heat pumps from research to applications are presented. The maximum decarbonization potential from heat pump in a carbon neutral China future could reach around 1532Mton and 670Mton for buildings and industrial heating respectively, which show nearly 2 billion tons CO₂ emission reduction, 20% current CO₂ emission in China. Moreover, a region-specific technology roadmap for heat pump development in China is suggested. With collaborated efforts from government incentive, technology R&D, and market regulation, heat pump could play a significant role in China’s 2060 carbon neutrality.

Carbon capture, utilization, and storage (CCUS), as a technology with large-scale emission reduction potential, has been widely developed all over the world. In China, CCUS development achieved fruitful outcomes. CCUS gained further broad attention from the announcement of the carbon neutrality target by 2060, as CCUS is an indispensable important technology to realize carbon neutrality. It helps not only to build zero-emission and more resilient energy and industry systems but also provides negative emission potential. This paper discusses the new demand for carbon capture, utilization, and storage development brought by the carbon neutrality target analyzes the development status. As there remain various challenges of CCUS development, this paper focuses on several key issues for CCUS development in China targeting carbon neutrality: 1) how to reposition the role of CCUS under the carbon neutral target? 2) how shall we understand the technology development status and the costs? 3) what role shall utilization and storage play in future? 4) potential strategy applied to solve challenges of source-sink mismatch and resources constraints; and 5) new business model that suits large scale deployment of CCUS. This paper puts forward several policy suggestions that should be focused on now in China, especially to raise awareness under the vision of carbon neutrality that the role and contribution of CCUS are different, to accelerate the establishment of a comprehensive and systematic enabling environment for CCUS.

Solar hydrogen production through water splitting is the most important and promising approach to obtaining green hydrogen energy. Although this technology developed rapidly in the last two decades, it is still a long way from true commercialization. In particular, the efficiency and scalability of solar hydrogen production have attracted extensive attention in the field of basic research. Currently, the three most studied routes for solar hydrogen production include photocatalytic (PC), photoelectrochemical (PEC), and photovoltaic-electrochemical (PV-EC) water splitting. In this review, we briefly introduce the motivation of developing green hydrogen energy, and then summarize the influential breakthroughs on efficiency and scalability for solar hydrogen production, especially those cases that are instructive to practical applications. Finally, we analyze the challenges facing the industrialization of hydrogen production from solar water splitting and provide insights for accelerating the transition from basic research to practical applications. Overall, this review can provide a meaningful reference for addressing the issues of efficiency improvement and scale expansion of solar hydrogen production, thereby promoting the innovation and growth of renewable hydrogen energy industry.

CO₂ capture is a process with a high energy consumption, and its large-scale implementation should be based on comprehensive analysis of its impact on the energy, economy, and environment. The process of injecting CO₂ into existing oil fields is a well-known enhanced oil recovery (CO₂-EOR) technique. Using CO₂ as a working fluid to recover oil can compensate for the energy consumption of the capture and transport processes, increasing the feasibility of CO₂ capture while achieving carbon sequestration. In this study, a full-chain CO₂ capture, utilization, and storage (CCUS) system based on the post-combustion capture method is deconstructed and coupled. A full-chain energy consumption calculation software is developed, and optimization analysis of the energy consumption system is conducted. The energy budget of the oil displacement utilization is deconstructed, and the advantages of the water alternating gas (WAG) method are clarified from an energy budget point of view. The analysis reveals that the benefits of CO₂-EOR are far greater than the energy consumption of other CCUS processes, and CCUS-EOR is a CO₂ utilization method with positive energy benefits. Based on the simulation of the effects of N₂ and CH₄ on the recovery factor, a multi-well combined injection-production method is proposed, and the reasons for increasing profit are analyzed.

Hydrogen, as a clean energy carrier, is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies, has ignited much attention in the past decades based on the high current density, greater energy efficiency, small mass-volume characteristic, easy handling and maintenance. To date, substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review, we firstly compare the alkaline water electrolysis (AWE), solid oxide electrolysis (SOE), and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore, we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly, current collector, and bipolar plate). Finally, the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.

In recent years, with the increasing attention paid to climate risks, the changes in climate policies are also more full of uncertainties, which have brought tremendous impact to economic entities, including companies. Using the dynamic threshold model, this study investigates the nonlinear and the asymmetric effect of climate policy uncertainty on Chinese firm investment decisions with panel data of 128 Chinese energy-related companies from 2007 to 2019. The empirical findings indicate that the influence of climate policy uncertainty on firm investment is significantly nonlinear. Overall, climate policy uncertainty is not apparently related to corporate investments in the high-level range, while it negatively affects the investments in the low-level range. In addition, to be more specific, the negative impact of climate policy uncertainty on the mining industry is tremendous, while the influence on the production and supply of electricity, heat, gas, and water sector is remarkably positive. The results of this study could help the company managers and policymakers to arrange appropriate related strategies under different climate policy conditions.

Coal consumption leads to over 15 billion tons of global CO₂ emissions annually, which will continue at a considerable intensity in the foreseeable future. To remove the huge amount of CO₂, a practically feasible way of direct carbon mitigation, instead of capturing that from dilute tail gases, should be developed; as intended, we developed two innovative supporting technologies, of which the status, strengths, applications, and perspective are discussed in this paper. One is supercritical water gasification-based coal/biomass utilization technology, which orderly converts chemical energy of coal and low-grade heat into hydrogen energy, and can achieve poly-generation of steam, heat, hydrogen, power, pure CO₂, and minerals. The other one is the renewables-powered CO₂ reduction techniques, which uses CO₂ as the resource for carbon-based fuel production. When combining the above two technical loops, one can achieve a full resource utilization and zero CO₂ emission, making it a practically feasible way for China and global countries to achieve carbon neutrality while creating substantial domestic benefits of economic growth, competitiveness, well-beings, and new industries.

Achieving carbon neutrality by 2060 is an ambitious goal to promote the green transition of economy and society in China. Highly relying on coal and contributing nearly half of CO₂ emission, power industry is the key area for reaching carbon-neutral goal. On basis of carbon balance, a criterial equation of carbon neutral for power system is provided. By means of the equation, the different effects of three technical approaches to achieve carbon neutrality, including energy efficiency improvement, shifting energy structure and CO₂ capture, utilization and storage (CCUS) technology, had been evaluated. The results indicate that building a carbon-neutral power system requires comprehensive coordination between energy efficiency, renewable energy and CCUS technology. In particular, the unique role of CCUS in achieving carbon neutral target was investigated. For any power systems with fossil energy input, CCUS and negative emission technologies is indispensable to reach carbon neutrality. However, rather high energy consumption and costs is the critical gas deterring the large scale deployment of CCUS. Considering the specific conditions of China’s power industry, before the time window between 2030 and 2040 being closed, CCUS would either be ready for large scale deployment by reducing energy consumption and costs, or be phased out along with the most coal power plants. Conclusively, carbon neutral scenario will give CCUS the last chance to decarbonize the fossil fuel, which has great significance for China.

The Paris Agreement, a landmark in the multilateral process of global climate governance, not only demonstrates the greatest inclusiveness and feasibility based on science and principles, but also points out the general direction of the global green and low-carbon transition. The Agreement has set a global goal to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels, and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius by the end of the century. To achieve this long-term objective, developed countries should take the lead in reducing emissions as soon as possible, which is fundamental to the achievement of net-zero global emissions at an early date. China’s goal of striving to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060 shows its great ambition, strength, and responsibility as a major country, indicating that China is committed to realizing carbon neutrality from carbon peaking in the shortest time in global history, and will make greater efforts and contributions to achieve the goals set out in the Paris Agreement.

With the global ambition of moving towards carbon neutrality, this sets to increase significantly with most of the energy sources from renewables. As a result, cost-effective and resource efficient energy conversion and storage will have a great role to play in energy decarbonization. This review focuses on the most recent developments of one of the most promising energy conversion and storage technologies - the calcium-looping. It includes the basics and barriers of calcium-looping beyond CO₂ capture and storage (CCS) and technological solutions to address the associated challenges from material to system. Specifically, this paper discusses the flexibility of calcium-looping in the context of CO₂ capture, combined with the use of H₂-rich fuel gas conversion and thermochemical heat storage. To take advantage of calcium-looping based energy integrated utilization of CCS (EIUCCS) in carbon neutral power generation, multiple-scale process innovations will be required, starting from the material level and extending to the system level.

Due to the large amount of greenhouse gas (GHG) emissions and the high dependence on fossil energy, the aviation industry has attracted a lot of attention for emission reduction and sustainable development. Biomass is a green and sustainable renewable resource, and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction. In this study, the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways, including biomass aqueous phase reforming (APR), hydrogenated esters and fatty acids (HEFA), and hydrothermal liquefaction (HTL). Compared with fossil jet fuels, the three bio-jet fuels have a great advantage on global warming potential (GWP), contributing 29.2, 43.6 and 51.2 g CO₂-eq/MJ respectively. In general, as a relatively new bio-jet fuel conversion technology, the technology of aqueous phase reforming has minimal environmental impact. If the barriers of raw material availability and economy could be broken down, bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.

This paper provides an overview of financial economics-based research on carbon risk with an emphasis on corporate finance. In the corporate finance literature, carbon risk refers to the impact of society’s transition to a low-carbon economy on firm value due to tightening regulations, changing consumer preferences, reputational damage, etc. We focus on the links between carbon risk and different firm performance factors, such as firm risk, cost of capital, financial performance, firm value, and corporate decisions. Although research on carbon risk is still emerging in the corporate finance field, the amount of literature on this topic has been increasing, especially in the last 2 years. We find that some results are robust, while others are mixed. This indicates that conflicting hypotheses still exist, leading to a need for more in-depth exploration.

Striving to peak carbon emissions and achieve carbon neutrality (known as the "Dual-Carbon" goal) is an inevitable requirement for elevating the environmental resource constraints and realizing harmonious coexistence between the mankind and the earth. In the energy system, nuclear energy offers various advantages, such as high energy density, low carbon emission, strong environmental adaptability and large potential for energy co-generation and co-supply. It is one of the supporting energy sources for the transformation and upgradation of the energy system to a clean, efficient and low-carbon way. In this paper, the opportunities and challenges for innovation-driven nuclear energy development in the fields of electricity generation, hydrogen production, heat supply and seawater desalination under the goal of "Dual-Carbon" are discussed and analyzed. Besides, the relevant research on improving the safety and economy of the pressurized water reactor (PWR) and sodium-cooled fast reactor (SFR) conducted by the Nuclear THermal-hydraulic research Lab (NuTHeL) of Xi’an Jiaotong University is briefly introduced.

Ammonia has been considered as a novel fuel for decarbonization purposes. However, emissions from combustion systems are still posing a problem. Therefore, experimental and numerical simulations have been conducted to study the concentration of exhaust emissions (Nitric oxide “NO”, Nitrous oxide “N₂O”) from burning the ammonia/hydrogen (NH₃/H₂) blend 85/15 (vol%). The effects were measured at various thermal powers ranging 10 to 20 kW and with different Reynolds numbers from 20,000—40,000. The experimental points were numerically investigated in the Ansys CHEMKIN-Pro environment employing seven chemical kinetic mechanisms taken from the literature. All experiments have been undertaken at standard atmospheric conditions. The experimental results showed that both NO and N₂O gradually increased when the Reynolds number increased from 20,000 to 40,000. Along with that, the concentration of NO emissions at the exhaust reported minimum level when the Re = 20,000 due to lower reactivity radical formation, all that led to a deterioration of the flame characteristics. Also, the integrated radical intensities of NO*, OH*, NH*, and NH₂* demonstrate an increasing trend as Re increased from 20,000 to 40,000. In terms of thermal power, N₂O suffered an abrupt decrease when the thermal power increased up to 15 kW, while the opposite occurs for NO. In addition, the radicals intensity of OH*, NH*and NH₂* figures show an increase in their concentration when the thermal power increased up to 15 kW then decreased with increasing thermal intensity to reach 20 kW, reflecting into increased NO productions and decreased N₂O levels. The numerical analysis showed that Stagni, Bertolino, and Bowen Mei were the most accurate mechanisms as these give a good prediction for NO and N₂O. The study also showed that the chemical reaction (HNO + O₂ ↔ NO + HO₂) is the main source of NO formation. While the chemical reaction (NH + NO ↔ N₂O + H) is responsible for the formation of N₂O by consuming NO and when there will be abundance in NH radicals. Finally, dealing with a blended fuel of high ammonia concentration encourages ammonia chemistry to become more dominant in the flame. It decreases the flame temperature, hence lowering heat loss between the flame and the surrounding.

At present, insufficient works have provided insights into the application of adsorption to remove CO₂ in flue gas below room temperatures under ambient pressure. In this work, the effects of temperature, CO₂ partial pressure and moisture on dynamic adsorption characteristics for CO₂ are conducted for various adsorbents. Based on our findings, lower the adsorbing temperature can drastically enhance the adsorption of carbon dioxide over molecular sieves and activated carbon. Among various adsorbents, 13X molecular sieve shows highest adsorption capacity. With a concentration of 10% CO₂ in flue gas, the specific adsorption capacity of CO₂ over 13X molecular sieve is 0.11, 2.54 and 5.38 mmol/g at 80 °C, 0 °C and − 80 °C, respectively. In addition, the partial pressure of CO₂ also has a significant impact on the adsorption capacity. With the increment of the concentration of CO₂ from 1% to 10% under 0 °C, the specific capacity of 13X molecular sieve increases from 1.212 mmol/g to 2.538 mmol/g. Water vapor in flue gas can not only reduce the specific adsorption capacity of CO₂ due to competing adsorption, but also increase the heat penalty of molecular sieve regeneration due to the water adsorption. An overall analysis is conducted on the energy penalty of capture 1 ton CO₂ at various adsorption temperatures between − 80 °C and 80 °C, considering both the heat penalty of molecular sieve regeneration as well as the energy penalty for cooling the adsorber. It is found that the lowest energy penalty is about 2.01 GJ/ton CO₂ when the adsorption is conducted at 0 °C.

Ammonia serves as an irreplaceable raw material for nitrogen fertilizers, which is essential for global food production. In addition, it has been recently endowed with a new function as a carrier of renewable energy, demonstrating significant research prospects. However, the highly developed ammonia industry results in abundant nitrogenous wastes in nature, thus causing severe nitrogen pollution and disrupting the global nitrogen cycle. The environmentally friendly electrocatalytic technologies for upcycling nitrogenous wastes to green ammonia represent a highly valuable transformation strategy. In this review, we present three effective pathways for the electrocatalytic reduction of nitrogenous wastes to green ammonia, including nitrate reduction reaction (NO₃RR), nitrite reduction reaction (NO₂RR), and nitric oxide reduction reaction (NORR). Furthermore, achievements and challenges associated with electrocatalysts for green ammonia synthesis are discussed in terms of noble metal-based electrocatalysts, non-noble metal-based electrocatalysts, and metal-free electrocatalysts. Moreover, this review provides a systematic perspective on reaction mechanisms, catalyst design, and future developments, offering new insights and prospects for the value-upgrading cycle of nitrogenous substances. By exploring the potential of green ammonia synthesis, we aim to contribute to the development of sustainable and environmentally friendly ammonia production.

Reducing carbon emissions in the buildings sector is of great significance to the realization of China’s carbon peak and neutrality goals. By analyzing factors influencing buildings carbon emissions at the operational stage, this paper applies the China Building Carbon Emission Model (CBCEM) to make medium and long-term forecasts of China’s building operation carbon emissions, discussing the goals and realization paths of China’s dual carbon goals in the buildings sector. The results show that building operation carbon emissions, according to the current development model in the buildings sector, will peak in 2038-2040 with a peak carbon emission of about 3.15 billion tons of CO₂; however, by 2060, carbon emissions will still be 2.72 billion tons of CO₂, falling short of China’s dual carbon goals. The carbon saving effects of three scenarios, namely clean grid priority, building photovoltaic priority and energy efficiency enhancement priority, were measured and shown to be significant in all three scenarios, but the building photovoltaic priority and energy efficiency enhancement priority scenarios were superior in comparison.

A new technical route of organic matter capture and carbon fixation is proposed in response of the increasingly strict emission standards of volatile organic compounds (VOCs) in petrochemical industry and the Chinese national strategic development goals of carbon peak and carbon neutralization. A closed loop from raw materials to adsorbents for gas treatment can be achieved by two key technical characteristics: (1) construct a new mesoporous adsorbent with complete desorption and regeneration function by carbon nanotubes (CNTs); (2) convert gaseous organic matter which cannot be recycled in liquid/gas state to CNTs. It realizes the resource integration of "turning waste into treasure" and maximizes the carbon emission reduction effect of waste gas treatment process without consuming extra precious fossil fuel, compared with the traditional technologies of VOCs treatments, including combustion or catalytic oxidation. What’s more, the increase in supply of various green electricity is expected to change the current situation of large investment and heavy cost burden of environmental protection technology, and make a great contribution to the national carbon peak and carbon neutrality policy.

The building sector is one of the three major energy consumption areas and one of the main areas responsible for carbon emissions. In 2019, carbon emissions related to construction and building operations in China accounted for 38% of the total social carbon emissions, of which construction accounted for 16% and operations accounted for 22%. Due to its large volume and high energy consumption per unit area, public buildings account for 38% of the operating energy consumption of all buildings, that is, 8% of the total national energy consumption. At this time, the building industry must take decarbonization actions to avoid a delay in realizing carbon neutrality and an emission peak. We need to form a unified process for the implementation boundary, implementation path, and index system to build a zero-carbon implementation plan for China’s public building sector. Based on bottom-up practical cases, this paper proposes the KAYA model, which is applicable to different scales and different types of public buildings/communities, and proposes specific and feasible plans. Through the implementation of demand reduction, energy efficiency improvement, and the fully-use of renewable energy in all five clear steps, this paper promotes the implementation of decarbonization in China’s building industry.

Climate change is an ever-present issue, which has a vast variety of potential solutions, one of which being carbon capture. This paper aims to use bibliometric analysis techniques to find trends in carbon capture within the technologies of adsorption, absorption, membranes, and hybrid technologies. The Web of Science core collection database performed bibliometric searches, with the ‘Bibliometrix’ plug-in for R software, performing the bibliometric analysis. Bibliometric data spanned across 1997-2020 and the investigation found that adsorption technologies dominated this period in terms of citations and articles, with hybrid technologies being the least produced but rising in scientific productivity and citations. The Analysis found China and the United States of America to be the dominant producers of articles, with global collaboration being central to carbon capture. The ‘International Journal of Greenhouse Gas Control’ ranked as the top producer of articles however, the ‘ACS Applied Materials & Interfaces’ was the leading journal in terms of H-index.

The Loess Critical Zone (LCZ) is located in the intersection of bedrock, groundwater, pedosphere, atmosphere and biosphere. It is a key issue to understand the structural characteristics and soil carbon (C) cycle of the LCZ. We summarized the mechanisms of C exchange between rocks and the atmosphere, and discussed the mechanisms of C stabilization and persistence of the LCZ. Due to the deep layer, C stocks of the CLZ could be underestimated. In light of the recent theory of microbial C pump, soil microorganisms play an important role in C cycle, however, the microbial function is not widely considered in C cycling model of the LCZ. For future studies, it is suggested to systematically study the C cycling process from plant canopy to bedrock by the framework system of the LCZ. A variety of techniques and methods are integrated to combine short-term and high-frequency observations with long-term positioning observations, and pay attention to the response and feedback mechanisms of soil organic C (SOC) cycling to global changes and human activities, especially the migration and transformation of SOC in each circle and interface of the LCZ. We also recommend the necessity for intensive and long-term C monitoring in LCZ over broad geographic scale, to improve microbial C model for accurately evaluating terrestrial C budget and its dynamics. Altogether, this is the first review of C cycling, spanning from the land surface down to the bedrock in the LCZ, which is significant implications for biogeochemical cycling of C in surface and deep layers down to the bedrock.

Perovskite/c-Si tandem solar cell (TSC) has gradually become the hottest research topic in photovoltaic field for global carbon neutrality. Here we review the recent progress of numerical simulation studies of monolithic perovskite/c-Si TSC in terms of the methodology, light harvesting management, and energy yield aspects. It is summarized that the integration of physical fundamentals of the methodology, optimization of modeling and parameter correction can bring simulation results closer to experiments. Based on theoretical analysis of light harvesting management, we have demonstrated that textures can enhance light trapping capability and resonance absorption. The advances of bifacial perovskite/c-Si TSC have been particularly reviewed in simulation calibration (current matching loss approach) and low-cost strategy (ultrathin Si). Finally, through the energy yield analysis of the monofacial and bifacial TSC, we have innovatively proposed that spectral variables, effective albedo and top-cell bandgap should be integrated into cell preparation and module installation. This in-depth numerical simulation review provides a guidance for experimental preparation of low-cost and high-efficiency perovskite/c-Si TSC.

After a decade of planning and trials, China officially launched a national carbon trading in July 2021. Using a standard economic model, this study shows that an unconstrained carbon trading market would face a dilemma between minimizing pollution control costs and maximizing social benefits. We further show that this would be a significant challenge in China. Our results show that areas with higher population densities also would have higher costs for carbon reduction, and hence the polluters in those areas would be net buyers in the national market. Moreover, our analysis indicates a significantly high correlation between carbon dioxide emissions and other local pollutants. Therefore, cross-regional transactions may result in more emission of other pollutants in areas with higher population density under the unconstrained national cap-and-trade system and cause larger losses in social benefits. We call for more studies to address the issue.

Regarding the carbon neutrality target, the proportion of renewable energy in global energy sources is predicted to increase to 50% by 2050, and the increment in penetration requires fossil fuel power plants to play a key role in grid peak regulation. The integrated gasification combined cycle (IGCC) is a promising peak-regulating method for power grids. However, due to the strong coupling between units, the flexibility of gas turbines cannot be fully utilized in response to power demand. This paper proposed a novel polygeneration system integrating syngas storage, hydrogen production, and gas turbines for power. Through syngas storage, the dynamic characteristic of each unit can be decoupled to take advantage of the flexibility of the gas turbine. Compared to the general IGCC system, the load change rate of the new system could be increased from 0.5%/min to 3-5%/min without altering the dynamic characteristics of the original equipment. The design capacity of the syngas storage tank could be reduced by decreasing the ramp rate of the power generation unit or increasing the load change rate of the gasification and hydrogen production units. For the new 300-MW system, the required syngas storage tank capacity reached only approximately 1872 m³ under storage conditions of 35 bar and 25 °C. Furthermore, the investment in the syngas storage tank only accounted for approximately 6.6% of the total investment cost. In general, the novel system can be more flexibly operated under variable loads with low carbon emissions, which can help to increase the penetration of renewable energy in the power grid.

Thermal-integrated pumped thermal electricity storage (TI-PTES) could realize efficient energy storage for fluctuating and intermittent renewable energy. However, the boundary conditions of TI-PTES may frequently change with the variation of times and seasons, which causes a tremendous deterioration to the operating performance. To realize efficient and flexible energy storage in operating conditions, a novel composition-adjustable TI-PTES is proposed, and the operating performance is investigated and compared with composition-fixed TI-PTES. Simulation results show that, compared to composition-fixed TI-PTES, the energy storage efficiency of TI-PTES could be enhanced by the absolute value of 4.4-18.3% by introducing composition adjustment method under various boundary conditions. Besides, tuning sub-system composition could simultaneously adjust the capacities of power input, heat storage and power output, realizing a more flexible operating range for TI-PTES. A case study for an isolated energy community shows that composition-adjustable TI-PTES could realize 100% conversion of off-peak electric energy and reduce daily investment by 35.6% compared with composition-fixed TI-PTES.

The utilization of biochar derived from biomass residue to enhance anaerobic digestion (AD) for bioenergy recovery offers a sustainable approach to advance sustainable energy and mitigate climate change. However, conducting comprehensive research on the optimal conditions for AD experiments with biochar addition poses a challenge due to diverse experimental objectives. Machine learning (ML) has demonstrated its effectiveness in addressing this issue. Therefore, it is essential to provide an overview of current ML-optimized energy recovery processes for biochar-enhanced AD in order to facilitate a more systematic utilization of ML tools. This review comprehensively examines the material and energy flow of biochar preparation and its impact on AD is comprehension reviewed to optimize biochar-enhanced bioenergy recovery from a production process perspective. Specifically, it summarizes the application of the ML techniques, based on artificial intelligence, for predicting biochar yield and properties of biomass residues, as well as their utilization in AD. Overall, this review offers a comprehensive analysis to address the current challenges in biochar utilization and sustainable energy recovery. In future research, it is crucial to tackle the challenges that hinder the implementation of biochar in pilot-scale reactors. It is recommended to further investigate the correlation between the physicochemical properties of biochar and the bioenergy recovery process. Additionally, enhancing the role of ML throughout the entire biochar-enhanced bioenergy recovery process holds promise for achieving economically and environmentally optimized bioenergy recovery efficiency.

With the widespread popularity of carbon neutrality, the decarbonization approach using carbon capture, utilization, and storage (CCUS) has grown from a low-carbon utilization technology to an indispensable technology for the entire global carbon-neutral technology system. As a primary method to support CCUS research, source-sink matching models face several new demand-oriented challenges. Comprehensive research and in-depth insights are needed to guide targeted capability upgrades. This review evaluates the advances, challenges, and perspectives of various CCUS source-sink matching models developed in the past 10 years. We provide an integrated conceptual framework from six key attributes relating to mitigation targets, carbon sources, carbon sinks, transportation networks, utilization, and integration (synergy). The results indicate that previous models have effectively deepened our understanding of the matching process by targeting various CCUS-related issues and provided a solid foundation for more robust models to be developed. Six perspectives are put forward to outline research and development prospects for future models, which may have meaningful effects for advancement under emerging carbon neutrality targets.

The carbon reduction effect of bio-based levulinic acid chemicals is a matter of concern. This work reports the life cycle assessment of methyl levulinate based on local biomass refineries in China. The final LCA results showed that the entire life cycle of methyl levulinate could reduce by approximately 24% of carbon emissions compared with fossil diesel of equal quality. To address the lack of effective uncertainty analysis in current LCA research on levulinic acid chemicals, this study conducted a comprehensive and detailed assessment of inventory data and utilized Taylor series expansion to obtain uncertainty of the LCA results. When connected to a localized background database, the LCA results showed high credibility. According to the sensitivity analysis and Aspen optimization results, further technical improvement schemes are proposed, including improving thermal efficiency, use of clean electricity, and use of clean methanol. Prospective analysis shows that combined implementation of the above strategies can further reduce the existing carbon emissions by more than half.

Layered metal oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacity and wide Na⁺ diffusion channels. However, the irreversible phase transitions and cationic/anionic redoxes cause fast capacity decay. Herein, P2-type Na_0.67Mg_0.1Mn_0.8Fe_0.1O₂ (NMMF-1) cathode material with moderate active Fe³⁺ doping has been designed for sodium storage. Uneven Mn³⁺/Mn⁴⁺distribution is observed in NMMF-1 and the introduction of Fe³⁺ is beneficial for reducing the Mn³⁺ contents both at the surface and in the bulk to alleviate the Jahn-Teller effect. The moderate Fe³⁺/Fe⁴⁺ redox can realize the best tradeoff between capacity and cyclability. Therefore, the NMMF-1 demonstrates a high capacity (174.7 mAh g⁻¹ at 20 mA g⁻¹) and improved cyclability (78.5% over 100 cycles) in a wide-voltage range of 1.5-4.5 V (vs. Na⁺/Na). In-situ X-ray diffraction reveals a complete solid-solution reaction with a small volume change of 1.7% during charge/discharge processes and the charge compensation is disclosed in detail. This study will provide new insights into designing high-capacity and stable layered oxide cathode materials for SIBs.