China, People’s Republic

Water splitting is an effective strategy to produce renewable and sustainable hydrogen energy. Especially seawater splitting avoiding use of the limited freshwater resource is more intriguing. Nowadays electrocatalysts explored for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) using natural seawater or saline electrolyte have been increasingly reported. To better understand the current status and challenges of the electrocatalysts for HER and OER from seawater we comprehensively review the recent advances in electrocatalysts for seawater splitting. The fundamentals challenges and possible strategies for seawater splitting are firstly presented. Then the recently reported electrocatalysts that explored for HER and OER from seawater are summarized and discussed. Finally the perspectives in the development of high-efficient electrocatalysts for seawater splitting are also proposed.

In this paper a two-layer optimization approach is proposed to facilitate the multi-energy complementarity and coupling and optimize the system configuration in an electric-hydrogen-integrated energy system (EH-IES). Firstly an EH-IES with virtual energy storage is proposed to reduce the cost of physical energy storage equipment. Secondly a two-layer optimal allocation method is proposed under a multi-timescale strategy to examine the comprehensive evaluation index of environmental protection and economy. The upper layer utilizes the NSGA-II multi-objective optimization method for system capacity allocation while the lower layer performs economic dispatch at the lowest cost. Ultimately the output includes the results of the equipment capacity allocation of the EH-IES that satisfies the reliability constraint interval and the daily scheduling results of the equipment. The results demonstrate that the electric-hydrogen-integrated energy system with the coupling of multiple energy equipment not only enhances the utilization of renewable energy sources but also reduces the usage of fossil energy and improves the system’s reliability.

Faced with a global consensus on net-zero emissions the use of clean fuels to entirely or substantially replace traditional fuels has emerged as the industry’s primary development direction. Alcohol–hydrogen fuels primarily based on methanol are a renewable and sustainable energy source. This research focuses on energy sustainability and presents a boiler fuel blending system that uses methanol–hydrogen combinations. This system uses the boiler’s waste heat to catalytically decompose methanol into a gas mostly consisting of H2 and CO which is then co-combusted with the original fuel to improve thermal efficiency and lower emissions. A comparative experimental study considering natural gas (NG) blending with hydrogen and dissociated methanol gas (DMG) was carried out in a small natural gas boiler. The results indicate that with a controlled mixed fuel flow of 10 m3/h and an excess air coefficient of 1.2 a 10% hydrogen blending ratio maximizes the boiler’s thermal efficiency (ηt) resulting in a 3.5% increase. This ratio also results in a 1% increase in NOx emissions a 25% decrease in HC emissions and a 5.66% improvement in the equivalent economics (es). Meanwhile blending DMG at 15% increases the boiler’s ηt by 3% reduces NOx emissions by 13.8% and HC emissions by 20% and improves the es by 8.63%. DMG as a partial substitute for natural gas outperforms hydrogen in various aspects. If this technology can be successfully applied and promoted it could pave a new path for the sustainable development of energy in the boiler sector.

This paper provides a systematic visualization of the development current status and challenges of salt cavern hydrogen storage technology based on the relevant literature from the past five years in the Web of Science Core Collection database. Using VOSviewer (version 1.6.20) and CiteSpace software (advanced version 6.3.R3) this study analyzes the field from a knowledge mapping perspective. The findings reveal that global research hotspots are primarily focused on multi-energy collaboration integration of renewable energy systems and exploration of commercialization highlighting the essential role of salt cavern hydrogen storage in driving the energy transition and promoting sustainable development. In China research mainly concentrates on theoretical innovations and technological optimizations to address complex geological conditions. Despite the rapid growth in the number of Chinese publications unresolved challenges remain such as the complexity of layered salt rock and thermodynamic coupling effects during highfrequency injection and extraction as well as issues concerning permeability and microbial activity. Moving forward China’s salt cavern hydrogen storage technology should focus on strengthening engineering practices suited to local geological conditions and enhancing the application of intelligent technologies thereby facilitating the translation of theoretical research into practical applications.

This paper focuses on the critical role of long-duration energy storage (LDES) technologies in facilitating renewable energy integration and achieving carbon neutrality. It presents a systematic review of four primary categories: mechanical energy storage chemical energy storage electrochemical energy storage and thermal energy storage. The study begins by analyzing the technical advantages and geographical constraints of pumped hydro energy storage (PHES) and compressed air energy storage (CAES) in high-capacity applications. It then explores the potential of hydrogen and synthetic fuels for long-duration clean energy storage. The section on electrochemical energy storage highlights the high energy density and flexible scalability of lithium-ion batteries and redox flow batteries. Finally the paper evaluates innovative advancements in large-scale thermal energy storage technologies including sensible heat storage latent heat storage and thermochemical heat storage. By comparing the performance metrics application scenarios and development prospects of various energy storage technologies this work provides theoretical support and practical insights for maximizing renewable energy utilization and driving the sustainable transformation of global energy systems.

Large-scale hydrogen (H2 ) production is an essential gear in the future bioeconomy. Hydrogen production through electrocatalytic seawater splitting is a crucial technique and has gained considerable attention. The direct seawater electrolysis technique has been designed to use seawater in place of highly purified water which is essential for electrolysis since seawater is widely available. This paper offers a structured approach by briefly describing the chemical processes such as competitive chloride evolution anodic oxygen evolution and cathodic hydrogen evolution that govern seawater electrocatalytic reactions. In this review advanced technologies in transition metal phosphide-based seawater electrolysis catalysts are briefly discussed including transition metal doping with phosphorus the nanosheet structure of phosphides and structural engineering approaches. Application progress catalytic process efficiency opportunities and problems related to transition metal phosphides are also highlighted in detail. Collectively this review is a comprehensive summary of the topic focusing on the challenges and opportunities.

The pressure to move to sustainable energy sources is obvious in today's fast changing energy environment. In this context green hydrogen appears as a beacon of hope with the potential to reinvent the paradigms of energy consumption particularly in the transportation and aviation sectors. Hydrogen has long been intriguing owing to its unique characteristics. It is not only an energy transporter; it has the power to alter the game. Its growing significance is due to its capacity to decarbonize energy generation. Traditional hydrogen generation techniques have contributed considerably to world CO2 emissions accounting for over 2% of total emissions. This environmental problem is successfully addressed by the development of green hydrogen which is created from renewable energy sources. The International Energy Agency (IEA) predicts a 25 to 30 percent increase in global energy consumption by 2040 which is a very grim scenario. If continue to rely on coal and oil this growing demand will result in greater CO2 emissions exacerbating climate change's consequences. In this situation green hydrogen is not only an option but a need. Because green hydrogen has properties with conventional fuels it can be simply integrated into current infrastructure. This harmonic integration ensures that the shift to hydrogen-based solutions in these sectors would not demand a complete redesign of the present systems assuring cost-effectiveness and practicality. However like with any energy source green hydrogen has obstacles. Its combustibility and probable explosiveness have been cited as causes for concern. However developments in safety measures have successfully mitigated these dangers ensuring that hydrogen may be used safely and efficiently across various applications. A further difficulty is its energy density particularly in comparison to conventional fuels. While its energy-to-weight ratio may be good its bulk poses challenges particularly in the aviation industry where space is at a premium. Beyond its direct use as a fuel green hydrogen has potential in auxiliary capacities. It may be used as a dependable backup energy source during power outages as well as in a variety of different sectors and uses ranging from manufacturing to residential. Green hydrogen's adaptability demonstrates its potential to infiltrate all sectors of our economy. Storage is an important enabler for broad hydrogen use. Effective hydrogen storage technologies guarantee not only its availability but also its viability as a source of energy. Current research and advancements in this field are encouraging which strengthens the argument for green hydrogen. At conclusion green hydrogen is in the vanguard of sustainable energy solutions particularly for the transportation and aviation industries. In our collaborative quest of a sustainable future its unique features and environmental advantages make it a vital asset. As we explore further into the complexities of green hydrogen in this publication we want to shed light on its potential obstacles and future route.

With the continuous development of hydrogen storage systems power-to-gas (P2G) and combined heat and power (CHP) the coupling between electricity–heat–hydrogen–gas has been promoted and energy conversion equipment has been transformed from an independent operation with low energy utilization efficiency to a joint operation with high efficiency. This study proposes a low-carbon optimization strategy for a multi-energy coupled IES containing hydrogen energy storage operating jointly with a two-stage P2G adjustable thermoelectric ratio CHP. Firstly the hydrogen energy storage system is analyzed to enhance the wind power consumption ability of the system by dynamically absorbing and releasing energy at the right time through electricity–hydrogen coupling. Then the two-stage P2G operation process is refined and combined with the CHP operation with an adjustable thermoelectric ratio to further improve the low-carbon and economic performance of the system. Finally multiple scenarios are set up and the comparative analysis shows that the addition of a hydrogen storage system can increase the wind power consumption capacity of the system by 4.6%; considering the adjustable thermoelectric ratio CHP and the twostage P2G the system emissions reduction can be 5.97% and 23.07% respectively and the total cost of operation can be reduced by 7.5% and 14.5% respectively.

For the safe and efficient utilization of hydrogen-enriched natural gas combustion in industrial gas-fired boilers the present study adopted a combination of numerical simulation and field tests to investigate its adaptability. Firstly the combustion characteristics of hydrogen-enriched natural gas with different hydrogen blending ratios and equivalence ratios were evaluated by using the Chemkin Pro platform. Secondly a field experimental study was carried out based on the WNS2- 1.25-Q gas-fired boiler to investigate the boiler’s thermal efficiency heat loss and pollutant emissions after hydrogen addition. The results show that at the same equivalence ratio with the hydrogen blending ratio increasing from 0% to 25% the laminar flame propagation speed of the fuel increases the extinction strain rate rises and the combustion limit expands. The laminar flame propagation speed of premixed methane/air gas reaches the maximum value when the equivalence ratio is 1.0 and the combustion intensity of the flame is the highest at this time. In the field tests as the hydrogen blending ratio increases from 0% to nearly 10% with the increasing excess air ratio the boiler’s thermal efficiency decreases as well as the NOx emission. This indicates that there exists a tradeoff between the boiler thermal efficiency and NOx emission in practice.

Unlike the typical low-temperature (< 150 °C) continental geothermal systems usually characterized by high N2 CH4 and CO2 concentrations but a trace H2 concentration the sandstone-dominated Jimo hot spring on China's eastern coast exhibits: (1) abnormally high H2 concentrations (2.4–12.5 vol%) and H2/CH4 (up to 46.5); (2) depleted δD-H2 (−822 to −709‰) comparable to the Kansas hot springs near the Mid-Continent rift system with the most depleted δD-H2 (−836 to −740‰) recorded in nature; and (3) dramatic gas concentration and isotope ratio variations within an area of 0.2 km2 . Gas chemistry and H-C-He-Ne isotope ratios are studied with reference to published H2 isotope data from various systems. The origin of the gas is most likely attributed to: (a) allochthonous abiotic H2 generated by the reduction of water and oxidation of FeII-rich pyroxene and olivine (serpentinization) in the basalt located 2 km away under near-surface conditions and migration to the deep sandstone reservoir; (b) primary thermogenic CH4 produced in the sandstone; (c) mixing with a considerable amount of microbial H2 from shallow fresh and marine sediments; and (d) biotic CH4 with typical abiotic signatures resulting from isotope exchanges with fluids high in H2/CH4 and CO2/CH4 ratios. Allochthonous abiotic H2 in a sandstone-dominated continental geothermal system and massive microbial fermentation-based H2 production in shallow fresh and residual marine sediments with insignificant but differential consumption activity are highlighted. The published hydrogen isotope ratios for H2 produced under various natural geological environmental and experimental conditions have been collected systematically to provide a fundamental framework and an initial tool for restricting the dominant origin of H2.