Is hydrogen a silver bullet in fighting climate change and recent trends in hydrogen technologies

This review article is not intended to audience that is specialized in the research and development as well as deployment of hydrogen technologies. Rather, it is for those who are in the fields of commercialization, investment and applications of new technologies, working in areas relevant to climate change and energy policies, as well as those who have a general interest in hydrogen energy. While hydrogen holds a bright future in reducing carbon emission and mitigating climate change, it is only one of the valid means among an integrated and diverse set of solutions. As part of the current effort for energy transition, hydrogen offers zero emission provided that the electricity used for generating hydrogen is from green sources. In the domain of producing green hydrogen, alkaline electrolysis (AE) currently dominates industrial applications thanks to its lower costs and reasonable efficiency, while it is expected proton exchange membrane (PEM) will pick up pace from 2030. Anion exchange membrane (AEM) is relatively new and may hopefully combine some of the advantages of both AE and AEM. However, each technology has its niche based on the application‘s specific requirements, such as cost sensitivity, purity needs, and operational flexibility. Producing hydrogen from biomass, including waste materials, is an area of active research and development and several technologies have been explored or under development for harnessing hydrogen from such resources. Manufacturing and applying more efficient and powerful electrolysers at lower costs is the way to go. While storing and shipping hydrogen in containers with hydrogen in a compressed gaseous or cryogenic liquified form remain the primary ways, solid-state storage of hydrogen is getting more and more attention, with metal hydrides such as MgH2, TiFeH₂, NaAlH₄, etc. getting close to full commercial applications. Dissolving hydrogen in organic solvents or converting it into ammonia, is a direction of on-going research. With a proper way for safe and low-cost storage of hydrogen in large scale, hydrogen as an energy carrier is a great candidate for grid balance. Although hydrogen can be used as a fuel directly such as with an internal combustion engine (ICE) or gas turbine, as well as used as a chemical reagent such as a reductant in steel making or as feedstock in a variety of industrial processes, a lot of attentions is paid to the use of hydrogen with fuel cells (FC). Current focuses on FC are reducing costs, adapting to harsher working conditions, enhancing flexibility and durability, increasing fuel types, finding more applications and scaling up. It is expected that the hydrogen industry will continue to attract large capital inflows in 2025 and beyond to achieve a low-carbon transition for energy-intensive sectors. Hydrogen infrastructures are being developed all over the world, with China seemingly leading the way. Transporting hydrogen by pipeline is important for developing a hydrogen economy, and demonstration projects are currently underway in many countries.