Green hydrogen: The fuel of tomorrow or a challenge of today?

Hydrogen fuel is a promising, eco-friendly renewable energy source that could replace conventional fossil fuels and have a significant impact on the energy supply chain. In the past 2 decades, extensive research and development have led to the emergence of hydrogen fuel-driven automobiles. Over the last 10 years, about 157 review articles have been published in the literature. However, existing literature has primarily focused on individual aspects of green hydrogen, such as production, storage, and transportation techniques, but lacks a comprehensive analysis of the interconnected challenges and solutions across the entire value chain. This comprehensive review focuses on the color spectrum of hydrogen and emphasizes upon the relationship between different hydrogen fuels and their catalytic activity. It also covers green hydrogen production methods, including electrolysis, photolysis, and biomass gasification, as well as proven hydrogen storage and transportation technologies. Additionally, an overview of different strategies adopted for developing efficient catalysts for photocatalysis and electrocatalysis is provided. A detailed discussion on crucial processes involved in photocatalysis and electrocatalysis, such as the hydrogen evolution reaction and oxygen evolution reaction, is also provided. This review article concludes with an overview of major applications, challenges, and the future potential of green hydrogen.