Recent advances in green hydrogen production, storage and commercial-scale use via catalytic ammonia cracking

Sustainable societal growth relies on the efficient storage, transportation, and use of renewable energies. Considerable progress has been made in sustainable hydrogen production via water electrolysis and biomass conversion, but hydrogen storage and transportation remain major challenges for commercial-scale applications. Owing to its high hydrogen content and energy density, ammonia is a promising zero-carbon energy carrier for large-scale energy storage. Therefore, the transformation of renewable hydrogen into ammonia is a promising strategy for effective hydrogen transportation and storage. Unlike the direct combustion of ammonia, which can produce NO_x, catalytic cracking into nitrogen and hydrogen provides an environmentally friendly method for hydrogen regeneration. Herein, recent advances in effective ammonia decomposition via various processes, including electrochemical, photochemical, and, particularly, thermochemical routes, are summarized. In addition, hydrogen separation techniques and techno-economic analyses of the ammonia and hydrogen economy are discussed. The main objective of this review is to provide a conceptual framework for effective ammonia cracking to yield pure hydrogen as a clean fuel for developing futuristic and sustainable energy solutions.