Transforming waste to energy: nanocatalyst innovations driving green hydrogen production

Abstract The burgeoning global demand for energy, coupled with the pressing need to mitigate carbon emissions, underscores the necessity for clean and sustainable energy alternatives, with green hydrogen emerging as a pivotal energy vector. Among the promising avenues for the production of green hydrogen, nano-catalysts derived from waste materials are attracting considerable interest due to their capacity to diminish production costs and environmental ramifications while capitalizing on underutilized waste streams. Notwithstanding recent advancements, significant knowledge deficits remain concerning the catalytic mechanisms, established performance benchmarks, and thorough sustainability evaluations of these materials. This review integrates contemporary progress in the synthesis, structural enhancement, and application of nano-catalysts originating from a variety of waste sources, including industrial byproducts, agricultural residues, and municipal waste. Crucial mechanistic variables, such as augmented active site density, improved electron transfer, and metal-support interactions, are examined to elucidate their superior performance in the hydrogen evolution reaction (HER). Comparative assessments utilizing standardized metrics (e.g., overpotential at 10 mA/cm 2 , Tafel slope, Faradaic efficiency) indicate that optimized waste-derived catalysts can realize up to a 30 % enhancement in hydrogen yield in comparison to traditional catalysts. Life cycle assessments (LCA), framed within cradle-to-gate methodologies, reveal substantial reductions in CO 2 emissions, energy consumption, and resource depletion. The review further delineates challenges associated with material variability, long-term durability, and the integration of these materials into pre-existing systems. Ultimately, this study highlights the crucial role of waste-derived nano-catalysts in promoting scalable, economically viable, and environmentally sustainable hydrogen production and advocates for enhanced interdisciplinary research and supportive policy frameworks to expedite their commercialization.