Unravelling the HER activity of functionalized biochar: a pathway to cost-effective electrocatalysis

Abstract

The hydrogen evolution reaction (HER) stands at the forefront of green energy technologies, yet its dependence on costly noble metal catalysts often constrains its scalability. Biochar, a carbon-rich material derived from biomass pyrolysis, has emerged as a versatile, sustainable, and cost-effective material for use in HER electrocatalysis. This review comprehensively explores the synthesis, physicochemical properties, and catalytic potential of biochar, particularly when functionalized with heteroatoms or transition metals. Emphasis is placed on how structural attributes, such as high surface area, tunable porosity, and inherent conductivity, enhance the HER performance. Various biomass sources, including plant, animal, and industrial waste, are explored for their influence on the properties of biochar. Moreover, heteroatom doping and metal incorporation are critically examined for their role in optimizing electron transfer, increasing active site density, and reducing overpotential. The review concludes with an evaluation of biochar's environmental benefits, highlighting its alignment with circular economy principles and its potential to replace noble metal-based materials in electrocatalytic systems. This synthesis of current advancements establishes biochar as a promising platform for the scalable and eco-friendly production of hydrogen.