Abstract

One standout technology for hydrogen production is water electrolysis, which has become widely adopted and firmly established. In conventional water electrolyzers, hydrogen generation occurs at the cathode by means of the hydrogen evolution reaction (HER) through a pH-dependent mechanism. This review article systematically explores and synthesizes the diverse range of descriptors that govern the HER. Beginning with an overview of the fundamental principles underlying the reaction, conventional HER key descriptors are described, including Gibbs free energy of hydrogen adsorption and the d-band center theory. Furthermore, recent advancements in the field are highlighted as novel descriptors for recently emerged topological catalysts, such as carbides and sulfides. With the goal of facilitating the development of efficient and economically viable electrocatalysts for HER and promoting a sustainable hydrogen economy, this review consolidates the existing knowledge landscape into a comprehensive resource for researchers and engineers.