Unravelling the structure-activity relationship of porous binary metal-based electrocatalysts for green hydrogen evolution reaction

Green hydrogen (H₂) production through hydrogen evolution reaction (HER) via water splitting is deemed an efficient and sustainable fuel or energy carrier without environmental detriments. However, its higher cost remains the bottleneck in the commercialization process. Ubiquitously, porous binary metal-based catalysts so far remain the most active electrocatalysts for the HER, owing to their electronic effect, optimum hydrogen binding energy, and lower activation energies for H-desorption and recombination close to the thermodynamic potential. Despite plentiful efforts and developments, the engineering of porous binary metals for the HER still comprises numerous scientific problems to be unraveled, which still await deliberation. This review emphasizes the rational design of porous noble binary-metal-based electrocatalysts, porous transition binary-metal electrocatalysts (i.e., carbides/oxides, phosphides, chalcogenides) for the HER, both experimentally and theoretically (i.e., density functional theory (DFT) simulations and machine learning). Additionally, the associated mechanism, fundamental, and current interrogations (i.e., electronic effect, phase, strain, phase engineering, and interaction support) are highlighted related to porous bimetallic electrocatalysts for the HER. Eventually, a brief synopsis of the relevant milestones of current challenges and revitalizing perspectives to direct future research is presented aimed at developing effective porous binary metal-based electrocatalysts for large-scale HER applications.