Electric-Double-Layer Mechanism of Surface Oxophilicity in Regulating the Alkaline Hydrogen Electrocatalytic Kinetics

Regulating the surface oxophilicity of the electrocatalyst is known as an efficient strategy to mitigate the order-of-magnitude kinetic slowdown of hydrogen electrocatalysis in a base, which is of great scientific and technological significance. So far, its mechanistic origin remains mainly ascribed to the bifunctional or electronic effects that revolve around the catalyst-intermediate interactions and is under extensive debate. In addition, the understanding from the perspective of interfacial electric-double-layer (EDL) structures, which should also strongly depend on the electrode property, is still lacking. Here, by decorating a Pt electrode with Mo, Ru, Rh, and Au metal atoms to tune surface oxophilicity and systematically combining electrochemical activity tests, in situ surface-enhanced infrared absorption spectroscopy, density functional theory calculation, and ab initio molecular dynamics simulation, we found that there exist consistent volcano-type relationships between *OH adsorption strength and alkaline hydrogen evolution activity, the stretching/bending vibration information on interfacial water, and the potential of zero charge (PZC) of the electrode. This demonstrates that the origin of surface oxophilicity in impacting the alkaline hydrogen electrocatalytic activity lies in its modification toward the electrode PZC, which thereby dictates the electric field strength, rigidity, and hydrogen bonding network structure in EDL and ultimately governs the interfacial proton transfer kinetics. These findings emphasize the importance of focusing on electrocatalytic interface structures to understand electrode property-dependent reaction kinetics.