Amorphous Phosphates Tailor Local Proton Supply for Alkaline Hydrogen Evolution Electrocatalysis

Abstract

Hydrogen (H₂) is irreplaceable as a feedstock in varied industrial scenarios, and alkaline water electrolysis allows for H₂ production without costly proton exchange membrane and noble metals with limited reserves. However, alkaline solution is devoid of directly available protons, leading to suboptimal electrochemical H₂-evolving kinetics even on catalysts with high intrinsic activities like CoP. On the other hand, high local acidity (i.e., superfluous protons) can lead to undesirable catalyst corrosion and active site blocking by excessive hydrogen coverage. Herein, a “cobalt phosphate-clothed-CoP (CoPi@CoP)” nanoarray catalyst is developed for proof of concept to explore a possible proton supply design principle. The nanometer-thick amorphous CoPi appears to serve multiple functions: facilitating water dissociation/H–O cleavage, buffering excess protons, and accelerating proton transfer/donation, thus optimizing the local proton supply to H-consuming sites. As expected, CoPi@CoP demonstrates state-of-the-art hydrogen evolution reaction performance in alkaline electrolytes, surpassing that of intrinsically active CoP. Online differential mass spectrometry, dynamic potential decay transients, spectroscopy data, and theoretical calculations reveal possible (atomic scale) reaction mechanisms.