Hammett Substituent Constant Guided Design of Ligand‐Modified Ru Electrocatalyst for Hydrogen Evolution Reaction

Abstract The design of efficient alkaline hydrogen evolution reaction (HER) electrocatalysts is crucial for the development of green hydrogen production. In this work, we report modulation the HER activity of Ru nanoparticles by functionalization using para‐substituted phenylacetylenes (R = Cl, H, C 2 H 5 , and OCH 3 ), which have different electron donating/withdrawing capabilities. A close correlation between the Hammett substituent constant of the phenylacetylenes and HER activity of the functionalized Ru nanoparticles is revealed, and the underlying mechanism is investigated. Guided by such correlation, 4‐ethylphenylacetylene‐modified Ru nanoparticles (Ru─EPA) with a low HER overpotential of 17.7 mV at the current density of 10 mA cm −2 in alkaline solution is developed. The mechanistic understanding gained in this work will provide important guidelines for future development of high‐performance nanostructured electrocatalyst.