Compressive Strain Reduces the Hydrogen Evolution and Oxidation Reaction Activity of Platinum in Alkaline Solution

Abstract

It is unclear why the hydrogen evolution and oxidation reactions (HER/HOR) of platinum (Pt) are much slower in base than in acid. Neither is it clear why the sluggish HER/HOR of Pt in a base can be improved by mixing Pt with some transition metals. Herein, we constructed dealloyed carbon-supported Pt–Cu nanoclusters (D-PtCu3/C) with a core–shell Cu@Pt structure wherein the Pt–Cu alloying core is surrounded by Pt shells as a model HER/HOR catalyst to interpret these puzzles. Combined microscopy and in situ X-ray absorption spectroscopy verified the Cu@Pt structure in association with the compressive strain in D-PtCu3/C during the HER/HOR. The superior oxygen reduction reaction activity of the D-PtCu3/C to that of Pt/C in both acid and alkaline solution confirmed that the compressive strain weakens the Pt–O binding energy (EPt–O) of the D-PtCu3/C. The D-PtCu3/C with compressed Pt shells exhibited inferior HER/HOR activity and a positive shift of the sharp hydrogen adsorption/desorption peaks toward higher potential in comparison with Pt/C in alkaline solution. These results verified that the compressive strain reduces the HER/HOR activity of Pt by weakening EPt–O. This conclusion indicates that the HER/HOR kinetics of Pt in a base is mainly limited by the overly weak EPt–O rather than overly strong Pt–H binding energy.