Ultra-low loading Pt atomic cluster electrode with Pt–O bond as an active site with high hydrogen evolution reaction performance

Abstract

Water electrolysis is the most fascinating procedure for producing pure hydrogen owing to its flexibility and convenience. Platinum (Pt) is the most effective electrocatalyst for the hydrogen evolution reaction (HER) but its high price and scarcity have greatly restricted its commercial application. Therefore, it is necessary to greatly increase the mass activity (MA) of Pt to meet practical applications. In the present study, an oxidized Pt atomic cluster-supported Au electrode (Pt_AC–O–Au) with an ultra-low loading was prepared by high vacuum magnetron sputtering combined with electrochemical anodic oxidation. The (Pt_AC–O–Au)-1 electrode has a very high mass activity (MA), reaching 49.2 A mg_Pt⁻¹ at an overpotential of 50 mV, which is 41 times that of the 20 wt% Pt/C electrode and 20 times that of the 0.5 wt% Pt/C electrode. Even at such a low load, the (Pt_AC–O–Au)-1 electrode has excellent apparent activity and only needs an overpotential of 41 mV@10 mA cm⁻², which is close to that of the 20 wt% Pt/C electrode (37 mV@10 mA cm⁻²). Moreover, the (Pt_AC–O–Au)-1 electrode has an ultra-high specific activity (SA). The SA of (Pt_AC–O–Au)-1 is 12–18 times higher than that of the 0.5 wt% Pt/C electrode and 36–56 times higher than commercial Pt/C electrodes. More importantly, it was confirmed by the electrochemical analysis method (cyclic voltammetry and CO adsorption–stripping) and X-ray photoelectron spectroscopy (XPS) that the active site is the oxidized platinum (Pt–O–Au) on the surface of the electrode. Density functional theory (DFT) calculations have also elucidated that the absolute value of ΔG_H*(Pt) of Pt_AC–O–Au is close to that of Pt(111), indicating that its outstanding HER activity originates from its optimal ΔG_H*(Pt) value.