Highly active bimetallic Pt–Cu nanoparticles for the electrocatalysis of hydrogen evolution reactions: Experimental and theoretical insight

Abstract

Improving the activity and stability of Pt-based electrocatalysts is still crucial for hydrogen generation applications. In this study, we investigated the catalytic properties of Cu-doped Pt alloy nanostructures synthesized by the modified polyol method, and compared the performance of PtCu catalyst with that of commercially available Pt/C for the hydrogen evolution reaction (HER) at room temperature. Structural analyses revealed that the PtCu catalysts exhibited fcc-Fm3¯m crystal structure with an average particle size below 5 nm. The HER performance of the catalysts showed overpotential of around −1.0 V (vs. Ag/AgCl) and Pt0.25Cu0.75 and Pt0.75Cu0.25 catalysts exhibited enhanced performance in 1 M KOH. The Pt0.75Cu0.25 catalyst exhibited distinct performance, with the highest mass activity found to be 62.80 mA mg−1Pt. The most active Pt0.75Cu0.25 catalysis for the HER process had the lowest onset potential of 0.989 V and Tafel slope of 35.5 mV dec−1, which were an improvement compared to commercially available Pt/C catalysts. First principle DFT calculations confirmed the stabilities of Pt1Cu3, Pt1Cu1 and Pt3Cu1 compositions as ordered alloy structures. Nudged elastic band method calculations and the d-band model verified the higher catalytic activity of Pt–Cu nanoparticles compared to pure nanoparticles and point out the relevance of a synergistic effect of Pt and Cu atoms on water dissociation. According to DFT calculations, Cu and Pt sites significantly influenced the adsorption of H2O and H, respectively, for splitting water molecules. While the Pt59Cu20 cluster has the highest H2O adsorption energy at the (100) atop site of Cu atoms, H adsorption occurs at the (111) site of Pt atoms.