P-doped Ru-Pt Alloy Catalyst towards High Performance Alkaline Hydrogen Evolution Reaction
Electrocatalytic water splitting represents grand promise for hydrogen fuel in modern energy equipment and the design and fabrication of higher performance catalysts is at the central. Herein, we reported the sequential P-doping into Ru nanoparticles (Ru-P/C) by thermal annealing of Ru nanoparticles in PH3 atmosphere and deposition of extremely low concentration of Pt to obtain P-doped Ru-Pt alloy catalyst supported on carbon nanotubes, which is denoted as (Ru-P)#Pt/C. The X-ray diffraction and transmission electron microscopy show that ruthenium nanoparticles exist in the form of hexagonal close-packed (hcp) phase with low crystallinity. The high-resolution X-ray photoelectron spectroscopy results indicate that ruthenium is mainly in metallic state and Pt is slightly and positively charged, ascribing to the bonding with phosphorus atoms. This indicates that the highly diluted platinum atoms may be dispersed on the surface of Ru nanoparticles through Ru-P-Pt bonds. (Ru-P)#Pt/C alloy catalysts display excellent alkaline hydrogen evolution activity, which exhibits only 17 mV vs. RHE at a current density of 10 mA·cm–2 and a Tafel slope value of 27 mV·dec–1, superior to that of the control samples Ru-P/C and trace amount of Pt loaded P-doped CNTs (Pt/C-P). Density functional theory calculation (DFT) indicates that P-doping into Ru can enhance the adsorption of water molecules and the activation for water splitting, while the Pt site on Ru-Pt alloy behave as the hydrogen desorption site. Thus, the superior performance of (Ru-P)#Pt/C alloy catalyst might be to attributed to the synergistic effect of P-doped Ru sites and Pt sites, which significantly improves the alkaline hydrogen evolution reaction kinetics.