Controlling Platinum Active Sites on Silver Nanoparticles for Hydrogen Evolution Reaction

Abstract

Growing Pt on Ag nanoparticles is a promising approach to forming catalysts that present active sites with both Pt and Ag available to improve the activity for the hydrogen evolution reaction (HER). By carefully controlling the concentration of a Pt precursor, the amount of Pt-decorated particles onto the Ag nanoparticles could be controlled to grow Pt islands between 0.6 and 1.5 nm. As a result, the relative amounts of the Ag−Pt active sites could be tuned. The smallest, 0.6 nm Pt islands on the Ag nanoparticle, with the highest ratio of Ag−Pt to Pt−Pt sites was found to have the highest activity and an accelerated Volmer step. DFT modeling showed that the improved performance was due to increased electron density on Pt from electron donation from neighboring Ag that leads to weaker Pt−H binding and the presence of more oxophilic Ag that can bind −OH on the active site that accelerates the water splitting.

Understanding the Role of Small Platinum Island Size on Crystalline Nickel Nanoparticles in Enhancing the Hydrogen Evolution Reaction

“…This indicates that the rate-determining step (RDS) for all of the samples is the Volmer step, which is consistent for most Pt-based catalysts in alkaline HER. ,, The same RDS means that HER is limited by the water dissociation step across all of the samples in this case; however, the decreasing Tafel slope indicates faster reaction kinetics that is associated with the decrease of Pt island size from 1.7 to 1.0 nm. This faster kinetics is ascribed to a higher ratio of Pt–Ni to Pt–Pt active sites on the smaller islands, which has previously been shown to enable faster water dissociation due to the presence of Ni next to Pt. ,, …”