Atomizing platinum for hydrogen electrode reactions

Abstract

Anion exchange membrane fuel cells and water electrolyzers are promising hydrogen energy conversion devices due to more abundant options toward catalysts under alkaline conditions. However, the sluggish hydrogen electrode reaction kinetics remains a major challenge for wide applications. Herein, we conceive atomically dispersed Pt on Ni single-atom/nitrogen-doped carbon (PtA/C-Ni-NC), in which the Pt co-exists in Pt single atoms (PtA-N4 sites) and atomically dispersed Pt clusters (PtC). Such a multi-atom scale PtA/C-Ni-NC structure greatly enhances the active site density and atomic utilization by balancing hydrogen adsorption energy and hydroxyl adsorption energy, leading to significantly elevated hydrogen oxidation and evolution reactions (HOR/HER) catalysis activity. For HOR, it reaches a current density of 3.75 mA cm−2 at a potential of 200 mV, with a mass activity of 72.3 mA mg−1, which is 3 times higher than that of commercial Pt/C. For HER, to deliver the current density of 10 mA cm−2, the overpotential is only 10 mV, with a mass activity of 2217.7 mA mg−1, which is 8.4 times higher than that of commercial Pt/C. Density functional theory (DFT) calculations and in-situ detection results further confirm that the equilibrium between hydrogen binding energy (HBE) and hydroxyl binding energy (OHBE), and the unique interfacial water on the catalyst surface are responsible for high activity of the catalyst. This work provides important insights into developing multi-atom scale catalysts for efficient hydrogen electrode reactions and deeper understanding active sites dispersed at the atomic level.