Metal Nanoparticles Supported on Hexagonal Boron Nitride Nanosheets as an Efficient Catalysts for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a crucial step in the electrochemical water-splitting process that can be used as a competitive and sustainable method for clean energy production, energy storage, and electrochemical sensing applications. However, due to the commonly sluggish kinetics of the OER steps, newer catalytic materials that can lower the reaction overpotential are pivotal to enhance the overall OER efficiency. In this work, ultrathin hexagonal boron nitride (hBN) nanosheets fabricated by a molten metal assisted intercalation method is used as the supporting structure for metal nanoparticle deposition, then employed as efficient catalyst material for OER in alkaline environments. Different metals and metal combinations including Pt, Pd, Ru, Fe, Ni, NiFe, PtAg, and PdAg are tested in these catalyst systems as dopant materials. Aligning with the goal of using non-precious metal-based catalysts as the alternative to the current benchmarks of Ir and Ru based OER catalysts, our hBN supported Fe nanoparticle sample exhibited competitive electrochemical performance and low overpotential. Additionally, annealing of the hBN supported Fe sample in Ar at 800°C showed further improvements of such catalytic activity and an increased current density. High-resolution transmission electron microscopy (HRTEM) was done to reveal the structural and crystallinity characteristics of the metallic nanoclusters and/or atomically dispersed metal atoms confined on the hBN framework. X-ray photoelectron spectroscopy (XPS) is carried out to characterize the changes of chemical valence state of the dopant metals before and after annealing to offer more insights into the OER reaction mechanism. Electrochemical cycling testing was conducted to evaluate the stability of the metal-doped hBN catalysts that could be applied to hydrogen fuel cells and/or metal-air batteries.