Atomically engineered cobalt-doped boron nitride nanosheets for the water oxidation reaction

Abstract

Hexagonal boron nitride (h-BN) is a fascinating two-dimensional material with a wide range of potential applications. However, its application in electrocatalysis is limited due to the lack of proper active sites and poor electrical conductivity. Herein, we introduce cobalt as a dopant into h-BN nanosheets using a controlled molten salt technique at elevated temperature. The structural and morphological analysis confirms the successful formation of h-BN and cobalt-doped BN nanosheets. The presence of cobalt in the h-BN nanosheets disrupts the extended π conjugation of h-BN by electronically interacting with B and N. The non-stoichiometric B/N ratio generated defect sites in h-BN, which enables the incorporation of cobalt into the lattice. While bare h-BN exhibits poor catalytic activity towards the oxygen evolution reaction (OER), cobalt doping significantly enhances its performance. The cobalt centers serve as the active sites for the OER, with the material containing 2.5 weight% cobalt (Co_2.5-BN) demonstrating optimized catalytic performance, demanding only 322 mV overpotential at 10 mA cm⁻² current density along with a robust stability for 50 hours. A turnover frequency (TOF) of 1.0 s⁻¹ at 400 mV overpotential highlights the high intrinsic activity of Co_2.5-BN. The in situ EIS analysis of Co_2.5-BN reveals fast OER kinetics with minimum energy input. This study utilizes the structural features of the h-BN material via cobalt doping towards enhanced OER catalysis.