In Situ Grown Cuboidal MnCo₂O₄/h Boron Nitride Heterojunction: A Noble Metal-Free Approach Based on Efficient Hole Extraction for Electrochemical Oxygen Evolution Reaction

Rational design of complex spinel oxides directly onto the substrate as a highly stable electrocatalytic anode material for oxygen evolution reaction (OER) is a crucial step to replace a noble metal-based electrocatalyst. Herein, surfactant-free cuboidal MnCo2O4 (C-MCO) was synthesized in situ over FTO by a green and simple synthetic protocol. Stable and good ohmic contact between C-MCO and the substrate ensures efficient transfer of the charge carrier at their interface. Hexagonal boron nitride (h-BN) nanosheets coupled with C-MCO provides a surface for easy deposition of the co-catalyst, making active sites easily available and accessible for enhanced OER activity. The surface-modified C-MCO/h-BN electrode shows a Tafel slope value of 66 mV/dec with an overpotential of 240 mV at a current density of 10 mA/cm2. C-MCO/h-BN displays ∼2.8-fold enhancement in turnover frequency compared to its pristine counterpart, with a faradaic yield of 97%. This study can be used for large-scale clean energy production owing to its low-cost, efficient, eco-friendly, and long-term stability of the C-MCO/h-BN electrocatalyst.