High efficiency oxygen evolution reaction enabled by 3D network composed of nitrogen-doped graphitic carbon-coated metal/metal oxide heterojunctions

The ability to develop low-cost highly efficient electrocatalyst for oxygen evolution reaction (OER) is key to the overall water splitting device that represents a viable and promising source of alternative energy. Herein, we crafted three-dimensional (3D) network comprising nitrogen-doped graphitic carbon-coated heterojunctions (denoted NC-Ni0.36Fe0.64/MnOx) via one-step calcination of hybrid precursors containing ternary Prussian blue analogues and polymers. The NC-Ni0.36Fe0.64/MnOx nanocomposites were then exploited as catalysts for OER, displaying exceptional performance with a small overpotential of 300 mV to reach 10 mA cm−2, a low Tafel slope of 43 mV/dec and an outstanding stability without deactivation over a 10-h OER. Notably, compared to commercial RuO2 catalysts, NCNi0.36Fe0.64/MnOx catalysts demonstrated much lower overpotential and Tafel slope. The excellent OER performance can be attributed to the presence of high-valence oxidized metal species (Ni2+, Fe2+ and Mn2+) at the heterostructured interface as well as pyridinic N-doped carbon species on highly conductive graphitic carbon network, thus greatly facilitating the electron-withdrawing from OH− and thus charge transfer during OER. This simple yet effective strategy may open new possibilities for creating a wide range of low-cost, high-efficiency, non-precious transition metal OER catalysts for the overall water splitting.