Cobalt/Vanadium Nitride Nano-Heterojunction Supported on N-Doped Nanocarbon for Alkaline Overall Water Splitting

Abstract

Designing a structurally unique and highly active transition metal-based bifunctional electrocatalyst for alkaline water splitting remains challenging. Herein, a bifunctional electrocatalyst consisting of Co/VN nano-heterojunction anchored on nitrogen-doped carbon (NC) with three-dimensional porous carbon structures was successfully synthesized. Vanadium nitride (VN) can act as an intermediate “bridge” for electron transfer, receiving or supplying electrons; optimizing the charge transfer path on the surface of Co-NC materials; enhancing the electronic synergy between Co, VN, and NC; making the catalytic sites on NC more active; and achieving faster hydrogen evolution reaction (HER) kinetics. The conversion of the active site Co to cobalt oxides and hydroxides in the oxygen evolution reaction (OER) process has also been rapidly optimized under the action of the “sacrificial promoter” VN, providing more prosperous active sites at the heterojunction as VN dissolves. In an alkaline solution, the optimized Co/VN/NC-8 catalyst only requires 116 and 311 mV to provide a current density of 10 mA/cm² for HER and OER, respectively. Moreover, a low battery voltage of 1.74 V is required for overall water splitting to reach the current density of 10 mA/cm². This work provides a strong basis for interface engineering to regulate transition metals supported by carbon materials.