In Situ Formation of Nanostructured Core–Shell Cu3N–CuO to Promote Alkaline Water Electrolysis

Electrochemical splitting of water to oxygen and hydrogen using earth-abundant first-row transition metal-based catalysts is a promising approach for sustainable energy conversion. Herein, we present a new convenient synthesis of copper nitride (Cu 3 N) that acts as a bifunctional electro(pre)catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water electrolysis in alkaline media. Strikingly, the electrophoretically deposited Cu 3 N on nickel foam (NF) displayed extremely low overpotentials for both OER and HER, and the overall water splitting cell potential was merely 1.62 V with a remarkable durability of over 10 days. Most notably, the coordinatively unsaturated Cu in Cu 3 N transformed in situ under a reducing environment and in an oxidative environment into a copper-rich shell that serves as the active site over an equally important electrically conductive Cu 3 N core to drive proficient catalysis. To the best of our knowledge, this is the first report on copper nitride for efficient and durable alkaline water electrolysis.