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 (Cu3N) 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 Cu3N 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 Cu3N 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 Cu3N 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.