Reconstruction-mediated interfacial water engineering in Cu-Mo electrocatalyst for highly efficient and durable water splitting

The development of efficient and durable electrocatalysts for industrial-level water splitting remains a critical challenge. Here we report a CuO-MoS2/MoO3 precatalyst that undergoes electrochemical reconstruction under working conditions to yield two distinct active phases: Cu-MoS2 for the hydrogen evolution reaction (HER) at the cathode and an optimized CuO-MoS2/MoO3 for the oxygen evolution reaction (OER) at the anode. In 1.0 M KOH, the reconstructed electrodes deliver remarkably low overpotentials of 35 mV for HER and 124 mV for OER at 10 mA cm-2, along with outstanding long-term durability, sustaining 500 mA cm-2 for 100 h. Combined in situ Fourier-transform infrared spectroscopy and density functional theory calculations reveal that Cu species not only enhance charge transport but also tailor the electronic structure to optimize intermediate adsorption and reorganize interfacial water into a strongly hydrogen-bonded network, thereby accelerating water dissociation and proton transfer kinetics. When assembled into an anion-exchange-membrane water electrolyzer, the system delivers 1.0 A cm-2 at a low voltage of 1.77 V and 80 °C, with stable operation for 500 h, substantially surpassing noble-metal benchmarks. Our findings offer an efficient and durable catalyst system for sustainable hydrogen production, as well as fundamental insights into catalyst reconstruction and interfacial water regulation that inform the rational design of electrocatalytic materials.