Industrial Alkaline Electrolyzers Enabled by Interface-Engineered Cobalt Oxide Electrodes for High-Efficiency Water Splitting.

Alkaline (ALK) electrolysis is an important means to generate green hydrogen from water splitting, and its technical advance hinges critically on the breakthrough of catalytic electrodes capable of high current densities at low overpotentials. Here, an efficient and robust hydrogen-evolving electrode is developed, composed of cobalt oxide (CoO) nanosheet catalyst with a metal cobalt transition interface on the current-collecting nickel wire mesh substrate. This CoO electrode affords a unique charge avalanche effect at the metal-semiconductor interface to concentrate electron release and thus enables high-current-density hydrogen evolving at 1000 mA cm with only 207 mV overpotential, far outperforming commercial Raney nickel electrode that commonly delivers current densities below 500 mA cm at 300-500 mV overpotentials. An industrial cell-stack electrolyzer utilizing CoO electrodes achieves a consistent current density of 1000 mA cm at a 2.0 V cell voltage, surpassing the operational current density of commercial ALK systems by two to five times (200-500 mA cm). A significant enhancement in current output and a minimal deactivation rate of only 0.056 mV h demonstrate the potential of the CoO electrode to replace commercial Raney nickel electrode, thereby substantially improving the hydrogen production efficiency of ALK electrolyzers.