Ni3N-Scaffolded Amorphous Ni-Co-Mn Hydroxide/Oxyhydroxide Interfaces for Durable High-Current Alkaline Water...

Developing electrocatalysts that retain high activity under concentrated alkaline electrolyte, elevated temperature, and large current density remains challenging. Here, a hierarchical NiCoMn-NiN electrode was constructed by coupling a porous Ni3N framework with an amorphous Mn-containing Ni-Co hydroxide/oxyhydroxide-like coating. In 1.0 M KOH, the electrode requires overpotentials of 100 and 315 mV at 100 mA cm-2 for HER and OER, respectively. A symmetric NiCoMn-NiN||NiCoMn-NiN electrolyzer delivers 100 mA cm-2 at 1.68 V and operates stably for 168 h. In 30 wt % KOH at 80 °C, the electrode sustains 1000 mA cm-2 for more than 358 h with only minor potential variation. Structural analyses indicate a predominantly amorphous coating with short-range metal-oxygen coordination and electrochemically induced surface evolution after operation. Density functional theory (DFT) calculations further suggest that Mn incorporation alters the local electronic environment and adsorption energetics of key intermediates. These results demonstrate the suitability of NiCoMn-NiN for sustained high-current alkaline electrolysis.