Pre-intercalation of phosphate into Ni(OH)2/NiOOH for efficient and stable electrocatalytic oxygen evolution reaction

Layered Ni(OH)2/NiOOH hydroxides are effective oxygen evolution reaction (OER) electrocatalysts, but their activities are still inferior to those of benchmark RuO2 and IrO2. Notably, the long-term stability becomes a significant challenge. Herein, we present a novel volume OER (VOER) strategy to solve the problems via pre-intercalation of phosphate. Phosphate-intercalated Ni-Ni(OH)2/NiOOH electrode was prepared by a two-step electrochemical method. The obtained porous electrode exhibits outstanding OER performance in the alkaline phosphate electrolyte with the overpotentials of 129 and 243 mV at 10 and 100 mA cm−2, respectively, and stability for 1000 h. The exceptional performance is mainly ascribed to effective VOER and elimination of the interlayer-produced protons, because the phosphate-intercalation enhances the interlayer water content, interlayer spacing and proton transport ability, endows the interlayers with proton buffering capacity, and alters the chemical environment of the interlayer Ni-O. The finding provides a strategy to develop highly efficient and stable OER materials and reaction systems for layered transition metal hydroxides.