Correlating crystallinity regulation in spinel oxides and catalytic activity in electrocatalytic water oxidation

Recently, the electro-Fenton (EF) process by coupling cathodic two-electron oxygen reduction reaction (2e- ORR) with anodic oxygen evolution reaction (OER) has emerged as a potentially viable technology, while the sluggish OER is the main bottleneck. As promising OER catalysts, the amorphous and crystal phases of spinel oxides display high activities and electrical conductivity, respectively. Efforts to produce amorphous/crystal spinel oxides have progressed slowly, and how an amorphous/crystal structure benefits the catalytic performances remains elusive. Herein, Fe-doped NiCo2O4 (Fe-NiCo2O4) was used as a model catalyst to explore the effect mechanism of crystallinity controlled by annealing temperature on OER performance. The results display that the Fe-NiCo2O4 obtained at 300 degree celsius shows amorphous/crystal structure, which facilitates the active site exposure and the charge transfer, leading to superior OER activity and catalytic stability. Based on the crystallinity regulation of OER catalysts, we propose an anodic optimized strategy to upgrade the EF-related processes by effectively providing O2 produced in the anode.