Hydrazine Hydrate Induced Two-Dimensional Porous Co³⁺ Enriched Co₃O₄ Nanosheets for Enhanced Water Oxidation Catalysis

Abstract

Herein, a hydrazine hydrate (N2H4) induced sacrificial template method is reported for controlled synthesis of 2D porous Co3O4 nanosheets (p-Co3O4 NSs) with adjustable thickness and abundant hierarchical pore structure. The introduction of N2H4 modulates the density of Co2+ anchored on the surface of GO by adjusting the number of oxygen functional groups for Co2+/GO composites and then controls the thickness and electronic valence of Co3O4 nanosheets during subsequent pyrolysis in air. As a result, the optimized 2D p-Co3O4 NSs have ultrathin thickness, abundant hierarchical porous structure, and a high Co3+/Co2+ ratio. As expected, it exhibits excellent OER catalytic performance in 1 M KOH solutions, affording a lower overpotential of 1.50 V at 10.0 mA cm–2 and robust stability compared to pristine Co3O4 and RuO2 as a benchmark. The outstanding OER catalytic activity is ascribed to its N2H4 induced ultrathin 2D structure with abundant hierarchical pores and a high Co3+/Co2+ ratio. The density functional theory (DFT) calculations reveal that the ultrathin layer Co3O4 nanosheets with a high ratio of Co3+/Co2+ enhance the OER activity through promoting the dissociation of water to OH* and accelerating kinetics of OER in alkaline media.