The Enhancement of Selectivity and Activity for Two-Electron Oxygen Reduction Reaction by Tuned Oxygen Defects on Amorphous Hydroxide Catalysts

Abstract

Amorphous catalysts, thanks to their uniquely coordinated unsaturated properties and abundance of defect sites, tend to possess higher activity and selectivity than their crystalline counterparts. In this work, we report a facile and general solvent-controlled precipitation method to prepare hybrids of graphene oxide (GO) supporting amorphous metal hydroxide [A-M(OH)x/GO, M = Cu, Co, and Mn], which provides us with tangible materials to study the structure-performance relationship of various amorphous oxides. The systematic investigation of A-Cu(OH)2/GO by coupling ex situ/in situ characteristic techniques with electrochemical studies reveals that electrocatalytic activity and selectivity toward a two-electron oxygen reduction reaction (ORR) is highly dependent on the coordinated Cu catalytic sites and the disordered structure of A-Cu(OH)2. In situ X-ray absorption near-edge structure (XANES) and density functional theory (DFT) calculation verify that the degree of OH* poisoning (ΔG0OH*) tuned by three-OH-coordinated Cu sites in amorphous structures plays a crucial role in selective catalysis of ORR for H2O2 production. The optimized A-Cu(OH)2/GO shows superior activity and high selectivity (~95%) toward H2O2, as demonstrated by a zinc-air battery capable of on-site H2O2 production with a rate as high as 3401.5 mmol h−1 g−1