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

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 (Delta G0 (OH*)) 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 (similar to 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). [GRAPHICS] .

Automated summary

Amorphous catalysts have higher activity and selectivity compared to their crystalline counterparts due to their unique coordination unsaturated properties. This study reports the preparation of hybrids of graphene oxide supporting amorphous metal hydroxide through a solvent-controlled precipitation method. The investigation reveals that the electrocatalytic activity and selectivity of the catalyst are dependent on the coordinated metal catalytic sites and the disordered structure. In situ characterization techniques and density functional theory calculation confirm the importance of the degree of OH* poisoning in selective catalysis of oxygen reduction reaction for H2O2 production.