Ammonium cobalt phosphate with asymmetric coordination sites for enhanced electrocatalytic water oxidation

Abstract

Cobalt-based materials have been considered as promising candidates to electrocatalyze water oxidation. However, the structure-performance correlation remains largely elusive, due to the complex material structures and diverse performance-influencing factors in those Co-based catalysts. In this work, we designed two cobalt phosphates with distinct Co symmetry to explore the effect of coordination symmetry on electrocatalytic water oxidation. The two analogues have similar morphology, Co valence and 6-coordinated Co octahedron, but with different coordination symmetry. In contrast to symmetric Co 3 (PO 4 ) 2 ·8H 2 O, asymmetric NH 4 CoPO 4 ·H 2 O exhibited enhanced electrocatalytic water oxidation activity in a neutral aqueous solution. It is proven that, by experimental and theoretical studies, the asymmetric Co coordination sites can facilitate the surface reconstruction under anodic polarization to boost the electrocatalysis. Based on this contrastive platform with distinct symmetry differences, the preferred configuration in cobalt-oxygen octahedrons for water oxidation has been straightforwardly assigned. Two cobalt phosphates with distinct Co symmetry were obtained to explore the effect of coordination structure on the electrocatalytic oxygen evolution reaction. Asymmetric Co geometry can accelerate surface reconstruction to enhance OER activity.