Sub-2 nm cobalt oxide cluster catalyst supported on alumina for efficient water oxidation

Abstract

Earth-abundant cobalt oxides as active water oxidation catalysts have attracted extensive attention, but the controlled synthesis of small cobalt oxide clusters still remains challenging. Herein we introduce a novel approach to deposit small cobalt oxide clusters on alumina which involves mild oxidation of molecularly dispersed Co4(CO)12 precursor. Scanning transmission electron microscope (STEM) shows that the size of prepared CoOx clusters is smaller than 2nm. Turnover frequency (TOF) value of water oxidation on the synthesized cobalt oxide clusters can reach as high as 0.067s−1 in photochemical Ru(bpy)32+-Na2S2O8 system, which is at least an order of magnitude higher than bulk cobalt oxide nanoparticles. The remarkably enhanced activity of cobalt oxide cluster is attributed to its more surface-exposed cobalt atoms and higher intrinsic activity.