Enhanced catalytic activity of polyoxometalate-based water oxidation catalyst through simple heat-treatment

Solar energy has attracted interest for clean hydrogen fuel from abundant water. However, because of water oxidation reaction with complex mechanism, it is necessary to develop efficient water oxidation catalysts (WOCs) to accelerate whole processes. Conventionally, ruthenium and iridium oxide has been introduced to facilitate catalytic electron extraction from water. The fact that they are rare and costly makes them impractical for application. Here, we report simple method to synthesize an efficient WOC from polyoxometalate ([Co4(H2O)2(PW9O34)2]10-, Co4POM) consisting of earth-abundant elements. It was found that simple annealing process under air atmosphere caused transformation to CoWO4-based WOC whose catalytic performance is significantly improved. Based on these results, we fabricated a-Fe2O3 (hematite) photoanode that showed significantly enhanced performance in terms of photocurrent and onset potential by integrating with Co4POM by layer-by-layer assembly and heat-treatment We believe that our novel approach can suggest simple way to synthesize efficient WOCs and to integrate them on photoelectrode universally