Synthesis of CoWO4 nanoparticles from polyoxometalates for stable photoelectrochemical water oxidation

Abstract

Here we report a novel method to synthesize CoWO4 using tetracobalt-substituted polyoxometalate (Co4POM) as a precursor and its application as an efficient and stable water oxidation catalyst (WOC). We found that amorphous and crystalline CoWO4 were readily formed by heat treatment of Co4POM at different temperatures and have different catalytic activity for oxygen evolution reaction (OER); amorphous CoWO4 shows higher catalytic activity than crystalline CoWO4. We also present a simple method to deposit insoluble CoWO4 WOCs on photoanodes such as hematite by layer-by-layer (LbL) self-assembly of polyelectrolytes and POM followed by annealing process. It was found that the deposition of CoWO4 WOCs leads to a significant improvement of photoelectrochemical performance of photoanodes in terms of OER onset potential and current density. We believe that our findings can provide a simple alternative way to synthesize and deposit efficient, stable WOCs such as CoWO4 on various photoelectrodes to improve their photocatalytic efficiency.