A Water‐Splitting System with a Cobalt (II,III) Oxide Co‐Catalyst‐Loaded Bismuth Vanadate Photoanode Along with an Organo‐Photocathode
Takahiro Murakami, Kosuke Ikezoi, Keiji Nagai, Hideki Kato, Toshiyuki Abe
Abstract
Abstract In the water‐splitting reaction, the oxidation of water to O 2 is considered to be a kinetically demanding process, so that a co‐catalyst has been usually applied to promote water oxidation. This work demonstrates that, when loading mixed‐valence cobalt (II,III) oxide (Co 3 O 4 ) dispersed in a Nafion membrane (Nf) on a nanoporous bismuth vanadate (BiVO 4 ) photoanode (i. e., BiVO 4 /Nf[Co 3 O 4 ]), stable and efficient water oxidation occurred. In particular, it is noteworthy that the BiVO 4 /Nf[Co 3 O 4 ] photoanode exhibited stable performance even in an acidic medium (pH=2). In the present system consisting of a BiVO 4 /Nf[Co 3 O 4 ] photoanode along with an organo‐photocathode, the stoichiometric formation of O 2 and H 2 successfully occurred by applying just 0.1 V between the photoelectrodes (cf. maximum efficiency, ca. 0.2 %), which was superior to the prototype comprising BiVO 4 and Pt counter electrode. The Co 3 O 4 loading can effectively suppress the collapse of the nanostructured BiVO 4 upon photocorrosion, resulting in the stable and kinetically efficient consumption of holes in BiVO 4 .