Photoelectrochemical Water Splitting with ITO/WO 3 /BiVO 4 /CoPi Multishell Nanotubes Enabled by a Vacuum and Plasma Soft-Template Synthesis.

A common approach for the photoelectrochemical (PEC) splitting of water relies on the application of WO 3 porous electrodes sensitized with BiVO 4 acting as a visible photoanode semiconductor. In this work, we propose a new architecture of photoelectrodes consisting of supported multishell nanotubes (NTs) fabricated by a soft-template approach. These NTs are formed by a concentric layered structure of indium tin oxide (ITO), WO 3 , and BiVO 4 , together with a final thin layer of cobalt phosphate (CoPi) co-catalyst. The photoelectrode manufacturing procedure is easily implementable at a large scale and successively combines the thermal evaporation of single crystalline organic nanowires (ONWs), the magnetron sputtering deposition of ITO and WO 3 , and the solution dripping and electrochemical deposition of, respectively, BiVO 4 and CoPi, plus the annealing in air under mild conditions. The obtained NT electrodes depict a large electrochemically active surface and outperform the efficiency of equivalent planar-layered electrodes by more than one order of magnitude. A thorough electrochemical analysis of the electrodes illuminated with blue and solar lights demonstrates that the characteristics of the WO 3 /BiVO 4 Schottky barrier heterojunction control the NT electrode efficiency, which depended on the BiVO 4 outer layer thickness and the incorporation of the CoPi electrocatalyst. These results support the high potential of the proposed soft-template methodology for the large-area fabrication of highly efficient multishell ITO/WO 3 /BiVO 4 /CoPi NT electrodes for the PEC splitting of water.