  A well-established procedure for the photoelectrochemical (PEC) splitting of
water relies on using porous electrodes of WO3 sensitized with BiVO4 as a
visible scavenger photoanode semiconductor. In this work, we propose an evolved
photoelectrode fabricated by a soft-template approach consisting of supported
multishell nanotubes (NTs). These NTs are formed by a concentric layered
structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final film
of cobalt phosphate (CoPi) co-catalyst. Photoelectrode manufacturing is easily
implemented at large scale and combines thermal evaporation of single
crystalline organic nanowires (ONWs), magnetron sputtering (for ITO and WO3),
solution dripping, and electrochemical deposition processes (for BiVO4 and
CoPi, respectively) plus annealing under mild conditions. The obtained NT
electrodes depict a large electrochemically active surface and outperform by
more than one order of magnitude the efficiency of equivalent planar-layered
electrodes. A thorough electrochemical analysis of the electrodes under blue
and solar light illumination demonstrates the critical role of the WO3/BiVO4
Schottky barrier heterojunction in the control of the NT electrode efficiency
and its dependence on the BiVO4 outer layer thickness. Oxygen evolution
reaction (OER) performance was maximized with the CoPi electrocatalyst,
rendering high photocurrents under one sun illumination. The reported results
demonstrate the potential of the soft-template methodology for the large area
fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes, or
other alternative combinations, for the photoelectrochemical splitting of
water.
