Bendable BiVO-Based Photoanodes on a Metal Substrate Realized through Template Engineering for Photoelectrochemical Water Splitting.

Unlike planar photoelectrodes, bendable and malleable photoelectrodes extend their application to mechanical flexibility beyond conventional rigid structures, which have garnered new attention in the field of photoelectrochemical water splitting. A bendable metal (Hastelloy), which has both bendability and compatibility with various oxide layers, allows high-temperature processes for crystallization; therefore it is far superior as a substrate than a conventional flexible polymer. In this study, we fabricate bendable BiVO crystalline thin films on the metal substrates by employing template layers (SrRuO/SrTiO) to reduce the structural misfits between BiVO and the substrate. The crystallinities were verified through X-ray diffraction and transmission electron microscopy, and photocatalytic performances were examined. The crystallinity of BiVO was significantly improved by utilizing similar lattice constants and affinities between BiVO and the oxide template layers. We also formed a type II heterojunction by adding a WO layer which complements the charge separation and charge transfer as a photoanode. The photocurrent densities of tensile-bent BiVO/WO thin films with a bending radius of 10 mm are comparable to those of pristine BiVO/WO thin film in various aqueous electrolytes. Moreover, photostability tests showed that the tensile-bent crystalline photoanodes retained 90% of their initial photocurrent density after 24 h, which proved their exceptional durability. Our work demonstrates that the bendable photoelectrodes with crystallinity hold great potential in terms of device structure for solar-driven water splitting.