Barium Bismuth Niobate Double Perovskite/Tungsten Oxide Nanosheet Photoanode for High‐Performance Photoelectrochemical Water Splitting

Recently, a new method to effectively engineer the bandgap of barium bismuth niobate (BBNO) double perovskite was reported. However, the planar electrodes based on BBNO thin films show low photocurrent densities for water oxidation owing to their poor electrical conductivity. Here, it is reported that the photoelectrochemical (PEC) activity of BBNO‐based electrodes can be dramatically enhanced by coating thin BBNO layers on tungsten oxide (WO 3 ) nanosheets to solve the poor conductivity issue while maintaining strong light absorption. The PEC activity of BBNO/WO 3 nanosheet photoanodes can be further enhanced by applying Co 0.8 Mn 0.2 O x nanoparticles as a co‐catalyst. A photocurrent density of 6.02 mA cm −2 at 1.23 V (vs reversible hydrogen electrode (RHE)) is obtained using three optically stacked, but electrically parallel, BBNO/WO 3 nanosheet photoanodes. The BBNO/WO 3 nanosheet photoanodes also exhibit excellent stability in a high‐pH alkaline solution; the photoanodes demonstrate negligible photocurrent density decay while under continuous PEC operation for more than 7 h. This work suggests a viable approach to improve the PEC performance of BBNO absorber‐based devices.