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 (WO3) nanosheets to solve the poor conductivity issue while maintaining strong light absorption. The PEC activity of BBNO/WO3 nanosheet photoanodes can be further enhanced by applying Co0.8Mn0.2Ox 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/WO3 nanosheet photoanodes. The BBNO/WO3 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. To overcome the low electric conductivity of Ba2Bi1.4Nb0.6O6 (BBNO) while maintaining strong light absorption, ultrathin BBNO layers are coated onto aligned WO3 nanosheets. With the application of Co0.8Mn0.2Ox catalyst, the optically stacked but electrically parallel BBNO nanostructured photoelectrodes achieve photocurrent densities up to 6.02 mA cm−2 at 1.23 V (vs RHE) with excellent stability.