Direct Liquid Injection Chemical Vapor Deposition of Molybdenum Doped Bismuth Vanadate Photoelectrodes for Efficient Solar Water Splitting

The direct liquid injection chemical vapor deposition (DLI-CVD) method is used to grow pristine and molybdenum (Mo)-doped monoclinic scheelite phase bismuth vanadate (BVO) photoelectrodes. Superior photoelectrochemical (PEC) performance is achieved with similar to 200 +/- 50 nm thick pristine and 8 at. % Mo-doped BVO films grown at 550 degrees C. Photo current densities as high as similar to 1.65 and 3.25 mA/cm(2) are obtained for pristine and optimum 8% Mo-doped BVO electrodes, respectively, at 1.23 V vs reversible hydrogen electrode (RHE) under visible light AM 1.5G (100 mW/cm(2)) in 0.5 M phosphate buffer electrolyte in the presence of 0.1 M (NaSO3)-S-2 hole scavenger. Somewhat lower photocurrent densities of similar to 1.5 and 2.4 mA/cm(2) are obtained for pristine and optimum 8% Mo-doped BVO electrodes, respectively, in the absence of Na2SO3. Onset potential values as low as similar to OA and 0.3 V vs RHE are achieved with pristine and Mo-doped BVO films for sulfite and water oxidation, respectively. The increased photocurrent density with Mo doping is attributed to enhanced charge carrier density and film conductivity as confirmed by PEC and Mott-Schottky analyses. Because of the dense high quality polycrystalline structure, the DLI-CVD fabricated Mo-doped BVO electrodes exhibit substantial stability under water and sulfite oxidation conditions without any protective layer and/or oxygen evolution cocatalysts. Scanning electrochemical microscopy (SECM) studies confirm the low porosity of Mo:BVO films and production of oxygen in a local area of Mo:BVO electrode under light illumination.