Rapid Screening of Photoanode Materials Using Scanning Photoelectrochemical Microscopy Technique and Formation of Z-Scheme Solar Water Splitting System by Coupling p- and n-type Heterojunction Photoelectrodes

A scanning photoelectrochemical microscopy (SPECM) technique is applied to rapidly screening the photoelectrochemical (PEC) activities of cobalt (Co)-incorporated bismuth vanadate (BiVO4) photocatalyst arrays with varying Co concentrations on conducting FTO and Ti substrates. The SPECM screening study is successfully utilized to determine an optimal Co concentration of 6% to improve the photocatalytic performance of BiVO4. Subsequently, pristine and Co-doped BiVO4 thin film photoanodes are fabricated by spin-coating/drop-casting methods with optimal precursor concentrations of Co, Bi, and V to validate the results of SPECM. Structural characterization by X-ray diffraction shows that 6% Co-BiVO4 contains a photocatalytically active scheelite-monoclinic phase of BiVO4. Scanning electron microscopy images and EDAX show that 6% Co is partly incorporated into the BiVO4 lattice and the remaining accumulates on the surface in the form of cobalt oxide, which is further evidenced by X-ray photoelectron spectroscop...