High Throughput Discovery of Effective Metal Doping in FeVO₄ for Photoelectrochemical Water Splitting

FeVO₄ is a potential photoanode candidate with favorable bandgap energy for absorbing visible light in the solar spectrum. However, the achieved photocurrents are still much lower than the theoretical photocurrent due to poor bulk carrier separation efficiency. Herein, the aim is to improve FeVO₄ charge transport properties by searching for suitable metal doping using combinatorial methods. Thin-film FeVO₄ libraries with different doping ratios of Zn, Ni, Cr, Mo, and W are fabricated on fluorine doped tin oxide substrates using combinatorial inkjet printing and their photoelectrochemical properties screened using photoscanning droplet cell. Mo and W doping show higher current density compared with undoped FeVO₄; whereas the photocurrent decreases for Ni- and Zn-doped samples. The best photocurrent is achieved with 7% doping ratio of Cr. Cr is discovered as a promising dopant for the first time, which is more effective than reported Mo or W for FeVO₄ photoanode. The replacement of Cr³⁺ to Fe³⁺ in FeVO₄ crystal lattice helps to mainly improve the catalytic activity for charge transfer, which results in the enhancement of photoresponse of the FeVO₄ photoanode.