Effect of Cerium Precursors on Ce-Doped BiVO4 Nanoscale-Thick Films as Photoanodes: Implications for Water Splitting

Abstract

The use of the BiVO4 semiconductor to generate H2 via water splitting has recently been studied to meet the global energy demand. However, BiVO4 has some limitations such as higher electron-hole recombination and poor stability, being necessary studies that aim to give better performance. In this scenario, the use of the rare earths as a doping agent should be considered. This work explores the nanoscale-thick film BiVO4 electrochemical synthesis via BiOI film obtention and the effects of the use of different cerium precursors on the physical and photoelectrochemical (PEC) properties. Cerium(III) nitrate, cerium(IV) oxide, and ammonium cerium(IV) nitrate were evaluated as precursors and added into the plating solution before the electrochemical deposition. The films obtained underwent characterization through X-ray diffraction, SEM-EDS, and micro-Raman analyses. The results indicate that cerium is incorporated into the BiVO4 structure and that this incorporation did not alter its monoclinic structure, confirming the successful execution of the doping process. The PEC film characterization was evaluated by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy, showing a different PEC activity that depends on the used cerium precursors. The use of ammonium cerium(IV) nitrate improves the activity of the Ce-BiVO4 films, increasing the photocurrent by almost 2 times compared with pure BiVO4. Otherwise, the other precursors decrease the activity. Analysis of the ultraviolet-visible reflectance spectra and Mott-Schottky plots showed the difference between the material band gap and conduction band, highlighting that the use of different cerium precursors must be carefully evaluated to obtain a Ce-BiVO4 film with a lower electron-hole recombination. These achievements highlight the importance of understanding the effect of a cerium precursor on nanoscale-thick Ce-doped BiVO4 obtention for water-splitting applications as a photoanode.