Effect of Cerium Precursors on Ce-Doped BiVO<sub>4</sub> Nanoscale-Thick Films as Photoanodes: Implications for Water Splitting
Matheus G. Guardiano, Lara Kelly Ribeiro, Isabelle M.D. Gonzaga, Lúcia H. Mascaro
Abstract
High Resolution Image Download MS PowerPoint Slide The use of the BiVO 4 semiconductor to generate H 2 via water splitting has recently been studied to meet the global energy demand. However, BiVO 4 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 BiVO 4 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 BiVO 4 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–BiVO 4 films, increasing the photocurrent by almost 2 times compared with pure BiVO 4 . 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–BiVO 4 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 BiVO 4 obtention for water-splitting applications as a photoanode.