Analysis and characterization of BiVO4/FeOOH and BiVO4/α-Fe2O3 nanostructures photoanodes for photoelectrochemical water splitting

• Published in: Journal of materials science. Materials in electronics 2023-04, Vol.34 (11), p.1001, Article 1001
• Main Authors: Sánchez-Albores, R. M., Reyes-Vallejo, O., Ríos-Valdovinos, E., Fernández-Madrigal, A., Pola-Albores, F.
• Format: Article
• Language: English
• Subjects: Atoms & subatomic particles; Bismuth oxides; Carrier recombination; Characterization and Evaluation of Materials; Charge density; Charge transport; Chemistry and Materials Science; Current carriers; Efficiency; Electric contacts; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; Electromagnetic absorption; Energy; Energy gap; Ferric hydroxide; Ferric oxide; Materials Science; Optical and Electronic Materials; Oxidation; Oxygen evolution reactions; Photoanodes; Photoelectric effect; Photoelectric emission; Thin films; Vanadates; Water splitting
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-023-10382-1

In this work, BiVO 4 /FeOOH and BiVO 4 /Fe 2 O 3 electrodes were prepared by electrodeposition process and studied as a photoanode for water splitting application. Firstly, Iron (III) oxide–hydroxide (FeOOH) was deposited on BiVO 4 thin films, varying the deposit charge. Secondly, FeOOH was converted to Fe 2 O 3 by an annealing treatment at 500 °C in air. Structural, optical, morphological, and electrochemical characterization was performed by XRD, UV–Vis spectroscopy, FE-SEM, and electrochemical impedance. In both cases, the monoclinic phase of BiVO 4 was correctly coupled to each material. In all cases, a decrease in band gap was observed compared to pristine BiVO 4 which is indicative of an enhancement in photonic absorption, FE-SEM results revealed the coalescence of the BiVO 4 particles with particles in the form of nanosheets when FeOOH and Fe 2 O 3 were coupled. This increase in the rough surface is beneficial for the increase in reactive sites since it increases the semiconductor/electrolyte contact area in addition to increasing the photon-material interaction through multiple reflections provided by these 2D structures, thus improving charge transport. In the case of BiVO 4 /FeOOH, it is observed that as the deposit charge density (amount of electrical charge distributed per unit area) increases, there is an improvement in the photocurrent and less recombination effects due to the fact that no peaks are seen in the cathodic direction, which is characteristic of carrier recombination. The highest current density is observed in the BiVO 4 –FeOOH-250 mC sample with a value close to 0.20 mA/cm 2 . While BiVO 4 /Fe 2 O 3 films present higher photocurrents as the deposited charge increases reaching a value close to 0.35 mA/cm 2 , which is related to the increase in thickness and the decrease in the band gap, promoting greater light absorption. In addition, a correct band alignment for the oxygen evolution reaction was observed for both types of electrodes.