Insights into the charge transfer kinetics in BiVO4 photoanodes modified with transition metal-based oxygen evolution electrocatalysts

• Published in: Catalysis today 2023-03, Vol.413-415, p.113918, Article 113918
• Main Authors: Jahangir, Tahir Naveed, Khan, Abdul Zeeshan, Kandiel, Tarek A., El Ali, Bassam M.
• Format: Article
• Language: English
• Subjects: BiVO4; Charge Transfer kinetics; Fermi level pinning; IMPS; Layered double hydroxides (LDHs)
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2022.09.024

BiVO4 is a promising photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the sluggish water oxidation on its surface causes severe charge carriers recombination and thus reduces the overall efficiency. To overcome these imperfections, BiVO4 photoanodes were prepared and modified with transition metal-based oxygen evolution electrocatalysts, namely, NiFe, CoNi, and CoFe–layered double hydroxides (LDHs) oxygen evolution catalysts (OECs). The kinetics of charge transfer and recombination in the prepared photoanodes were studied by transient photocurrent and intensity-modulated photocurrent spectroscopy (IMPS). The rate constants of charge transfer and recombination were determined and correlated with the generated photocurrent to disclose the function of each electrocatalyst. It was concluded that the three investigated LDHs exhibit a comparable electrocatalytic activity at low applied potential, but CoNi–LDH has a superior passivation effect. Contrary to CoFe and NiFe–LDHs, CoNi–LDH passivates the surface states and unpins the Fermi level as proved by IMPS and photovoltage measurements. This study provides a systematic pathway to disclose the role of LDH OECs on BiVO4 surface which is an essential step for the rational design of efficient photoanodes. [Display omitted] •Pristine BiVO4 films were synthesized using Bi2O3 and vanadium precursors.•They were modified with transition metal-based layered double hydroxides (LDHs).•The lifetime and the rate constants of charge transfer and recombination were determined.•NiFe, CoNi, and CoFe–LDHs showed comparable electrocatalytic activity at low bias.•CoNi–LDH exhibits the highest passivation capability and unpins the Fermi level.