Issue 8, 2024

Expediting hole transfer kinetics through surface state modulation of a Ru–FeOOH and FeNi(OH)x dual-layer cocatalyst coated Zr–Fe2O3 photoanode for boosting photoelectrochemical water splitting

Abstract

The potential of a hematite photoanode for photoelectrochemical (PEC) water oxidation is primarily constrained by its sluggish water oxidation kinetics due to severe charge recombination at recombination surface states (r-SS). Abundant r-SS are responsible for a Fermi level pinning effect, which causes a potential drop in the Helmholtz layer. Tuning surface states is crucial for improving charge transfer at the semiconductor–electrolyte interface (SEI). In this context, cocatalyst loading is a potential strategy for promoting charge transfer by modulating intermediate surface states (i-SS). Accordingly, Ru-incorporated FeOOH and microwave-assisted FeNi(OH)x dual-layer cocatalysts (DLCs) were coated on a Zr-doped Fe2O3 photoanode to investigate surface charge transfer kinetics at the SEI. The optimized Zr-HT/Ru–FeOOH/FNH photoelectrode achieved a photocurrent density of 2.27 mA cm−2 with a surface charge separation efficiency of 96.6% at 1.23 V vs. RHE. The DLC modulated the i-SS and facilitated hole transfer, leading to Fermi level de-pinning through passivation of r-SS. Moreover, cocatalyst loading increased the surface-active area, which enhanced the number of active sites available for charge transfer reactions. During PEC water splitting, the optimized Zr-HT/Ru–FeOOH/FNH photoanode generated 38.2 and 18.5 μmol h−1 of H2 and O2 gases, respectively. The approach of using dual-layer cocatalysts provides a new technique for stimulating and advancing the effectiveness of metal oxide photoanodes by tailoring surface states for PEC water oxidation.

Graphical abstract: Expediting hole transfer kinetics through surface state modulation of a Ru–FeOOH and FeNi(OH)x dual-layer cocatalyst coated Zr–Fe2O3 photoanode for boosting photoelectrochemical water splitting

Supplementary files

Article information

Article type
Paper
Submitted
18 Dec 2023
Accepted
14 Jan 2024
First published
25 Jan 2024

J. Mater. Chem. A, 2024,12, 4702-4711

Expediting hole transfer kinetics through surface state modulation of a Ru–FeOOH and FeNi(OH)x dual-layer cocatalyst coated Zr–Fe2O3 photoanode for boosting photoelectrochemical water splitting

P. Anushkkaran, W. Chae, J. Ryu, S. H. Choi and J. S. Jang, J. Mater. Chem. A, 2024, 12, 4702 DOI: 10.1039/D3TA07823J

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