Issue 8, 2023

Role of defect density in the TiOx protective layer of the n-Si photoanode for efficient photoelectrochemical water splitting

Abstract

Photocorrosion of the anode participating in photo-electrochemical (PEC) water splitting is one of the obstacles for long-term stability. To prevent photocorrosion, an “electrically leaky” thick TiO2 film was deposited onto an n-Si photoanode surface. However, the carrier transport mechanism through the thick dielectric layer and the interface between the dielectric layer and n-Si is still unclear. In order to explore the carrier transport mechanism, we only modulated the defect density of the protective TiOx(1.98≤x≤2.0) film with no significant change in optical and physical properties, and chemical composition. The fact that the defect density of the TiOx film is proportional to water-splitting activity allows us to explain the hole transport mechanism of the previously reported electrically leaky TiO2 protection layer in the n-Si photoanode. For the defect-level optimization, controlled incorporation of defects into TiOx(1.94≤x≤2.0) dramatically enhances the hole transport from the photoanode surface to the electrolyte solution. The influence of the protection layer defect density on the band structure and water-splitting activity of the photoanode system was explored. Mott–Schottky analysis of this system suggests that the defect level of the TiOx films influences the band bending of n-Si, which governs the accessible density of defect states and the carrier recombination. Our photoanode consisting of the 50 nm-thick TiOx protection layer with the optimal defect density retained about 85% of the initial current density after 100 h of PEC reaction.

Graphical abstract: Role of defect density in the TiOx protective layer of the n-Si photoanode for efficient photoelectrochemical water splitting

Supplementary files

Article information

Article type
Paper
Submitted
08 Sep 2022
Accepted
12 Jan 2023
First published
13 Jan 2023

J. Mater. Chem. A, 2023,11, 3987-3999

Role of defect density in the TiOx protective layer of the n-Si photoanode for efficient photoelectrochemical water splitting

S. Hong, W. Lee, Y. J. Hwang, S. Song, S. Choi, H. Rhu, J. H. Shim and A. Kim, J. Mater. Chem. A, 2023, 11, 3987 DOI: 10.1039/D2TA07082K

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