Volume 3, 2025

Quantifying the prospect of a visible-light-absorbing oxysulfide photocatalyst by probing transient absorption and photoluminescence

Abstract

Photocatalytic water splitting is an emerging renewable technology for producing green hydrogen fuel from sunlight and water on a large scale. Identifying charge-carrier transport properties is critical for establishing a design pathway for exciting visible-light-absorbing oxysulfide-based photocatalysts. Herein, the dynamics of distinct charge carriers in the Gd2Ti2O5S2 (GTOS) photocatalyst is revealed by transient optical spectroscopies (transient diffuse reflectance (TDR) and transient photoluminescence (TPL) spectroscopies) and theoretical modeling. We demonstrate that TDR and TPL signals can probe the evolution of photoexcited mobile electrons and holes separately for GTOS. The decay of optical signals primarily originates from bimolecular recombination of mobile electrons with detrapped holes from shallow trap states close to the valence band. Using different estimated parameters, the effects of the size reduction and charge carrier extraction rate ke (surface to electrolyte) on the internal quantum efficiency (IQE) are determined. Our results indicate that the IQE can be tremendously improved by simultaneously reducing particle size and increasing ke. After particle size reduction, we show that the high apparent quantum yield (∼30%) GTOS was achieved by improving ke (from surface treatment and optimizing the cocatalyst loading method) as compared to Y2Ti2O5S2 (0.7%). Our work presents a comprehensive methodology that identifies the critical photophysical properties of visible-light-absorbing photocatalysts for efficient and scalable particulate photocatalyst-based solar water splitting systems.

Graphical abstract: Quantifying the prospect of a visible-light-absorbing oxysulfide photocatalyst by probing transient absorption and photoluminescence

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Article information

Article type
Paper
Submitted
05 Sep 2024
Accepted
11 Dec 2024
First published
27 Dec 2024
This article is Open Access
Creative Commons BY license

EES Catal., 2025,3, 274-285

Quantifying the prospect of a visible-light-absorbing oxysulfide photocatalyst by probing transient absorption and photoluminescence

R. Shoji, V. Nandal, K. Seki, X. Tao, A. Furube, T. Hisatomi, H. Yoshida, T. Takata, M. Kaneko, K. Yamashita, K. Domen and H. Matsuzaki, EES Catal., 2025, 3, 274 DOI: 10.1039/D4EY00187G

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