Z-scheme water splitting utilizing CuLi 1/3 Ti 2/3 O 2 as a hydrogen-evolving photocatalyst with photo-response up to 600 nm

• Published in: Sustainable energy & fuels 2024-03, Vol.8 (6), p.1260-1268
• Main Authors: Yoshino, Shunya, Kurutach, Tanya, Liu, Qingshan, Yamanaka, Toshiki, Nozawa, Shunsuke, Kobayashi, Makoto, Kumagai, Hiromu, Kato, Hideki
• Format: Article
• Language: English
• ISSN: 2398-4902; 2398-4902
• DOI: 10.1039/D3SE01622F

CuLi 1/3 Ti 2/3 O 2 (CLTO) is a visible-responsive photocatalyst, whose photo-response reaches up to 600 nm, for H 2 evolution using sacrificial electron donors such as methanol and S 2− . In this study, utilization of CLTO in Z-scheme water splitting (Z-WS) was investigated. The photocatalytic performance of Cr 2 O 3 /M/CLTO as a H 2 -evolving photocatalyst, which was prepared by sequential photodeposition of cocatalysts (M: Ru, Rh, Pd and Pt) and Cr 2 O 3 , was evaluated for Z-WS using BiVO 4 , an O 2 -evolving photocatalyst, and a Co(bpy) 3 3+/2+ redox shuttle under visible light. Among the examined samples, Cr 2 O 3 /Ru/CLTO produced both H 2 and O 2 with meaningful rates. Thus, CLTO was first utilized in a visible responsive Z-scheme system for water splitting. The Cr 2 O 3 layer played a significant role in the suppression of backward reactions, such as reduction of Co(bpy) 3 3+ . The activity of Cr 2 O 3 /Ru/CLTO for Z-WS was remarkably affected by the deposition conditions of the Ru cocatalyst. The activity for Z-WS was remarkably improved when the photodeposition of the Ru cocatalyst was conducted in a methanol solution of RuCl 3 . Unusually large plate Ru species with 100–200 nm sizes and about 30 nm thickness were present in the highly active sample. Characterization using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy indicated that the Ru cocatalyst was deposited as mainly the oxyhydroxide of Ru. Z-WS also proceeded in the absence of Co(bpy) 3 3+/2+ (the system based on interparticle electron transfer), however, the Z-scheme system using the Co(bpy) 3 3+/2+ electron shuttle showed 10 times higher activity than the interparticle electron transfer system. The external quantum yield and efficiency of solar energy conversion to hydrogen were determined to be 0.5% at 430 nm and 0.029%, respectively.