TiO2‑Au-Cu2O Photocathodes: Au-Mediated Z‑Scheme Charge Transfer for Efficient Solar-Driven Photoelectrochemical Reduction

• Published in: ACS applied nano materials Vol. 1; no. 12; pp. 6843 - 6853
• Main Authors: Li, Jing-Mei, Tsao, Chun-Wen, Fang, Mei-Jing, Chen, Chun-Chi, Liu, Chen-Wei, Hsu, Yung-Jung
• Format: Journal Article
• Language: English
• Published: American Chemical Society 28.12.2018
• Subjects: Au-mediated; Z-scheme; photocathode; photoelectrochemical reduction; Cu2O
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.8b01678

An Au-mediated Cu2O-based Z-scheme heterostructure system is demonstrated for use as efficient photocathodes in photoelectrochemical (PEC) reduction. The samples are prepared by electrodepositing a Cu2O layer on the surface of Au particle-coated TiO2 nanorods. For TiO2-Au-Cu2O, the embedded Au particles function as a charge transfer mediator to enhance the electron transportation from the conduction band of TiO2 to the valence band of Cu2O. Such a vectorial charge transfer leads to the concentration of electrons at the conduction band of Cu2O and the collection of holes at the valence band of TiO2, providing TiO2-Au-Cu2O with substantially high redox abilities for reduction applications. Time-resolved photoluminescence spectra and electrochemical impedance spectroscopy analysis suggest that interfacial charge transfer is significantly improved because of the Au-mediated Z-scheme charge transfer mechanism. By virtue of the high redox ability and improved interfacial charge transfer, TiO2-Au-Cu2O performs much better as a photocathode in H2 production and CO2 reduction than pure Cu2O and binary TiO2-supported Cu2O do. Remarkably, the photocurrent density of TiO2-Au-Cu2O toward PEC CO2 reduction can reach as high as −1.82 mA/cm2 at +0.11 V vs RHE. The incident photon-to-current conversion efficiency data manifest that TiO2-Au-Cu2O surpasses both pure Cu2O and binary TiO2-supported Cu2O in PEC reduction across the whole photoactive region. The current study paves a valuable approach of devising Z-scheme photocathode for the construction of sophisticated artificial photosynthesis systems capable of solar-to-fuel conversion.