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

Abstract

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.

A Z‐Scheme Strategy that Utilizes ZnIn2S4 and Hierarchical VS2 Microflowers with Improved Charge‐Carrier Dynamics for Superior Photoelectrochemical Water Oxidation

“…[9,10] One heterojunction strategy that has received considerable attentioni s the Z-schemep hotocatalytic system. [11,12,[13][14][15][16] The advantage of the Z-scheme approach over conventionalt ype-II heterojunctions is that, apart from its improved separation of photogenerated chargec arriers,t he Z-schemes ystem also places electrons in am ore-negative conduction band (CB) and holes in a more-positive valenceb and (VB), which endows the photogenerated electrons and holes with stronger reductiona nd oxidation ability,r espectively. [17,18] At ypical Z-scheme photocatalytic system comprises two individual photocatalystsa nd as huttle redox mediator (or electron mediator), such as graphene, nanocarbon, or an oble metal (Au, Ag, etc.).…”

Photoelectrochemical study of carbon-modified p-type Cu2O nanoneedles and n-type TiO2−x nanorods for Z-scheme solar water splitting in a tandem cell configuration

“…88 Alternatively, a Z-scheme photocathode can be formed by depositing Cu 2 O on Auincorporated TiO 2 NRs array to improve the overall charge separation, the carrier density, and the kinetics of electron injection into electrolyte for enhancing the photoactivity toward solar-to-fuel energy conversion. 16 Another approach would be to combine TiO 2 NRs with chalcogenide to improve the aligned hole transport and charge-transfer kinetics. 89…”

“…8,9,12 In addition to requirements such as earth-abundance, stability, and low-cost; several approaches have been employed to develop active photocatalysts that can absorb solar energy in the entire UV-visible spectral region by including the use of heterojunction systems and nanostructure techniques. 10,[13][14][15][16] Inspired by nature's photosynthesis, a Zscheme solar water splitting system can be established that involves two different photoactive semiconductors, a p-and ntype material, via a two-step excitation mechanism to enhance charge carrier-separation and hence improve the overall photoconversion efficiency. 13,15,17 Fig.…”

Strong Light–Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting

“…Although one of the most successful semiconductors—for plasmonic PEC‐WS—is titanium dioxide (TiO 2 ), mainly owing to its chemical stability, earth abundance, and cost effectiveness; however, it suffers from a poor absorption response that only covers the ultraviolet (UV) portion of the solar spectrum. Therefore, in recent years, extensive attempts have been made for the design and realization of plasmonic coupled low band gap metal oxides for driving water oxidation and reduction reactions . By decorating plasmonic deep sub‐wavelength nanoparticles on a semiconductor, near field effects and hot electron injection can simultaneously contribute to the overall activity of the cell.…”