Enhanced Hydrogen Production from Ethanol Photoreforming by Site-Specific Deposition of Au on Cu2O/TiO2 p-n Junction

Abstract

Hydrogen production by photoreforming of biomass-derived ethanol is a renewable way of obtaining clean fuel. We developed a site-specific deposition strategy to construct supported Au catalysts by rationally constructing Ti3+ defects inTiO2 nanorods and Cu2O-TiO2 p-n junction across the interface of two components. The Au nanoparticles (~2.5 nm) were selectively anchored onto either TiO2 nanorods (Au@TiO2/Cu2O) or Cu2O nanocubes (Au@Cu2O/TiO2) or both TiO2 and Cu2O (Au@TiO2/Cu2O@Au) with the same Au loading. The electronic structure of supported Au species was changed by forming Au@TiO2 interface due to the adjacent Ti3+ defects and the associated oxygen vacancies while unchanged in Au@Cu2O/TiO2 catalyst. The p-n junction of TiO2/Cu2O promoted charge separation and transfer across the junction. During ethanol photoreforming, Au@TiO2/Cu2O catalyst possessing both the Au@TiO2 interface and the p-n junction showed the highest H2 production rate of 8548 μmol gcat−1 h−1 under simulated solar light, apparently superior to both Au@TiO2 and Au@Cu2O/TiO2 catalyst. The acetaldehyde was produced in liquid phase at an almost stoichiometric rate, and C−C cleavage of ethanol molecules to form CH4 or CO2 was greatly inhibited. Extensive spectroscopic results support the claim that Au adjacent to surface Ti3+ defects could be active sites for H2 production and p-n junction of TiO2/Cu2O facilitates photo-generated charge transfer and further dehydrogenation of ethanol to acetaldehyde during the photoreforming.

Dual promotional effect of CuxO clusters grown with atomic layer deposition on TiO2 for photocatalytic hydrogen production

“…It also agrees with the previous observations, suggesting the significant contribution of Ti 3+ to photocatalytic activity of CuxO/TiO2 catalysts [53,57]. The Ti 3+ species are produced due to the transfer of photo-excited electrons of CuxO clusters to TiO2 [59], and the increase of Ti 3+ content in CuxO/TiO2 samples indicates the expansion of the depletion zone on the photocatalyst. It can be inferred that the depletion zone around the cocatalyst particles is the photocatalytically active area, and its growth increases the photocatalyst activity.…”

Photocatalytic hydrogen evolution from biomass conversion

“…The complete photo-reformation of ethanol into hydrogen and carbon dioxide gas proceeds with hydrogen gas first formed in the reaction sequence following dehydrogenation to give acetaldehyde [ 88 ]. Carbon dioxide subsequently forms during the proceeding oxidation steps.…”

Supported Plasmonic Nanocatalysts for Hydrogen Production by Wet and Dry Photoreforming of Biomass and Biogas Derived Compounds: Recent Progress and Future Perspectives

“…Other studies were devoted to even more complex systems with a hierarchical structure. Luo et al [74] . reported the synthesis of Cu 2 O/TiO 2 p‐n junction with site‐specific deposited Au.…”