Binary Au–Cu Reaction Sites Decorated ZnO for Selective Methane Oxidation to C1 Oxygenates with Nearly 100% Selectivity at Room Temperature

Abstract

Direct and efficient oxidation of methane to methanol and the related liquid oxygenates provides a promising pathway for sustainable chemical industry, while still remaining an ongoing challenge owing to the dilemma between methane activation and overoxidation. Here, ZnO with highly dispersed dual Au and Cu species as cocatalysts enables efficient and selective photocatalytic conversion of methane to methanol and one-carbon (C1) oxygenates using O 2 as the oxidant operated at ambient temperature. The optimized AuCu−ZnO photocatalyst achieves up to 11225 μmol•g −1 •h −1 of primary products (CH 3 OH and CH 3 OOH) and HCHO with a nearly 100% selectivity, resulting in a 14.1% apparent quantum yield at 365 nm, much higher than the previous best photocatalysts reported for methane conversion to oxygenates. In situ EPR and XPS disclose that Cu species serve as photoinduced electron mediators to promote O 2 activation to • OOH, and simultaneously that Au is an efficient hole acceptor to enhance H 2 O oxidation to • OH, thus synergistically promoting charge separation and methane transformation. This work highlights the significances of co-modification with suitable dual cocatalysts on simultaneous regulation of activity and selectivity.

Synergy of Pd atoms and oxygen vacancies on In2O3 for methane conversion under visible light

“…Photocatalysis offers an appealing alternative to drive many tough redox reactions under mild conditions including CO 2 conversion 18 , 19 , N 2 reduction 20 and selective CH 4 oxidation 8 . Recently, various value-added chemicals such as methanol 1 , 21 – 24 , formaldehyde 25 , 26 , ethanol 27 , 28 , ethane and ethylene 29 – 34 were produced by photocatalysis. For example, we found that up to 90% selectivity with a yield of 3.5 μmol h −1 methanol could be achieved over the optimized FeO x /TiO 2 photocatalyst under ambient condition using H 2 O 2 as an oxidant 22 .…”

Selective Photocatalytic Oxidation of Methane to Oxygenates over Cu–W–TiO2 with Significant Carrier Traps

“…For example, an oxygenate productivity of 12500 μmol g –1 h –1 with a selectivity of 95% was obtained for a 0.1 wt % Au/ZnO catalyst in the presence of O 2 under a light irradiation of 300–500 nm . 11225 μmol g –1 h –1 C1 oxygenates could be produced over a AuCu–ZnO catalyst using O 2 as an oxidant at ambient temperature . Ag-decorated TiO 2 catalyzed direct methane oxidation to oxygenated products with the productivity and selectivity reaching 5400 μmol g –1 h –1 and 90%, respectively .…”

Quantifying Hot Electron Energy Contributions in Plasmonic Photocatalysis Using Electrochemical Surface-Enhanced Raman Spectroscopy

“…Hot (energetic) electrons produced by nonradiative decay of surface plasmons − are a highly promising energy source for chemical reactions because they can reduce the activation barrier by exciting the adsorbed molecules. , For example, the plasmon-mediated process is able to drive water splitting, − H 2 dissociation, − O 2 dissociation, , N 2 fixation, − and synthesis of commercially important chemicals , under mild conditions. However, little is known about the energy contribution of hot electrons in these chemical reactions.…”