Photocatalytic nonoxidative coupling of methane to ethylene over carbon-doped ZnO/Au catalysts

A photocatalytic nonoxidative coupling of methane to multi-carbon compounds remains a huge challenge due to its high dissociation energy of C-H bonds and sluggish charge carrier dynamics. Au-modified carbon-doped ZnO (C-ZnO/Au) photocatalyst is constructed by an interfacial modification-assisted self-assembly approach for efficient photocatalytic nonoxidative coupling of methane to ethylene and hydrogen (2CH4 = C2H4 + 2H2). Benefitting from the presence of C-ZnO/Au interfaces, the catalyst not only weakens the excitonic confinement to improve the photogenerated charge carrier separation, but also enhances the stability of lattice oxygen to suppress C2H4 overoxidation. Moreover, this hybrid catalyst also accelerates the generation of Zn+-O- pairs to activate C-H bonds, stabilizes the important reaction intermediate (*OCH3) to achieve the C-C coupling, and promotes the generation of low-valence Zn to accelerate the dehydrogenation of the *OC2H5 into C2H4. Therefore, a stable photocatalytic methane conversion performance can be achieved over C-ZnO/Au heterojunctions with a stoichiometric generation of the oxidation product (C2H4, 45.85 & mu;mol g-1 h-1) and reduction product (H2, 88.07 & mu;mol g-1 h-1). This work provides deep insights into the elemental doping and oxide/Au interfaces for the enhanced photocatalytic activity and product selectivity under mild conditions in the absence of extra oxidants.