Highly Efficient and Selective Photocatalytic Nonoxidative Coupling of Methane to Ethylene over Pd-Zn Synergistic Catalytic Sites.

Photocatalytic nonoxidative coupling of CH 4 to multicarbon (C 2+ ) hydrocarbons (e.g., C 2 H 4 ) and H 2 under ambient conditions provides a promising energy-conserving approach for utilization of carbon resource. However, as the methyl intermediates prefer to undergo self-coupling to produce ethane, it is a challenging task to control the selective conversion of CH 4 to higher value-added C 2 H 4 . Herein, we adopt a synergistic catalysis strategy by integrating Pd-Zn active sites on visible light-responsive defective WO 3 nanosheets for synergizing the adsorption, activation, and dehydrogenation processes in CH 4 to C 2 H 4 conversion. Benefiting from the synergy, our model catalyst achieves a remarkable C 2+ compounds yield of 31.85  μ mol·g -1 ·h -1 with an exceptionally high C 2 H 4 selectivity of 75.3% and a stoichiometric H 2 evolution. In situ spectroscopic studies reveal that the Zn sites promote the adsorption and activation of CH 4 molecules to generate methyl and methoxy intermediates with the assistance of lattice oxygen, while the Pd sites facilitate the dehydrogenation of methoxy to methylene radicals for producing C 2 H 4 and suppress overoxidation. This work demonstrates a strategy for designing efficient photocatalysts toward selective coupling of CH 4 to higher value-added chemicals and highlights the importance of synergistic active sites to the synergy of key steps in catalytic reactions.