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 μmol·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.