Boosted C-C coupling with Cu-Ag alloy sub-nanoclusters for CO 2 -to-C 2 H 4 photosynthesis.

The selective photocatalytic conversion of CO 2 and H 2 O to high value-added C 2 H 4 remains a great challenge, mainly attributed to the difficulties in C-C coupling of reaction intermediates and desorption of C 2 H 4 * intermediates from the catalyst surface. These two key issues can be simultaneously overcome by alloying Ag with Cu which gives enhanced activity to both reactions. Herein, we developed a facile stepwise photodeposition strategy to load Cu-Ag alloy sub-nanoclusters (ASNCs) on TiO 2 for CO 2 photoreduction to produce C 2 H 4 . The optimized catalyst exhibits a record-high C 2 H 4 formation rate (1110.6 ± 82.5 μmol g -1 h -1 ) with selectivity of 49.1 ± 1.9%, which is an order-of-magnitude enhancement relative to current work for C 2 H 4 photosynthesis. The in situ FT-IR spectra combined with DFT calculations reveal the synergistic effect of Cu and Ag in Cu-Ag ASNCs, which enable an excellent C-C coupling capability like Ag and promoted C 2 H 4 * desorption property like Cu, thus advancing the selective and efficient production of C 2 H 4 . The present work provides a deeper understanding on cluster chemistry and C-C coupling mechanism for CO 2 reduction on ASNCs and develops a feasible strategy for photoreduction CO 2 to C 2 fuels or industrial feedstocks.