Syngas (CO + H 2 ) is the incredibly important feedstock for producing synthetic fuels and various value-added chemicals. CO 2 electrochemical reduction to syngas is an environmental-friendly and sustainable approach, but still challenging to produce tunable syngas with a wide ratio of CO/H 2 . Herein, by modulating the structure and phase, we have successfully obtained a series of copper-indium (Cu-In) catalysts, which are efficient for producing syngas with tunable CO/H 2 ratios. A series of CuIn bimetallic catalysts with different structures from hollow sphere to two-layer hollow sphere and different phases from CuO to Cu 2 O are developed. We find that the CO and H 2 are the only gaseous products, in which the CO/H 2 ratios can be readily tuned from 1.2 ± 0.1 to 9.0 ± 1.5 by simply controlling the thermal annealing temperature. It also exhibits high durability during a 10-h test. The unique performance is attributed to the modulated In enrichment on the Cu surfaces during the CO 2 reduction reaction, which causes the differences in binding energies for key reaction intermediates, thus resulting in the tunable composition of syngas. The present work emphasizes a simple yet efficient phase and structure modulating strategy for designing potential electrocatalysts for producing syngas with widely tunable CO/H 2 ratios.
This work reports a novel and effective method for the preparation of the copper-indium bimetallic electrocatalysts by the in situ growth of indium-based metal organic frameworks on oxidized copper foils as the precursor. Compared with the oxide-derived copper and the copper-based carbon material derivative grown in situ on oxidized copper foils, the as-prepared copper-indium electrocatalyst with a self-supporting structure, high roughness factor and rich lattice defects exhibits a superior CO Faradaic efficiency of 95% and good stability for the 36-h potentiostatic test at −0.6 V versus a reversible hydrogen electrode. Density functional theory calculations indicated that the indium atoms occupying the surface copper vacancy defects show lower free energy needed for the formation of *COOH and more difficult desorption of *H than indium atoms, supported on the perfect copper surface. Thereby, the copper-indium catalyst promotes CO 2 electroreduction to CO and strongly inhibits hydrogen evolution.
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