Electrochemical reduction of carbon dioxide to fuels has been recognized as a perspective way to address the environmental and energy issues. Herein, the novel Au decorated Cu 2 O electrocatalysts were synthesized via the galvanic replacement reaction and the successive pre-reduction by linear voltammetry (LSV) method. In contrast to Cu 2 O, CO formation became dominant over HCOOH and H 2 on Au x Cu 2 O, and a remarkably enhanced selectivity of C 2 H 4 was obtained beyond À 1.1 V vs. RHE. Among them, Au 0.02 Cu 2 O exhibited the highest Faraday efficiency (FE) of C 2 H 4 of 24.4 % at À 1.3 V vs. RHE, which was as high as 2~2.5 and 5 times of those on other two Au x Cu 2 O and bare Cu 2 O, respectively. Meanwhile, it is demonstrated that the optimal ratio of Au/Cu was essential for effective sequential catalysis between Au and Cu 2 O to enhance CÀ C coupling. Furthermore, the effect of copper states resulting from different pre-reduction methods on the selectivity of C 2 H 4 was explored. A half decrease of C 2 H 4 FE was observed on HPR-Au 0.02 Cu 2 O (high potential reduced) relative to the LSV reduced Au 0.02 Cu 2 O, which was ascribed to the different content of Cu 0 and residual Cu + in two catalysts. Our results demonstrate an effective approach to construct Cu 2 O based bimetallic catalysts for ethylene formation from CO 2 .

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