Enhanced Ethylene Formation from Carbon Dioxide Reduction through Sequential Catalysis on Au Decorated Cubic Cu2O Electrocatalyst

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 Cu2O electrocatalysts were synthesized via the galvanic replacement reaction and the successive pre-reduction by linear voltammetry (LSV) method. In contrast to Cu2O, CO formation became dominant over HCOOH and H-2 on AuxCu2O, and a remarkably enhanced selectivity of C2H4 was obtained beyond -1.1 V vs. RHE. Among them, Au0.02Cu2O exhibited the highest Faraday efficiency (FE) of C2H4 of 24.4 % at -1.3 V vs. RHE, which was as high as 2 similar to 2.5 and 5 times of those on other two AuxCu2O and bare Cu2O, respectively. Meanwhile, it is demonstrated that the optimal ratio of Au/Cu was essential for effective sequential catalysis between Au and Cu2O to enhance C-C coupling. Furthermore, the effect of copper states resulting from different pre-reduction methods on the selectivity of C2H4 was explored. A half decrease of C2H4 FE was observed on HPR-Au0.02Cu2O (high potential reduced) relative to the LSV reduced Au0.02Cu2O, which was ascribed to the different content of Cu-0 and residual Cu+ in two catalysts. Our results demonstrate an effective approach to construct Cu2O based bimetallic catalysts for ethylene formation from CO2.