Abstract
Copper-based bimetallic catalysts have been recently showing promising performance for the selective electrochemical reduction of CO2. In this work, we successfully fabricated the partially reduced oxides SnOx, CuOxmodified Cu foam electrode (A-Cu/SnO2) through an electrodeposition-annealing-electroreduction approach. Notably, in comparison with the control electrode (Cu/SnO2) without undergoing annealing step, A-Cu/SnO2 exhibits a significant enhancement in terms of CO2 reduction activity and CO selectivity. By investigating the effect of the amount of the electrodeposited SnO2, it is found that A-Cu/SnO2 electrodes present the characteristic Sn-Cu synergistic catalysis with a feature of dominant CO formation (CO faradaic efficiency, 70~75%), the least HCOOH formation (HCOOH faradaic efficiency, <5%) and the remarkable inhibition of hydrogen evolution reaction. In contrast, Cu/SnO2 electrodes exhibit a SnO2 coverage-dependent catalysis—a shift from CO selectivity to HCOOH selectivity with the increasing deposited SnO2 on Cu foam. The different catalytic performance between Cu/SnO2 and A-Cu/SnO2 might be attributed to the different content of Cu atoms in SnO2 layer, which may affect the density of Cu-Sn interface on the surface. Our work provides a facile annealing-electroreduction strategy to modify the surface composition for understanding the metal effect towards CO2 reduction activity and selectivity for bimetallic Cu-based electrocatalysts.
Highlights
Conversion of CO2 to valuable chemicals has been considered as a prospective way to reduce net CO2 emission and promote utilization of waste gas as well [1,2]
Electrochemical reduction of CO2 (ERC) is of particular interest, since with renewable electricity as an input, CO2 and water could be converted in a sustainable fashion into fuels and chemicals under mild conditions [3,4]
The Cu/SnO2 electrode was obtained by performing electrodeposition in the SnCl4 electrolyte for 30 min followed by the electroreduction treatment in a CO2 -saturated 0.1 M KHCO3 solution at −0.5 V vs. reversible hydrogen electrode (RHE) for an hour
Summary
Conversion of CO2 to valuable chemicals has been considered as a prospective way to reduce net CO2 emission and promote utilization of waste gas as well [1,2]. Electrochemical reduction of CO2 (ERC) is of particular interest, since with renewable electricity as an input, CO2 and water could be converted in a sustainable fashion into fuels and chemicals under mild conditions [3,4]. The viability of electrochemical conversion of carbon dioxide is currently restricted by the lack of inexpensive, efficient, selective and stable electrocatalysts. The majority of studies have focused on copper, aroused by a report from Hori and Suzuki that demonstrated methane and ethylene as the dominant products from CO2 reduction on a copper electrode. Experimental and theoretical studies have revealed that the selectivity of Cu can be tuned by introducing a secondary component, such as indium (In), tin (Sn) and sulfur (S) [11,12,13,14]
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