Tuning Sn-Cu Catalysis for Electrochemical Reduction of CO₂ on Partially Reduced Oxides SnOx-CuOx-Modified Cu Electrodes

• Main Authors: Qianwen Li, Mei Li, Shengbo Zhang, Xiao Liu, Xinli Zhu, Qingfeng Ge, Hua Wang
• Format: Article
• Language: English
• Published: MDPI AG 2019-05-01
• Series: Catalysts
• Subjects: electrochemical reduction of CO₂; tin oxide-modified copper electrode; electrodeposition; annealing treatment
• Online Access: https://www.mdpi.com/2073-4344/9/5/476

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, CuOx modified 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.