Selectivity control for electrochemical CO2 reduction by charge redistribution on the surface of copper alloys

Vasileff, Anthony and Zhi, Xing and Xu, Chaochen and Ge, Lei ORCID: https://orcid.org/0000-0003-2989-0329 and Jiao, Yan and Zheng, Yao and Qiao, Shi-zhang (2019) Selectivity control for electrochemical CO2 reduction by charge redistribution on the surface of copper alloys. ACS Catalysis, 9 (10). pp. 9411-9417.


Abstract

Copper is a significant platform for CO2 electroreduction catalysts because it is the only known metal to produce multi-carbon products but suffers from poor selectivity. In the early stages of the reaction pathway, a selectivity-determining step dictates if the pathway leads to formate (a dead-end) or to CO (and on to multi-carbon products). Therefore, controlling the adsorption of key intermediates, in order to steer the reaction pathway as desired, is critical for selective CO2 electroreduction. Alloying copper is a strategy in which the composition and electronic properties of the alloy surface can be finely tuned to alter the reaction intermediate adsorption behavior. Herein, through in situ Raman spectroscopy and density functional theory (DFT) calculations, we investigate a composition-dependent selectivity toward CO and formate during CO2 electroreduction on a range of Cu–Sn alloy catalysts. We find that the selectivity shifts from CO to formate generation as the Sn content in the alloy catalyst increases because of a shift in adsorption preference from the C-bound *COOH intermediate to the O-bound *OCHO intermediate. Theoretical DFT calculation results indicate that this selectivity shift is due to a gradual weakening of *COOH adsorption and strengthening of *OCHO that occurs with increasing Sn content. A combination of theoretical Bader charge analysis and experimental X-ray photoelectron spectroscopy revealed the origin of such transformation: upon alloying, charge is redistributed from Sn to Cu, which creates regions of localized positive charge on the Sn sites. Therefore, with increasing tin content, these localized positive sites hinder the nucleophilic attack of the CO2 carbon, making *COOH adsorption (and the CO pathway) less favorable.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 09 Oct 2019 05:53
Last Modified: 20 Nov 2019 05:45
Uncontrolled Keywords: carbon dioxide reduction, copper alloys, selectivity control, Raman spectroscopy, density functional theory
Fields of Research : 03 Chemical Sciences > 0303 Macromolecular and Materials Chemistry > 030306 Synthesis of Materials
09 Engineering > 0904 Chemical Engineering > 090402 Catalytic Process Engineering
Socio-Economic Objective: B Economic Development > 86 Manufacturing > 8606 Industrial Chemicals and Related Products > 860601 Industrial Gases
Identification Number or DOI: 10.1021/acscatal.9b02312
URI: http://eprints.usq.edu.au/id/eprint/37124

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