Title: Electrochemical Carbon Monoxide Reduction on Polycrystalline Copper: Effects of Potential, Pressure, and pH on Selectivity toward Multicarbon and Oxygenated Products

Abstract

Here by understanding the surface reactivity of CO, which is a key intermediate during electrochemical CO₂ reduction, is crucial for the development of catalysts that selectively target desired products for the conversion of CO₂ to fuels and chemicals. In this study, a custom-designed electrochemical cell is utilized to investigate planar polycrystalline copper as an electrocatalyst for CO reduction under alkaline conditions. Seven major CO reduction products have been observed including various hydrocarbons and oxygenates which are also common CO₂ reduction products, strongly indicating that CO is a key reaction intermediate for these further-reduced products. A comparison of CO and CO₂ reduction demonstrates that there is a large decrease in the overpotential for C–C coupled products under CO reduction conditions. The effects of CO partial pressure and electrolyte pH are investigated; we conclude that the aforementioned large potential shift is primarily a pH effect. Thus, alkaline conditions can be used to increase the energy efficiency of CO and CO₂ reduction to C–C coupled products, when these cathode reactions are coupled to the oxygen evolution reaction at the anode. Further analysis of the reaction products reveals common trends in selectivity that indicate both the production of oxygenates and C–C coupled products aremore » favored at lower overpotentials. These selectivity trends are generalized by comparing the results on planar Cu to current state-of-the-art high-surface-area Cu catalysts, which are able to achieve high oxygenate selectivity by operating at the same geometric current density at lower overpotentials. Combined, these findings outline key principles for designing CO and CO₂ electrolyzers that are able to produce valuable C–C coupled products with high energy efficiency.« less

Authors:

Wang, Lei ^[1]; Nitopi, Stephanie A. ^[1]; Bertheussen, Erlend ^[2]; Orazov, Marat ^[1]; Morales-Guio, Carlos G.  ^[1];

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Liu, Xinyan ^[1]; Higgins, Drew C.  ^[3];

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Chan, Karen  ^[3];

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Nørskov, Jens K. ^[3]; Hahn, Christopher  ^[3];

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Jaramillo, Thomas F.  ^[3]

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+ Show Author Affiliations

1. Stanford Univ., Stanford, CA (United States)
2. Technical Univ. of Denmark, Lyngby (Denmark)
3. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

Publication Date:

2018-07-18

Research Org.:

SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1469211

Grant/Contract Number:  

SC0004993; AC02-76SF00515

Resource Type:

Accepted Manuscript

Journal Name:

ACS Catalysis

Additional Journal Information:

Journal Volume: 8; Journal Issue: 8; Related Information: The Supporting Information is available free of charge on the ACS Publications website at https://pubs.acs.org/doi/suppl/10.1021/acscatal.8b01200; Journal ID: ISSN 2155-5435

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; carbon monoxide; carbon monoxide reduction; copper; overpotential; pH effect; selectivity