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

Lei Wang, Stephanie A. Nitopi, Erlend Bertheussen, Marat Orazov, Carlos G. Morales-Guio, Xinyan Liu, Drew C. Higgins, Karen Chan, Jens K. Nørskov, Christopher Hahn, Thomas F. Jaramillo*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Understandingthe surface reactivity of CO, which is a key intermediateduring electrochemical CO2 reduction, is crucial for thedevelopment of catalysts that selectively target desired productsfor the conversion of CO2 to fuels and chemicals. In thisstudy, a custom-designed electrochemical cell is utilized to investigateplanar polycrystalline copper as an electrocatalyst for CO reductionunder alkaline conditions. Seven major CO reduction products havebeen observed including various hydrocarbons and oxygenates whichare also common CO2 reduction products, strongly indicatingthat CO is a key reaction intermediate for these further-reduced products.A comparison of CO and CO2 reduction demonstrates thatthere is a large decrease in the overpotential for C–C coupledproducts under CO reduction conditions. The effects of CO partialpressure and electrolyte pH are investigated; we conclude that theaforementioned large potential shift is primarily a pH effect. Thus,alkaline conditions can be used to increase the energy efficiencyof CO and CO2 reduction to C–C coupled products,when these cathode reactions are coupled to the oxygen evolution reactionat the anode. Further analysis of the reaction products reveals commontrends in selectivity that indicate both the production of oxygenatesand C–C coupled products are favored at lower overpotentials.These selectivity trends are generalized by comparing the resultson planar Cu to current state-of-the-art high-surface-area Cu catalysts,which are able to achieve high oxygenate selectivity by operatingat 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–Ccoupled products with high energy efficiency.
Original languageEnglish
JournalA C S Catalysis
Volume8
Pages (from-to)7445-7454
ISSN2155-5435
DOIs
Publication statusPublished - 2018

Keywords

  • Carbon monoxide reduction
  • Copper
  • Selectivity
  • Carbon monoxide
  • H effect
  • Overpotential

Cite this