Selective Reduction of CO2 to Methane
Luca, O. R., McCrory, C. C. L., Dalleska, N. F. & Koval, C. A. The Selective Electrochemical Conversion of Preactivated CO2 to Methane. Journal of The Electrochemical Society, 162(7), H473-476, DOI: 10.1149/2.0371507jes (2015).
Demonstration of selective electrochemical reduction of CO2 to methane with Faradaic efficiency as high as 93%.
Significance & impact
CO2 is preactivated with an N-heterocyclic carbene, and in the presence of reducing potential and a Ni(cyclam)2+ mediator yields a 8e−/8H+ selective reduction reaction to methane.
13C Labeling experiments for the reduction of NHC-CO2-13C. Top: Chemical equation for the 13C-labeling experiment in the selective electrochemical conversion of CO2 to methane. Bottom: Water-resolved mass spectrum of an electrolysis headspace sample for the 13C-labeling experiment.
- To facilitate CO2RR selectivity, the CO2 was converted into zwitterionic NHC-CO2 carboxylate, and was reduced in the presence of a Ni mediator in a protic medium.
- Controlled potential electrolysis combined with headspace analyses by GC-TCD and GC-MS was used to confirm the identity and the source of electrolysis products.
- The 13C labeling experiments confirm that the source of carbon in electrochemically produced methane is from NHC-13CO2.