Electrolytic Methane Production from Reactive Carbon Solutions

Abstract

We report an electrochemical reactor that converts 3.0 M KHCO3 into methane at the cathode, and oxidizes water at the anode. The molar ratio of methane product to unreacted CO2 gas (defined herein as “methane yield”) was measured to be 34% at a partial current density of 120 mA cm–2. The highest previously reported CO2-to-methane yield is 3%. Our reactor achieved this improvement in methane yield because it is fed with 3.0 M KHCO3, a type of reactive carbon solution, rather than gaseous CO2. The reactor uses H+ delivered by a bipolar membrane to form CO2 at the cathode. This CO2 is subsequently reduced into methane. A cationic surfactant added to the catholyte suppressed hydrogen evolution and increased methane formation. A 1D continuum model confirmed that H+ from the membrane promotes the formation of methane over multicarbon products at the cathode. These findings present design principles for electrochemical methane synthesis.

Carbonation in Low-Temperature CO2 Electrolyzers: Causes, Consequences, and Solutions

“…A high CD (>300 mA/cm 2 ) and a low flow rate were more beneficial for the downstream process, since the formate product stream was more concentrated, but at an expense of a lower energy efficiency. Lees et al 91 used a BPM-based flow cell and a Cu cathode to convert bicarbonate (3 M KHCO 3 ) to methane. By adding a cationic surfactant to the catholyte that suppressed the HER, these authors obtained an FE of 27% and a yield of 34% for methane at a CD of 400 mA/cm 2 and cell voltage of 7.2 V. Recently, Zhang et al 92 used a CEM-based flow cell coupled with the hydrogen oxidation reaction (HOR) at the anode to convert a 3 M KHCO 3 solution into CO.…”

Bicarbonate Electroreduction to Multicarbon Products Enabled by Cu/Ag Bilayer Electrodes and Tailored Microenviroments

“…For instance, Berlinguette and co-workers reported faradaic efficiency (FE) of > 60 % toward CO and formate at the current densities of > 100 mA cm À 2 , [7] and the FE of 34 % toward CH 4 at a partial current density of 120 mA cm À 2 . [8] Despite significant research progress in C 1 product generation, multicarbon (C 2 + ) (i. e., acetate, ethylene, ethanol, propanol) as the major products were rarely reported in the bicarbonate-based system.…”

MOF-Derived Ni Single-Atom Catalyst with Abundant Mesopores for Efficient Mass Transport in Electrolytic Bicarbonate Conversion

“…The electrolytic CO 2 reduction reaction (CO 2 RR) offers a promising route to convert CO 2 to fuels or value-added chemicals. − However, conventional CO 2 electrolysis employs high-purity CO 2 as the feedstock, which requires a considerable amount of energy input during the processes of CO 2 capture and separation. Typically, the energy requirements during CO 2 capture and separation account for >76% in a traditional postcombustion CO 2 capture system .…”