Electrolytic Methane Production fromReactive Carbon Solutions

We report an electrochemical reactor that converts 3.0 M KHCO3into methane at the cathode, and oxidizes water at the anode. The molar ratio ofmethane product to unreacted CO2gas (defined herein asmethane yield) wasmeasured to be 34% at a partial current density of 120 mA cm-2. The highestpreviously reported CO2-to-methane yield is 3%. Our reactor achieved thisimprovement in methane yield because it is fed with 3.0 M KHCO3, a type ofreactive carbon solution, rather than gaseous CO2. The reactor uses H+deliveredby a bipolar membrane to form CO2at the cathode. This CO2is subsequentlyreduced into methane. A cationic surfactant added to the catholyte suppressed hydrogen evolution and increased methaneformation. A 1D continuum model confirmed that H+from the membrane promotes the formation of methane overmulticarbon products at the cathode. Thesefindings present design principles for electrochemical methane synthesis.

Automated summary

We report the development of an electrochemical reactor that can convert 3.0 M KHCO3 into methane, achieving a methane yield of 34%, compared to the previously reported highest yield of 3%. The reactor utilizes a reactive carbon solution and a cationic surfactant in the catholyte to suppress hydrogen evolution and increase methane formation. Furthermore, a 1D continuum model confirms the significant role of H+ transported by a bipolar membrane in promoting methane formation over multicarbon products. These findings provide important design principles for electrochemical methane synthesis.