Abstract: In this study, copper nanoparticles are supported on porous carbon papers by airbrushing; they are then coupled with a Nafion 117 membrane to form working electrodes for the continuous production of methane through gas-phase electroreduction of CO2 in a filter-press electrochemical cell. The methane production and Faradaic efficiency (FE) are evaluated and compared at different applied voltages (from ?1.8 to ?2.4?V vs. Ag/AgCl) and catalyst loadings (0.25, 0.5, 1, and 1.5?mg?cm?2). The maximum methane production rate is achieved at ?2?V and 0.5?mg?cm?2 (4.4??mol?m?2?s?1) whereas the highest Faradaic efficiencies can be obtained at 1?mg?cm?2 (FE=10.1?%) and at ?1.8?V (FE=12.1?%). The role of the porous carbon support and the possibility of humidifying the CO2 stream before it enters the cell are also tested. These results may provide a new understanding of the use of gas?liquid electrochemical membrane reactors for the direct conversion of CO2 in the gas phase.

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