Productivity and Selectivity of Gas-Phase CO2 Electroreduction to Methane at Copper Nanoparticle-Based Electrodes

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 @2.4V vs. Ag/AgCl) and catalyst loadings (0.25, 0.5, 1, and 1.5 mgcm(-2)). The maximum methane production rate is achieved at -2 V and 0.5 mgcm(-2) (4.4 mmolm(-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.