Electrochemical Reduction of Carbon Dioxide to Formate in the Acetylene-Black Gas-Diffusion Electrode with a Tin Catalyst

Abstract An hydrophobized gas-diffusion electrode with a tin catalyst deposited onto acetylene black A437E is tested with the aim of elucidation of its potential in intensifying the CO2 electroreduction to formate in acidic and alkaline aqueous solutions. Porous electrodes with the fluoroplastic content of 40 wt %, a thickness of 0.5 mm, porosity of 60 vol %, and the tin content ≈0.7 mg/cm2 of the total electrode surface are studied. It is shown that this type of electrodes can be used in electroreduction of CO2 at a current density of up to 900 mA/cm2, a temperature of 25–55°C with the current efficiency from 74 to 96% with respect to formate. The 4 h electrolysis at a current density of 190 mA/cm2 produces a solution with the potassium formate concentration of 1.58 M. This is accompanied by the increase in the capacitance of the electric double layer from 7 to 17 mF/cm2 and the decrease in the current efficiency from 96 to 58%.