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

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%.