Catalytic reduction of CO2 by Al–Sn-CNTs composite for synthesizing formic acid

Electrochemical reduction and photocatalytic reduction of CO2 have attracted more and more attention, but they also face the problem of low utilization efficiency of electricity and solar energy. In this study, a new strategy of applying a novel Al–Sn-CNTs composite in electrochemical corrosion process was proposed to reduce CO2 without additional electricity and light. In the Al–Sn-CNTs/CO2 system, micro galvanic cell with Al as anode and Sn or CNTs as cathode was formed, and CO2 was reduced to formic acid on the cathode surface. The cumulative formic acid concentration of the Al–Sn-CNTs/CO2 system achieved 21.18 mg/L within 60 min under the conditions of initial pH 9.0, Cl− concentration 10 mmol/L, and Al–Sn-CNTs composite dosage 2 g/L. Based on the morphology, crystal structure and electrochemical test results of the Al–Sn-CNTs composite, a possible mechanism of CO2 reduction to formic acid in the Al–Sn-CNTs/CO2 system was proposed.