The palladium–salen complex was immobilized by electropolymerization onto a Pt disc electrode and applied as an electrocatalyst for the reduction of CO₂ in an aqueous solution. Linear sweep voltammetry measurements and rotating disk experiments were carried out to study the electrochemical reduction of carbon dioxide. The onset overpotential for carbon dioxide reduction was approximately −0.22 V vs. NHE on the poly-Pd(salen) modified electrode. In addition, by combining the electrochemical study with a kinetic study, the rate-determining step of the electrochemical CO₂ reduction reaction (CO₂RR) was found to be the radial reduction of carbon dioxide to the CO adsorbed on the metal.