A DFT-based determination of the mechanism of electrochemical reduction of CO₂ to CO by a cobalt-Schiff base catalyst


We perform density functional theory (DFT) based calculations to investigate the reduction of carbon dioxide CO2 to carbon monixide CO using a cobalt-Schiff base catalyst, Co(salen). DFT calculated formation energies and reduction potentials showed that CO2 is reduced to CO via a [Co(salen)-COOH] intermediate. The first step of the mechanism involves the reduction of electrically neutral [Co(salen)] to [Co(salen)]anion, followed by an electrophilic addition of CO2. Furthermore, the sigma bond formed between cobalt metal center and CO2 involves a back-donation and partial charge transfer from cobalt to carbon. [Co(salen)-COOH] is further reduced to [Co(salen)-CO] and CO is released from the catalyst along with water H2O.