First principle investigation of CO2 conversion on Pd−polyaniline interface

Abstract

Electrocatalytic reduction of CO2 (ERC) in the presence of aqueous electrolyte has attracted huge attention of the scientific community due to its ability to utilize CO2 and recycle it to form renewable energy resources. The challenges behind its commercialization are: (a) poor selectivity of the catalyst towards CO2 reduction, (b) requirement of high overpotential for CO2 activation and (c) bad product selectivity of the catalyst. Recently,Weiran Zheng et. al. had proposed the use of Pd-Polyaniline (Pd-PANI) interface as a potential catalyst for ERC with very high selectivity towards the formation of formic acid. However, the mechanistic details are not yet clearly understood. Herein, with the help of density functional theory (DFT) calculation, we investigate the detailed mechanism of CO2 reduction by taking into account all possible reactions pathways on PANI and Pd-PANI. We have included the implicit solvent model to enhance the correlation of our studies with the experiment. From the studies, we observe that the solvent stabilizes the intermediates via non-covalent interactions. Our calculations suggest the activation of CO2 is robust on Pd-PANI as compared to Pd or PANI. Furthermore, ERC on PANI is selective towards *COOH (carboxyl) intermediate rather than *OCHO (formate) intermediate, while the reverse is observed on Pd-PANI. There was hardly any methanol formation on PANI whereas methanol formation occurred at a high energy cost on Pd-PANI. From our calculations, we were able to explain the reasons behind more selectivity towards formic acid rather than methanol formation and also trace amount of CO formation at high overpotential (-1.1 eV) on Pd-PANI, as observed in the experimental studies.