Efficient Electrochemical Conversion of CO2 to HCOOH Using Pd‐polyaniline/CNT Nanohybrids Prepared in Situ

Palladium has been proved to be an effective catalyst for CO2 electrocatalytic reduction. In this paper, nanostructured Pd particles fixed on polyaniline‐covered MWNTs surfaces (Pd‐PANI/CNT) were synthesized using an in situ method by reducing H2PdCl4 in a mixture of MWNTs and aniline with sodium citrate as protective stabilizer. TEM micrographs indicate that the addition of sodium citrate optimizes the size and distribution of the nanoparticles. In a 3‐electrode system, both catalysts exhibit efficient and sustainable CO2 conversion towards formate but the one with sodium citrate addition is even better. The highest faradaic efficiency happens at −0.8 V vs. SCE and can be as high as 83 %. Based on the experiments, we put forward a mechanism of Pd‐catalyzed CO2 electroreduction in aqueous solution in which Pd forms a PdHx hybrid that is involved in the reduction process with Pd.