Improvement\nof Catalytic Activity by Nanofibrous CuInS₂ for Electrochemical\nCO₂ Reduction

Abstract

The\ncurrent study reports the application of chalcopyrite semiconductor\nCuInS₂ (CIS) nanofibers for the reduction of CO₂ to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially\nthe synthesis of CuInS₂ nanofibers was carried out by adaptable\nelectrospinning technique. To reduce the imperfection in the crystalline\nfiber, polyacrylonitrile (PAN) was selected as template polymer. Afterward,\nthe desired chemical structure of nanofibers was achieved through\nsulfurization process. Making continuous CuInS₂ nanofibers\non the cathode surface by the electrospinning method brings the advantages\nof being economical, environmentally safe, and versatile. The obtained\nnanofibers of well investigated size and diameter according to the\nSEM (scanning electron microscope) were used in electrochemical studies.\nAn improvement of Faradaic efficiency was achieved with the catalytic\nactive CuInS₂ in nanofibrous structure as compared to the\nsolution processed CuInS₂. This underlines the important\neffect of the electrode fabrication on the catalytic performance.\nBeing less contaminated as compared to solution processing, and having\na well-defined composition and increased catalytically active area,\nthe CuInS₂ nanofiber electrodes prepared by the electrospinning\ntechnique show a 4 times higher Faradaic efficiency. Furthermore,\nin this study, attention was paid to the stability of the CuInS₂ nanofiber electrodes. The electrochemical reduction of CO₂ to CO by using CIS nanofibers coated onto FTO electrodes\nwas carried out for 10 h in total. The observed current density of\n0.22 mA cm^–2 and the stability of CIS nanofiber\nelectrodes are found to be competitive with other heterogeneous electrocatalysts.\nHence, we believe that the fabrication and application of nanofibrous\nmaterials through the electrospinning technique might be of interest\nfor electrocatalytic studies in CO₂ reduction.