Nonprecious Catalyst for Three-Phase Contact in a Proton Exchange Membrane CO₂ Conversion Full Cell for Efficient Electrochemical Reduction of Carbon Dioxide

Development of a cost-effective and highly efficient electrocatalyst is essential but challenging in order to convert carbon dioxide to value-added chemicals at ambient conditions. In the current work, the activity of a full electrochemical cell has been demonstrated, utilizing a proton exchange membrane CO₂ conversion cell that can selectively convert carbon dioxide to a value-added chemical (formic acid) at room temperature and pressure. A cost-effective, nonprecious-metal-based electrocatalyst, nitrogen-doped carbon nanotubes encapsulating Fe₃C nanoparticles (Fe₃C@NCNTs), has been reported to exhibit superior catalytic activity toward the electrochemical CO₂ reduction reaction (CO₂RR). A facile one-step synthesis procedure has been undertaken to synthesize Fe₃C@NCNTs. CO₂ adsorption takes place via sharing of charge between the nucleophilic anchoring site (Fe₃C) and the electrophilic C site of CO₂, as shown by the DFT studies. The porous architecture, unique tubular structure, high graphitization degree, and appropriate doping of the Fe₃C-encapsulating NCNTs allow better three-phase contact of CO₂ (gas), H₂O (liquid), and catalyst (solid), which can enhance the electrocatalytic activity of the cell, as demonstrated by the experimental findings. The cell was tested under a continuous flow of CO₂ gas and has been demonstrated to produce a good amount of formic acid (HCOOH). The production of formic acid was examined by utilizing UV-vis spectroscopy and high-performance liquid chromatography (HPLC). A series of designed experiments disclosed that the maximum yield of formic acid was as high as 90% with Fe₃C@NCNTs as both anode and cathode catalysts. Technology to scale up the reduction procedure has also been proposed and shown in this particular work. These unique observations open a route for the development of cost-effective and highly active platinum-free electrocatalysts for the CO₂RR.