Engineering iron carbide catalyst with aerophilic and electron-rich surface for improved electrochemical CO2 reduction

Enhancing Electrocatalytic CO2-to-CO Conversion by Weakening CO Binding through Nitrogen Integration in the Metallic Fe Catalyst

Metallic iron (Fe) typically demonstrates the unfavorable catalytic activity for the CO2 reduction reaction (CO2RR), mainly attributed to the excessively strong binding of CO products on Fe sites. Toward this end, we employed an effective approach involving electronic structure modulation through nitrogen (N) integration to enhance the performance of the CO2RR. Here, an efficient catalyst has been developed, composed of N-doped metallic iron (Fe) nanoparticles encapsulated in a porous N-doped carbon framework. Notably, this N-integrated Fe catalyst displays significantly enhanced performance in the electrocatalytic reduction of CO2, yielding the highest CO Faradaic efficiency of 97.5% with a current density of 6.68 mA cm-2 at -0.7 V versus the reversible hydrogen electrode. The theoretical calculations, combined with the in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy study, reveal that N integration modulates the electron density around Fe, resulting in the weakening of the binding strength between the Fe active sites and *CO intermediates, consequently promoting the desorption of CO and the overall CO2RR process.

Study of CuSb bimetallic flow-through gas diffusion electrodes for efficient electrochemical CO2 reduction to CO

Electrochemical CO2 reduction (eCO2R) to industrially important feedstock has received great attention, but it faces different challenges. Among them, the poor CO2 mass transport due to low intrinsic CO2 solubility significantly limits the rate of reduction reactions, leading to lower catalytic performance; thereby, commercially relevant current densities can't be achieved. Moreover, the poor activity and selectivity of high-cost monometallic catalysts, including Cu, Zn, Ag, and Au, undermine the efficiency of eCO2R. Flow-through gas diffusion electrodes (FTGDE), a newly developed class of GDEs, can potentially solve the issue of poor CO2 mass transport because they directly feed the CO2 to the catalyst layer. In addition, abundant surface area, porous structure, and improved triple-phase interface make them an excellent candidate for extremely high rate eCO2R. Antimony, a low-cost and abundant metalloid, can be effectively tuned with Cu to produce useful products such as CO, formate, and C2H4 through eCO2R. Herein, a series of porous binary CuSb FTGDEs with different Sb compositions are fabricated for the electrocatalytic reduction of CO2 to CO. The results show that the catalytic performance of CuSb FTGDEs improved with increasing Sb content up to a certain threshold, beyond which it started to decrease. The CuSb FTGDE with 5.4 g of antimony demonstrated higher current density (206.4 mA/cm2) and faradaic efficiency (72.82 %) at relatively lower overpotentials. Compared to gas diffusion configuration, the poor catalytic activity and selectivity achieved by CuSb FTGDE in non-gas diffusion configuration signifies the importance of improved local CO2 concentration and improved triple-phase interface formation in GDE configuration. The several hours stable operation of CuSb FTGDEs during eCO2R demonstrates its potential for efficient electrocatalytic conversion applications.