Ionic Liquids Modulating Local Microenvironment of Ni–Fe Binary Single Atom Catalyst for Efficient Electrochemical CO₂ Reduction

Abstract

The Ni and Fe dual-atom catalysts still undergo strikingly attenuation under high current density and high overpotential. To ameliorate the issue, the ionic liquids with different cations or anions are used in this work to regulate the micro-surface of nitrogen-doped carbon supported Ni and Fe dual-atom sites catalyst (NiFe-N-C) by an impregnation method. The experimental data reveals the dual function of ionic liquids, which enhances CO₂ adsorption ability and modulates electronic structure, facilitating CO₂ anion radical (CO₂ ^•¯) stabilization and decreasing onset potential. The theoretical calculation results prove that the attachment of ionic liquids modulates electronic structure, reduces energy barrier of CO₂ ^•¯ formation, and enhances overall ECR performance. Based on these merits, BMImPF₆ modified NiFe-N-C (NiFe-N-C/BMImPF₆) achieves the high CO faradaic efficiency of 91.9% with a CO partial current density of -120 mA cm^-2 at -1.0 V. When the NiFe-N-C/BMImPF₆ is assembled as cathode of Zn-CO₂ battery, it delivers the highest power density of 2.61 mW cm^-2 at 2.57 mA cm^-2 and superior cycling stability. This work will afford a direction to modify the microenvironment of other dual-atom catalysts for high-performance CO₂ electroreduction.