Construction of electron-rich nickel single atom catalyst by heteroatom doping for enhanced CO2 electroreduction

Abstract

Adjustment of electron distribution by heteroatom doping has emerged as a promising strategy to improve the electrochemical CO₂ reduction (ECR) performance of nickel single atom catalysts. Herein, density functional theory calculation (DFT) verifies that the doping of phosphorus atoms in the first shell regulates the valence state of the nickel centre and facilitates higher electron density in the outer shell, which is beneficial to intermediate adsorption, electron transfer and the decrease of reaction energy barrier, resulting in outstanding ECR performance. Guided by the theoretical calculation results, the asymmetrical nickel single atom catalyst doped with phosphorus atom was successfully fabricated by phytic acid modification and calcination treatment. X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy prove that the valence state of nickel exhibits a negative shift and makes them electron-rich after doping phosphorus atom, which is consistent with DFT results. Such catalyst displays superior ECR performance with CO faradaic efficiency above 90 % at a wide potential range and a high CO partial current density of −244.1 mA cm⁻² at −1.0 V in flow cell. The asymmetric electron regulation strategy can be potentially applied to the other transition metal single atoms to enhance their catalytic performance.