Promoting the electrocatalytic activity for Ni-based single atom catalysts by nitrogen and phosphorus codopant towards CO2 reduction

Electrochemical carbon dioxide reduction (CO2RR) is a promising approach to accomplish the CO2 net emission. Ni-based single-atom catalysts (Ni-SACs) with the Ni-N-C structure have been the hotspot in this field. However, its catalytic activity is still unsatisfied. Regulation of the coordination environment of the active site via heteroatom doping is an efficient strategy to improve its catalytic characteristics and activity. Herein, the heteroatom phosphorus is introduced into the N-doped carbon supporter to form Ni-SA/CN-P catalyst achieving the CO Faraday efficiency of 91.8% at a potential of -1.1 V along with the CO current density 91.2 mA cm-2 in the flow cell, which is superior to the sample Ni-SA/CN without P dopant. It is attributed that the more defects are built in the Ni-SA/CN-P catalyst due to the different atomic radiuses of P and N atoms. Moreover, the gap between d-band center and Femi energy level is narrowed due to the doped P atoms, which reduces the rate-limiting barrier height leading to the promoted catalytic performance. The cooperation of various items finally results in the overall performance. This work provides a simple method for establishing single-atom catalysts with P doping to improve catalytic performance for CO2RR.