Single Ni active sites with a nitrogen and phosphorus dual coordination for an efficient CO₂ reduction

Transition metal single-atom catalysts (SACs) have emerged as a research hotspot in CO₂RRs. However, tuning the electronic configuration of a metal single-atom by employing new heteroatoms still remains a challenge. Herein, a carbon matrix loaded with a N and P co-coordinated Ni single-atom (denoted as Ni-NPC) was prepared for an efficient CO₂RR. XANES and EXAFS were conducted to explore the coordination environment and charge distribution of the Ni-NPC catalyst. DFT calculations indicated that the Ni atom gained electrons from the P atom, and the Ni-NPC sample had a decreased energy barrier of +0.97 eV after doping with P atoms, which was favorable to overcome the limiting-step bottleneck for promoting CO₂RR. Due to the rich Ni atomic active sites and superior P-doping effect, Ni-NPC exhibited a maximum FE_CO of 92% with a high current density of 22.6 mA cm^-2 at -0.8V vs. RHE, which was far superior to those of NC, NPC and Ni-NC catalysts. Moreover, both the FE_CO and current density of the Ni-NPC catalyst remained stable for more than 16 h at -0.8 V vs. RHE, indicating a high stability for long-term CO₂RR experiments.