Enhanced CO2 electroreduction with conjugation effect tuned atomically dispersed nickel-based catalysts

Tuning the coordination number and coordinating atoms is a general strategy to control the activity of single-atom catalysts; however, this method has encountered bottlenecks in investigating the atomically dispersed Ni-N-C catalysts for efficient electrochemical CO₂ reduction reaction (eCO₂RR). Herein, we propose a strategy by modulating a ligand-conjugated structure to improve the activity of Ni-based single-atom catalysts without changing the coordinated atoms and coordination numbers. In the pyrrole-type Ni-N-C catalyst (Ni-N_Pyrrolic-C), the electron-donating conjugation effect of the pyrrole ligand reduces the electron cloud density on the N atom, resulting in stronger electron depletion around the active center Ni atom and thereby improving activity of CO₂ electroreduction to CO. The Ni-N_Pyrrolic-C possesses a notable CO partial current density of 415 mA cm⁻² with 92% CO Faradaic efficiency (FE) at a moderate potential of −0.85 V in gas diffusion electrodes (GDEs), which outperforms the pyridinic-type Ni-N-C catalyst (Ni-N_Pyridinic-C) with electron-withdrawing conjugation effect ligands.