Ni single atoms supported on hierarchically porous carbonized wood with highly active Ni-N 4 sites as a self-supported electrode for superior CO 2 electroreduction.

Powdery N-doped carbon-supported single-atom catalysts (SACs) can be prepared on a large scale and are highly selective in converting CO 2 to CO, but their practical application is restricted by their powdery texture. Herein, we report Ni single atoms supported on hierarchically porous N-doped carbonized wood (Ni SAs-NCW) as a self-supported electrode for efficient and durable CO 2 electroreduction. The porous NCW matrix possesses an abundance of open aligned microchannels that allow unimpeded CO 2 diffusion and electrolyte transportation while the uniformly dispersed Ni SAs in the NCW matrix in the Ni-N 4 configuration afford ample highly active sites for CO 2 electroreduction. This Ni SAs-NCW electrode exhibits a high CO 2 -to-CO faradaic efficiency (FE CO ) of 92.1% and a CO partial current density ( j CO ) of 11.4 mA cm -2 at -0.46 V versus the reversible hydrogen electrode (RHE) and maintains a stable FE CO and j CO over a period of 9 h of electrolysis. This work provides an effective strategy to develop efficient SACs with potential to be integrated into flow cell systems for large-scale CO 2 reduction.