Ni single atoms supported on hierarchically porous carbonized wood with highly active Ni–N4 sites as a self-supported electrode for superior CO2 electroreduction

Abstract

Powdery N-doped carbon-supported single-atom catalysts (SACs) can be prepared on a large scale and are highly selective in converting CO₂ 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 CO₂ electroreduction. The porous NCW matrix possesses an abundance of open aligned microchannels that allow unimpeded CO₂ diffusion and electrolyte transportation while the uniformly dispersed Ni SAs in the NCW matrix in the Ni–N₄ configuration afford ample highly active sites for CO₂ electroreduction. This Ni SAs-NCW electrode exhibits a high CO₂-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 CO₂ reduction.