Effective Strategy to Develop a Metal-Free Nitrogen-Doped Carbon with Abundant Intrinsic Carbon Defects for Electrochemical CO2 Reduction

Abstract

For the practical application of carbon dioxide electrochemical reduction reaction (CO₂RR), developing efficient metal-free carbon-based electrocatalysts is extremely important. To date, various heteroatom-doped carbon materials for CO₂ reduction have been synthesized. Even though intrinsic carbon defects are expected to tune the electrocatalytic activity of carbon materials such as heteroatom doping, the role of intrinsic carbon defects has received little attention. Furthermore, it is still challenging to controllably introduce intrinsic carbon defects into a carbon matrix at high density. In this work, a rational strategy to fabricate the high-density intrinsic carbon defects is provided by the sequential processes of the evaporation of atomically dispersed Zn and the removal of pyridinic N species at a pore edge from a single-atom Zn catalyst derived from a carbonized metal–organic framework. From the controlled experimental results, the removal of Zn–N_x can lead to creating the abundant intrinsic carbon defects into the carbon matrix. The optimized defective N-doped carbon materials (DNC-1200-L) exhibited excellent electrocatalytic activity, with a Faradaic efficiency (FE_CO) of 93.0% for CO generation. Notably, DNC-1200-L displayed a high-plateau FE_CO over 90.0% under the potential range from −0.6 to −0.9 V vs RHE. This study offers a simple and effective strategy for developing carbon-based electrocatalysts with high-density intrinsic carbon defects to selectively enhance the CO₂RR into CO.