NH3 thermal treatment on N‐enriched carbon materials is adopted for creating a high density of topological defects by eliminating pyrrolic‐N and pyridinic‐N dopants from carbon materials. It is found that content of pyridinic‐N and pyrrolic‐N in the carbon precursor and the NH3 thermal‐treatment temperature play critical roles in the creation of topological defects during the NH3‐induced removal process, determining the CO2RR performance.
Abstract
Topological defects, with an asymmetric local electronic redistribution, are expected to locally tune the intrinsic catalytic activity of carbon materials. However, it is still challenging to deliberately create high‐density homogeneous topological defects in carbon networks due to the high formation energy. Toward this end, an efficient NH3 thermal‐treatment strategy is presented for thoroughly removing pyrrolic‐N and pyridinic‐N dopants from N‐enriched porous carbon particles, to create high‐density topological defects. The resultant topological defects are systematically investigated by near‐edge X‐ray absorption fine structure measurements and local density of states analysis, and the defect formation mechanism is revealed by reactive molecular dynamics simulations. Notably, the as‐prepared porous carbon materials possess an enhanced electrocatalytic CO2 reduction performance, yielding a current density of 2.84 mA cm−2 with Faradaic efficiency of 95.2% for CO generation. Such a result is among the best performances reported for metal‐free CO2 reduction electrocatalysts. Density functional theory calculations suggest that the edge pentagonal sites are the dominating active centers with the lowest free energy (ΔG ) for CO2 reduction. This work not only presents deep insights for the defect engineering of carbon‐based materials but also improves the understanding of electrocatalytic CO2 reduction on carbon defects.
