Etching-directed nitrogen doping strategy to construct efficient defective sites in carbon for electrocatalytic oxygen reduction

Abstract

Construction of synergistic coupling sites of intrinsic carbon defects and N dopants in N-doped carbon is of great significance to improve the catalytic activities of metal-free carbon-based materials toward oxygen reduction reaction (ORR). However, the carbon-defect construction and N doping by existing strategies are usually independent processes, resulting in a random arrangement of the intrinsic carbon defects and N-dopants (i.e., hardly forming the coupling sites) in the resultant carbon materials. Herein, an etching-directed nitrogen doping strategy for constructing carbon defect/N dopant coupling sites is developed, in which nitrogen is directionally doped at the freshly created intrinsic carbon defects during the synthesis of N-doped carbon. The as-prepared N-doped carbon catalyst enriched with such coupling sites renders a remarkable ORR catalytic activity with an ORR half-wave potential of 0.891 V vs. RHE and an excellent long-term durability (3% current loss after 15,000 s at 0.6 V vs. RHE). Experimental characterizations and theoretical calculations reveal the formation mechanism of the coupling sites as well as the origin of their high catalytic activities toward ORR. This etching-directed nitrogen doping strategy shows great universality for the controllable construction of active sites in carbon-based materials derived from different precursors for electrochemical energy storage and conversion applications.