Electrifying Schiff-based networks as model catalysts towards deeply understanding the crucial role of sp2-carbon in nitrogen-doped carbocatalyst for oxygen reduction reaction

Abstract

Deeply understanding the correlation between chemical microenvironment and oxygen reduction reaction (ORR) performance is highly desired for developing efficient heteroatom-doped carbocatalysts, yet the detailed structure of chemical microenvironment remains ambiguous. Herein, a series of nitrogen-enriched carbon composites (NEC) with controllable nitrogen configuration and regularly varied sp2 carbon content are successfully developed through a rationally designed Schiff-base chemistry approach, which provides an ideal model system to testify the detailed correlation between ORR performance and sp2 carbon chemistry. By adopting vertical ionization energies (VIE) as assessments for ORR performance, the density functional theory (DFT) calculations reveal that the nitrogen-doped carbocatalyst with high sp2 carbon content possesses remarkable electrocatalytic activity. Furthermore, an important structural parameter, electron-conductive quaternary-N site (ENS) integrating the contents of quaternary nitrogen with sp2 carbon, is proposed, which exhibits well-fitted result with the value of VIE, and agrees well with the experimental results of ORR performance. Benefiting from those advantageous nanostructures, the resultant NECs exhibits excellent catalytic activity for ORR with a high half-wave potential of 0.80 V and promising potential as cathode materials for zinc-air batteries. Therefore, the present study may open up a new avenue for the design and prediction of ORR performance on molecular level.