Modification of pyridinic N and O-rich defects in a bifunctional electrocatalyst with enhanced electrocatalytic performance.

The modification of active sites in electrocatalysts is important for energy conversion and storage systems. Here, CoO x /N-doped graphene/polymeric carbon nitride (CoO x /NG/PCN) hybrid was prepared by thermal annealing method. The introduction of NG greatly prevented the aggregation of CoO x nanoparticles. Further doping PCN into CoO x /NG, CoO x /NG/PCN showed wrinkle and cross-linked structure. And the introduction of PCN can effectively increase the contents of pyridinic N and numbers of O defects to result in the improved oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. Detailed experiments suggested that the onset and half-wave potentials (E onset and E 1/2) of CoO x /NG positively shifted of 110 and 100 mV, respectively compared to pure CoO x nanoparticles. When further doping PCN into CoO x /NG, E onset and E 1/2 were further positively shifted of 40 and 110 mV, respectively. More importantly, such ORR activity exhibited comparative activity and even more superior stability and excellent methanol tolerance than commercial Pt/C. Additionally, the resulted CoO x /NG/PCN also showed superior OER activity. Compared with CoO x /NG and CoO x , the overpotential of CoO x /NG/PCN for 10 mA/cm2 current densities was decreased for 160 mV and 180 mV, respectively. Especially, the investigation herein may assist in a new insight to bond configurations modification of catalysts and can be extended to other catalytic systems. Synopsis: CoO x /NG/g-C 3 N 4 as bifunctional electrocatalyst for OER and ORR. Image 1 • A simple thermal treatment process to prepare CoO x /NG/g-C 3 N 4. • CoO x /NG/g-C 3 N 4 as a superior bifunctional electrocatalyst for ORR and OER. • Increasing density of O defects and pyridinic N can boost electrocatalytic activity. [ABSTRACT FROM AUTHOR]