ZIF-derived porous carbon supported cobalt and selenium dual sites enhanced oxygen reduction reaction

Non-noble metal based oxygen-reduction electrocatalysts with high performance in acidic medium are of great importance to application of proton exchange membrane fuel cells (PEMFCs). Dual-sites catalysts with rational design are essential to promote the sluggish kinetics of oxygen reduction reactions (ORR) owing to the synergistic effect. However, the study of dual sites is mainly based on metal atom pairs and need further mechanism exploration for guiding the reasonable design. Herein, a novel designed dual-sites electrocatalyst with high dispersed Co-Nx and Se-C dual sites embedded in ZIF-derived porous carbon frameworks was successfully synthesized, which displayed a positive ORR activity with a half-wave potential of 0.764 V (vs. RHE) as well as a high stability in 0.5 M H2SO4. Besides, the prepared Co-Se-N-C-2 sample exhibited a high ORR activity with a peak power density of 297 mW cm-2 and a low charge-transfer resistant of 0.326 & omega; when this catalyst was employed in the H2/O2 fuel cell test. Furthermore, experimental characterizations and theoretical calculations revealed that the constructed Co/Se dual sites had multiple effects. In addition to providing additional active sites, the introduction of Se can effectively modulate the charge redistribution, enhance the efficiency of charge transfer, and reduce the energy barrier of the desorption process of the ORR pathway. These multiple effects promote the ORR kinetics and improve the catalytic performance.