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In this study, a novel type oxygen reduction reaction (ORR) electrocatalyst is explored using density functional theory (DFT); the catalyst consists of transition metal M and heteroatom N 4 co-doped in vacancy fullerene (M-N 4 -C 64 , M = Fe, Co, and Ni). Mulliken charge analysis shows that the metal center is the reaction site of ORR. PDOS analysis indicates that in M-N 4 -C 64 , the interaction between Fe-N 4 -C 64 and the adsorbate is the strongest, followed by Co-N 4 -C 64 and Ni-N 4 -C 64 . This is consistent with the calculated adsorption energies. By analyzing and comparing the adsorption energies of ORR intermediates and activation energies and reaction energies of all elemental reactions in M-N 4 -C 64 (M = Fe, Co, and Ni), two favorable ORR electrocatalysts, Fe-N 4 -C 64 and Co-N 4 -C 64 , are selected. Both exhibited conduction through the more efficient 4e - reduction pathway. Moreover, PES diagrams indicate that the whole reaction energy variation in the favorable ORR pathways of Fe-N 4 -C 64 and Co-N 4 -C 64 is degressive, which is conducive to positive-going reactions. This study offers worthwhile information for the improvement of cathode materials for fuel cells., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

An ascorbic acid/Fe 0 composite (H 2 A/Fe 0 )-activated persulfate (PS) process was provided for rhodamine B (RhB) removal. Experimental results demonstrated that the H 2 A/Fe 0 -PS system exhibits a rapid and continuous oxidation of organic contaminants, and shows great advantages over the conventional Fe 0 -PS system by significantly improving removal efficiency. This H 2 A induced dramatic enhancement for RhB degradation could be attributed to both the reduction and chelating ability of H 2 A. The H 2 A/Fe 0 composites were characterized using TEM, FE-SEM, FTIR and XPS, indicating that the obtained H 2 A/Fe 0 composites were prepared successfully. Key factors affecting the treatment were determined for the H 2 A/Fe 0 -PS system, including H 2 A/Fe 0 dosage, PS dosage, initial solution pH and temperature. Moreover, radical quenching tests revealed that sulfate radicals (SO 4 ˙ - ), hydroxyl radicals (˙OH) and superoxide radicals (O 2 ˙ - ) were generated in the H 2 A/Fe 0 -PS system, and SO 4 ˙ - was the main radical species responsible for RhB degradation. Finally, possible degradation pathways are proposed. These findings prove that the H 2 A/Fe 0 -PS system may provide a simple and effective technology for improving the degradation of refractory organic pollutants., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)