Hierarchical Porous Carbon Anchored Atomic/Clustered Cobalt for Boosting Oxygen Reduction Electrocatalysis

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AbstractHierarchical porous carbon with highly active sites has emerged as an ideal support for high‐performance oxygen reduction reaction (ORR) electrocatalysts. By tuning the geometric size and coordination environment of transition metals on hierarchical porous carbon to optimize the catalytic performance for ORR, cobalt (Co) single atoms and Co nanoclusters were synthesized respectively on N‐doping and vacancy‐defective hierarchical porous carbon. Benefited from the high surface area and enhanced mass transfer, cobalt nanoclusters on nitrogen doped hierarchical porous carbon shows a high four‐electron selectivity for ORR. It presents a half wave potential of 0.854 V vs. RHE, which is comparable to that of commercial Pt/C catalysts (0.852 V vs. RHE). Meanwhile, the single‐atomic cobalt coordinated with vacancy‐defective carbon favors the two‐electron reduction of O2 to hydrogen peroxide (H2O2). It exhibits an apparent promotion on selectivity of two‐electron route with a high H2O2 selectivity of around 90 %. This work demonstrates that hierarchical porous carbons could be effectively tuned for applications that favors either four‐electron or two‐electron ORR pathway.