Hydrogen-Bond-Assisted Synthesis of Single-Atom and Nanocluster Synergistic Sites for Enhanced Oxygen Reduction Reaction

Electrocatalysts combining metal single-atom and nanocluster synergy are promising alternatives to platinum-based catalysts for oxygen reduction reaction (ORR). However, controllable synthesis of such catalysts with high ORR performance remains challenging due to metal atom aggregation into large nanoparticles. Here, a hydrogen-bond network confinement approach to construct Co nanocluster and Co-Nx-C moiety coexisting active sites on nitrogen-doped porous carbon for highly active and long-term stable ORR is reported. The optimized Co@Co-N-C catalyst exhibits a half-wave potential (E1/2) of 0.92 V versus RHE and a limiting current density (JL) of 6.02 mA cm-2 for ORR, presenting a 40 mV positive shift in E1/2 than the competitor with the highest JL and 15.7% improvement in JL over the catalyst with the most positive E1/2. The enhanced catalytic performance originates from the synergy between Co nanocluster and Co-Nx-C moieties, which modulates the electronic structure of the Co-based active sites and improves the electrochemically active surface area. The zinc-air battery assembled with Co@Co-N-C catalyst delivers a specific capacity of 870 mAh g-1 and a maximum discharge power density of 210 mW cm-2, representing approximate to 52% improvement over Pt/C-based devices. This hydrogen-bond-assisted synthesis strategy opens pathways for designing high-performing catalysts in diversified fields beyond ORR, including water splitting, CO2 reduction, and nitrogen reduction.