Significantly Enhanced Oxygen Reduction Reaction Activity in Co-N-C Catalysts through Synergistic Boron Doping

The weak adsorption energy of oxygen-containing intermediates on Co center leads to a considerable performance disparity between Co-N-C and costly Pt benchmark in catalyzing oxygen reduction reaction (ORR). In this work, we strategically engineer the active site structure of Co-N-C via B substitution, which is accomplished by the pyrolysis of ammonium borate. During this process, the in-situ generated NH3 gas plays a critical role in creating surface defects and boron atoms substituting nitrogen atoms in the carbon structure. The well-designed CoB1N3 active site endows Co with higher charge density and stronger adsorption energy toward oxygen species, potentially accelerating ORR kinetics. As expected, the resulting Co-B/N-C catalyst exhibited superior ORR performance over Co-N-C counterpart, with 40 mV, and fivefold enhancement in half-wave potential and turnover frequency (TOF). More importantly, the excellent ORR performance could be translated into membrane electrode assembly (MEA) in a fuel cell test, delivering an impressive peak power density of 824 mW·cm–2, which is currently the best among Co-based catalysts under the same conditions. This work not only demonstrates an effective method for designing advanced catalysts, but also affords a highly promising non-precious metal ORR electrocatalyst for fuel cell applications.