Dispersed Co-N4 Sites on N-Doped Porous Carbon for High-Performance pH-Universal ORR Catalyst.

Abstract

Developing cost-effective, highly active, wide-pH oxygen reduction reaction (ORR) electrocatalysts remains a critical challenge for replacing platinum-group-metal benchmarks in emerging electrochemical energy systems. In this work, we report a facile approach to synthesize single-atom-type catalyst Co1@N4-C catalyst using renewable bacterial cellulose (BC) as the carbon source. BC's intrinsic 3D nanofibrous structure greatly suppresses active moiety agglomeration during thermal conversion, yielding uniformly dispersed Co-N4 sites in hierarchically porous carbon with excellent ORR activity under alkaline, acidic, and neutral conditions. Specifically, the catalyst delivers half-wave potentials of 0.83, 0.84, and 0.687 V (vs. RHE) in alkaline, acidic, and neutral media, respectively, values that are comparable to or even surpass those of commercial Pt/C. In addition, Co1@N4-C exhibits superior electrochemical durability, retaining 97.7%, 95.2%, and 94.1% of the initial current density after 11 000 cycles in alkaline, acidic, and neutral electrolytes, respectively. Furthermore, when integrated as the air-cathode catalyst in a zinc-air battery, the device delivers a peak power density of 122 and 125 mW cm-2 under alkaline and neutral conditions, respectively, together with excellent cycling stability, underscoring the practical promise of this catalyst for real-world energy conversion devices.

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