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Description
Most ZIF-derived carbons are rich in micropores, which slows oxygen transport to single-atom sites [1, 2]. We report a template-free, CNC-guided route that builds mesopores at the precursor stage and fixes atomically dispersed Co-N₄ centers in carbon. During in situ assembly, Co/ZIF-8 nucleates densely on cellulose nanocrystals and forms thin, open shells. After pyrolysis and acid washing, these shells turn into interconnected 4-6 nm channels within a conductive framework. XAS shows Co bonded to nitrogen and no Co-Co contribution, confirming isolated Co atoms [3]. Nitrogen sorption reveals that mesopore volume increases with the Co/Zn ratio while the micropore fraction stays nearly constant, so the extra porosity mainly comes from mesopores set by the assembly step rather than created by leaching. This architecture improves access to Co-N₄ sites and wets the electrode more effectively [4]. In alkaline media the catalyst gives a high half-wave potential (~0.85 V), a 55.9 mV dec-1 Tafel slope, and stable activity under repeated LSV cycling (100000 cycles). Using cellulose nanocrystals-a green, water-processable feedstock-avoids hard templates and harsh activation, lowers cost and waste, and is well suited to scale-up. This work shows a simple path to durable Co-N₄ catalysts with programmed mesoporosity.
