Three-Dimensionally Ordered Macroporous Superstructure of Nitrogen-Doped Hierarchical Porous Carbon Implanted with Ultrafine Pd Nanoclusters for the Efficient Methanol Oxidation Reaction

High-performance catalysts for the methanol oxidation reaction (MOR) are critical for advancing direct methanol fuel cells. Here, we report a three-dimensionally ordered macroporous superstructure of nitrogen-doped hierarchical porous carbon (NHPC) implanted with ultrafine Pd nanoclusters (∼1.8 nm) as a highly efficient electrocatalytic micronano reactor (Pd/NHPC). Constructed via nanocasting of ZIF-8 on polystyrene colloidal crystals, followed by the confined growth of Pd, this architecture features interconnected macropores that maximize mass transport and active-site exposure. In alkaline media (1.0 M KOH + 1.0 M CH3OH), Pd/NHPC achieves a mass activity of 7383 mA mgPd–1─surpassing commercial Pt/C and Pd/C by factors of 4.09 and 3.80, respectively. It exhibits exceptional stability, retaining 95.0% activity after 500 cycles at 200 mV s–1, and delivering 2373 mA mgPd–1 after 7200 s chronoamperometry. Mechanistic studies reveal that the hierarchical porosity accelerates reactant diffusion/intermediate desorption, while optimized nitrogen configurations (pyridinic/pyrrolic/graphitic-N) enhance metal–support interaction, enrich electron density on Pd0 sites, and facilitate a direct (CO-poisoning-free) MOR pathway. This work establishes a paradigm for designing stable, high-activity nanocatalysts through synergistic structural and electronic engineering.