Flash Synthesis of Graphite-Encapsulated NiMn Heterostructures for Efficient Hydrogen Production and Biofuel Valorization

Hydrogen and bioderived fuels are central for decarbonizing energy systems, yet catalyst deactivation and inefficient synthesis methods remain major bottlenecks. Herein, we report a rapid strategy to synthesize graphite-encapsulated NiMn heterostructured nanoparticles via a rapid high-temperature carbothermal shock (HCS). Structural characterization reveals a dual-phase architecture comprising Mn-incorporated face-centered cubic Ni (fcc-Ni) and MnO phase, synergistically enhancing bond cleavage within complex reactions. The optimized catalyst achieves an 18.7-fold increase in hydrogen yield (8.4 ± 0.3 mmol/g_biomass-daf, 40.3 ± 0.9 vol %) compared to noncatalytic pyrolysis, while simultaneously enabling complete conversion of various lipid feedstocks, particularly fatty acid methyl ester (FAME), into biojet and diesel-range hydrocarbons via dominant decarboxylation (DCO₂) pathways. The catalyst maintains over 80% efficiency over seven cycles, and its catalytic activity can be effectively restored through a rapid shock-based regeneration strategy. Mechanistic studies further reveal that the heterostructure design and shell structure modulation enhance bond activation and promote reaction kinetics. This work demonstrates the effectiveness of HCS as a platform for engineering Ni-based nanomaterials, potentially bridging biomass-to-hydrogen conversion with biofuel upgrading for integrated biorefineries.