Flash Joule heating-driven bamboo pyrolysis for nitrogen-doped porous biochar: Process regulation and non-equilibrium synergistic mechanism

Flash Joule heating (FJH) is an emerging electrified thermochemical technology for rapid, energy-efficient biomass pyrolysis. However, how its temperature-time history regulates solid and gas yields while coupling pore development with nitrogen doping under non-equilibrium conditions remains poorly understood. Herein, FJH integrates bamboo pyrolysis, KOH activation, and in-situ nitrogen doping using melamine into a one-step process. Increasing pyrolysis temperature and holding time decreased the solid yield and increased the gas yield, while producing porous N-doped biochar within tens of seconds, with a specific surface area of 1429 m 2 g −1 and a nitrogen content of 5.8 at.%, and H 2 /CO-rich syngas. Experiments and calculations reveal a non-equilibrium synergistic mechanism. , Electrothermal simulations indicate an evolving current pathway and heating behavior during carbonization, while XRD identifies KOCN as the main crystalline K-containing phase in the quenched products, and thermodynamics favor K 2 CO 3 reduction above 1300 °C. KOCN may mediate pore formation and nitrogen anchoring at carbon-edge sites. Ultrafast heating suppresses secondary tar polycondensation, whereas rapid quenching preserves the metastable pore structure and edge-type pyridinic- and pyrrolic-N species. Density functional theory calculations reveal preferential K + interactions at edge-type N sites, providing an atomic-scale basis for their possible contribution to capacitive behavior. With renewable electricity and projected electricity-intensity scenario, net GHG emissions are 4.10 kg CO 2 -eq kg −1 feedstock, dominated by reagents. This work establishes FJH-driven pyrolysis as a rapid and electrified process for regulating solid and gas product distribution and co-producing N-doped porous biochar and H 2 /CO-rich gas, while elucidating the underlying non-equilibrium activation chemistry.