Hydrogen concentration effects on electron energy and hydrogen radical in atmospheric-pressure argon/hydrogen dielectric barrier discharge for bio-oil upgrading

The environment-friendly refinement of bio-oil enhances its compatibility with future energy needs, increasing its practical viability. Plasma-assisted hydrodeoxygenation provides a mild, green, and efficient approach for bio-oil upgrading, though its efficiency requires further enhancement. To maintain high plasma activity under mild conditions, this work focuses on effectively modulating electron energy and H radical density —critical parameters governing bio-oil conversion performance. Using a one-dimensional fluid model, we simulate an atmospheric-pressure argon/hydrogen pulsed dielectric barrier discharge, focusing on H₂ concentration effects on electron energy distribution and H radical density. Results show that the increased H₂ % drives a transition from heavy Ar ions (Ar⁺, ArH⁺) to light H ions (H₃⁺, H⁺) through specific ion-production/loss reactions, reducing effective ion mass from 40 to 3 amu. The lighter ion population elevates average electron energy by lowering sheath potential and modifying energy dissipation pathways. An optimal H₂ concentration range (1–10 %) maintains high electron energy (2.6–2.8 eV) and H density (about 10¹³ cm⁻³) essential for plasma stability and efficient bio-oil hydrodeoxygenation. This work offers fundamental theoretical insights and parametric guidelines for developing plasma-assisted bio-oil conversion toward high-quality biofuels.