Multi-scale screening of eco-friendly gas-phase inhibitors for hydrogen explosion suppression: Mechanistic selection of carbon dioxide and propane

Hydrogen plays a crucial role in realizing carbon neutrality. Nevertheless, its broad flammability limit and low minimum ignition energy bring severe explosion risks. To overcome the limitation of empirical screening of single inhibitors, this study establishes a multi-scale framework combining density functional theory calculations, chemical kinetic simulations, and 20-L spherical explosion experiments to screen five C 1 -C 3 hydrocarbons and two inert gases as eco-friendly gas-phase inhibitors for hydrogen explosion suppression. Electronic-structure analysis shows that C 3 H 8 retains the wide HOMO-LUMO gap characteristic of saturated hydrocarbons and has the lowest calculated H· and OH· channel barriers among the screened hydrocarbons. These common-reference barriers are used as screening descriptors. CO 2 exerts a chemical effect beyond physical dilution owing to its polarized charge distribution, evidenced by a critical suppression concentration approximately 11 percentage points lower than that of N 2 . Both C 3 H 6 and C 3 H 8 show an equivalence-ratio-dependent dual effect, promoting explosions below a critical equivalence ratio ( ϕ H2 ,c ≈ 0.8) and suppressing them above it. Compared with C 3 H 6 , C 3 H 8 exhibits weaker promotion, stronger suppression, and a lower critical concentration, reflecting a multi-stage H· consumption network revealed by kinetic analysis. These findings provide a theoretical basis for novel protective strategies against hydrogen explosions.