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[Display omitted] • An initial reaction mechanism for plasma-assisted steam reforming of toluene. • Over 60 % toluene was converted into small molecules (H 2 , CO, C 2 H 2) at 300 °C. • Combining kinetic modeling of plasma reactions and quantitative analysis of OES. • Interaction mechanism of plasma species and radicals was unveiled. • Synergy rules for plasma and thermal processes have been preliminarily obtained. Plasma-enhanced reforming has been widely studied as an efficient technology for online tar removal. By combining reforming experiments with kinetic modeling and in-situ optical emission spectrometry (OES) analysis, interaction mechanism and coupling rules of plasma/thermal reactions during plasma-assisted steam reforming of toluene were well explored in this study. A chemistry model was innovatively developed for plasma-assisted steam reforming of toluene, and predicted experimental results under different operations conditions with superb agreements. The rate of production and sensitivity analysis implied that OH, H and N 2 * mainly contributed to primary toluene conversion, while the electronic attachment dissociation of H 2 O, H addition onto benzene ring and benzyl oxidation by OH were the most enhancing-sensitive reactions. Resultantly, toluene conversion was greatly increased with steam addition before Vf H2O = 10 %, but after which Vf H2O increase deteriorated the reforming performance due to the inhibition of E-N 2 collision by high Vf H2O. As temperature increased, plasma and thermal synergistically promoted reforming performance before 300 °C, at which > 60 % toluene was converted into small molecules such as CO, H 2 and C 2 H 2, with yields of 23.6 %, 9.4 % and 16.3 % correspondingly at 12 kJ/L, but further temperature increase would not benefit due to the reduced discharge field strength at higher temperatures, being confirmed by the decreased relative intensity of OH, CN feature bands on OES. It was initially proposed that non-thermal plasma governed the reforming process at T < 300 °C, and thermal reactions predominated at T > 500 °C after a transition region (300 ∼ 500 °C). Increase of input energy caused higher discharge field strength, promoted the electronic collision ionization or dissociation of N 2 and H 2 O, thus enhanced toluene conversion and gas yields. A detailed reaction pathway has also been clarified. [ABSTRACT FROM AUTHOR]

• Multiple field parameters investigation of plasm-enhanced CO 2 spliting. • A combination analysis of optical emission spectrum and multiphysics simulation of plasma process. • Trade-off effects of plasma power and gas flow on conversion and energy efficiency. • A reduced plasma chemistry set for CO 2 dissociation. • Dissociation reactions of neutrals and electron impact reactions dominated CO 2 splitting. CO 2 dissociation in DBD plasma was thoroughly studied by combining dissociation experiments, multi-physics coupling simulation and in-situ emission spectroscopy measurements. Evolution of spatial–temporal distributions of key field parameters such as discharge mode, electron density (N e), electron temperature (T e), intermediate concentration and reaction rates were analyzed in depth, to uncover the underlying reaction mechanism. The specific energy input (SEI) had a large impact on CO 2 conversion and energy efficiency, and there was a trade-off between plasma power and gas flow rate. The highest CO 2 conversion was achieved a maximum of 15.5% at SEI = 177 J·cm−3 in this work. Meanwhile, the spectrum shows that there was a large amount of CO 2 +, CO, O, and O 2 in the plasma. In addition, we proposed and validated a reduced CO 2 splitting plasma chemistry set to explore the field parameter and key reactin rates distributions. According to the multiphysics modelling, the discharge gap greatly affected the discharge form of DBD, which will subsequently influence CO 2 splitting. In discharge gap > 1.75 mm formation of discharge channels remarkably decreased, and an over small discharge gap (δ g < 1.25 mm) would restrain the electric field range, causing shorter motion path of charged particles and less free electrons, both of which hindered the conversion of CO 2. A thinner dielectric layer can promote CO 2 conversion, due to the reduction in breakdown field strength and increase of high-energy electrons. Electron impact reactions (e + CO 2 → CO + O−, e− + CO 2 → CO + O + e−), reactions of the excited CO 2 * (CO 2 + CO 2 * → CO 2 + CO + O, CO 2 *+O → CO + O 2) mainly contributed to the CO 2 dissociation. [ABSTRACT FROM AUTHOR]