为探索CO2气体在低温等离子体中的分解规律,开展了近室温条件下,射频等离子体中CO2及CO2-H2混合气体的电离分解行为研究.反应产物通过差分四极质谱进行在线分析,并通过发射光谱对等离子体状态进行诊断.研究结果表明,在射频电场作用下二氧化碳气体迅速电离并部分分解为一氧化碳和氧气,随着射频功率升高CO2分解率提高,而能量效率降低.氢气的加入可以显著降低CO2分解达到平衡所需的时间,随着H2含量的增加,二氧化碳的分解率先降低后升高,H2的电离状态与对CO2分解氧的消耗是导致CO2分解率V字形变化的主要原因.%Currently,worldwide attention is focused on controlling the continually increasing emissions of greenhouse gases,especially carbon dioxide.To this end,a number of investigations have been carried out to convert the carbon dioxide molecules into value-added chemicals.As carbon dioxide is thermodynamically stable,it is necessary to develop an efficient carbon dioxide utilization method for future scaled-up applications.Recently,several approaches,such as electrocatalysis,thermolysis,and non-thermal plasma,have been utilized to achieve carbon dioxide conversion.Among them,non-thermal plasma,which contains chemically active species such as high-energy electrons,ions,atoms,and excited gas molecules,has the potential to achieve high energy efficiency without catalysts near room temperature.Here,we used radio-frequency (RF) discharge plasma,which exhibits the non-thermal feature,to explore the decomposition behavior of carbon dioxide in non-thermal plasma.We studied the ionization and decomposition behaviors of CO2 and CO2-H2 mixtures in plasma at low gas pressure.The non-thermal plasma was realized by our custom-made inductively coupled RF plasma research system.The reaction products were analyzed by on-line quadrupole mass spectrometry (differentially pumped),while the plasma status was monitored using an in situ real-time optical emission spectrometer.Plasma parameters (such as the electron temperature and ion density),which can be tuned by utilizing different discharge conditions,played significant roles in the carbon dioxide dissociation process in non-thermal plasma.In this study,the conversion ratio and energy efficiency of pure carbon dioxide plasma were investigated at different values of power supply and gas flow.Subsequently,the effect of H2 on CO2 decomposition was studied with varying H2 contents.Results showed that the carbon dioxide molecules were rapidly ionized and partially decomposed into CO and oxygen in the RF field.With increasing RF power,the conversion ratio of carbon dioxide increased,while the energy efficiency decreased.A maximum conversion ratio of 77.6％ was achieved.It was found that the addition of hydrogen could substantially reduce the time required to attain the equilibrium of the carbon dioxide decomposition reaction.With increasing H2 content,the conversion ratio of CO2 decreased initially and then increased.The ionization state of H2 and the consumption of oxygen owing to CO2 decomposition were the main reasons for the V-shape plot of the CO2 conversion ratio.In summary,this study investigates the influence of power supply,feed gas flow,and added hydrogen gas content,on the carbon dioxide decomposition behavior in non-thermal RF discharge plasma.
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