Research On Microplasma Catalytic Oxidation Of CO Driven By Triboelectric Nanogenerator And Its Reaction Mechanism

CO catalytic oxidation reaction is a common model reaction,which has potential application value in the fields of vehicle exhaust treatment,Pt fuel cell protection,environmental pollutant elimination and activity evaluation of nanocatalysts.The active species of oxygen in CO oxidation reaction and the effective regulation of its entry path into CO₂ are the keys to designing an efficient catalytic system.At present,CO catalytic oxidation reaction is mainly divided into two catalytic systems according to the activation mode of oxygen.The first is a noble metal-based catalytic system in which oxygen atoms are introduced from oxygen.The activation of oxygen is the primary step of the reaction.For noble metal/reducing oxide catalytic systems,it is generally accepted that the interface between metal and oxide plays an vital role in oxygen activation.Noble metal catalytic systems have the advantages of high reactivity and low starting temperature,but their scarcity and high price limit their use.The second type is the transition metal oxide catalytic system,in which the oxygen atoms entering the products are partly from the lattice oxygen in the oxide and partially from the oxygen.Activation of lattice oxygen is a rate-limiting step for such reactions.The advantage of such catalytic systems is that they are cheap and abundant.Due to the large bond energy of the metal-oxygen bond,a large amount of energy is needed to break the metal-oxygen bond,so the reaction is usually carried out at a higher temperature.At present,in the CO oxidation reaction,researcher focus on oxygen and lattice oxygen activation respectively.Oxygen activation and lattice oxygen activation are equally important in CO oxidation and affect each other.At low temperature,it is difficult for reactive oxygen species adsorbed on the surface to change into lattice oxygen species,resulting in the activation of both oxygen and lattice oxygen.Therefore,the activation of both lattice oxygen and oxygen at low temperature remains a challenge.In recent years,renewable energy such as electric energy,solar energy,and so on has aroused people's wide attention.Mechanical energy is also a renewable energy source,such as wind,water,and so on.However,there is still a lack of examples of using mechanical energy to catalyze chemical reactions.The triboelectric nanogenerator?TENG?is a way of utilizing mechanical energy,with output voltages of up to several thousand volts,to produce microplasma by ionizing a variety of gases such as oxygen and nitrogen.The microplasma contains a large number of active ions,and the energetic active ions may interact with the oxide surface.Thus,the micro-plasmas generated from TENG promise to activate both lattice and molecular oxygen on cheap oxides,meanwhile providing a new way to use mechanical energy to drive catalytic chemical reactions.In this paper,a novel catalytic system was developed to catalyze CO oxidation at room temperature by combining the micro-plasma generated from TENG with the transition metal oxides.The research contents of this paper mainly include the following two parts:1.Construction of gas discharge microplasma catalytic system driven by TENG and study on CO oxidation reaction: A novel catalytic system was developed by combining the microplasma generated by TENG-driven gas discharge with transition metal oxides.With an output voltage of up to 2.5 k V,TENG is able to drive gas discharges to produce microplasma.The electrical output curve of microplasma catalysis system varies with distance,speed,and discharge mode.Transition metal oxides are generally capable of promoting CO oxidation to CO₂ in microplasma catalytic systems,while the light and heat associated with the microplasma generated by TENG play a weak role in CO catalytic reactions.The experimental results show that the optimal catalytic activity of the MnO₂ catalyst is obtained when the discharge distance is 0.15 mm,the discharge mode is AC and the TENG speed is 400 rpm.The cyclic experiments show that the activity and initial rate of the catalyst remain stable in the microplasma catalytic system.At the same time,the morphology and structure of MnO₂ catalyst before and after the action of microplasma were characterized,and there was no obvious change before and after the reaction,that indicating the microplasma has no effect on the morphology and crystal structure of MnO₂ catalyst2.Mechanism study of CO oxidation catalyzed by gas discharge microplasma driven by TENG: on the basis of the above,we studied the mechanism in detail.The activated species of oxygen in the CO oxidation reaction and its entry path into CO₂ were mainly studied.Isotopic tracing experiments were accompanied with ¹³CO and 18O₂.The results showed that the oxygen atom of ¹³C¹⁶O¹⁸ O in the product CO₂ of CO oxidation reaction was derived from oxygen,and the oxygen atom of ¹³C¹⁶O₂ was derived from the lattice oxygen of oxide.The XPS and EPR implementations show that the microplasma can activate the lattice oxygen on the surface,and the activated lattice oxygen participates in the CO oxidation reaction.The catalytic oxidation activity of CO under CO/He anaerobic atmosphere indicated that the lattice oxygen on the surface of MnO₂ catalyst was activated and participated in the CO reaction.The chromogenic experiment of the NBT solution showed that the microplasma activated the oxygen in the gas phase and produced a large number of O₂^-free radicals.In the microplasma catalysis system,the microplasma can realize the activation of both gas-phase oxygen and oxide lattice oxygen.This is also the fundamental reason for the high activity of transition metal oxides at room temperature.The mechanism of CO catalytic oxidation reaction was also discussed,and it was found that the reaction followed the Mv K mechanism of modification,and O₂^-active ion filled the oxygen vacancy of the MnO₂ catalyst.In this paper,a TENG driven gas discharge microplasma and a cheap transition metal oxide catalytic system were constructed,The microplasma was driven by mechanical energy to achieve the purpose of simultaneously activating the lattice oxygen on the catalyst surface and the oxygen in the phase,that achieving the efficient catalytic conversion of CO at room temperature and pressure.The microplasma-transition metal oxide catalytic system has the advantages of low price and low energy consumption,and has a broad application prospect.This paper not only provides a method to realize low-temperature CO oxidation reaction,but also opens up a new way to drive catalytic reaction by mechanical energy.