| Photo-electrochemical reactions catalyzed by transition metal are widely applied in many fields,such as life-related activities,chemical synthesis,and new energy industries.In the photoelectric reaction systems,such as dye-sensitized solar cell(DSSC)and photocatalytic halogenation,the dynamic transformation among transition metal intermediates,small organic fragments and halogen acid by-products will be further pushed away from chemical equilibrium due to coupling enhancement of light and electric field,which may lead to similar nonlinear dynamic behaviors as in Belousov-Zhabotinsky oscillation.With further theoretical researches,people began to pay attention to the nonlinear oscillation behaviors which was ignored in the past study about reaction process reinforcement,and gradually realized its profound influence on transmission of energy and matters,and conversion efficiency in the reaction process.Most chemical oscillations are studied in the aqueous solution system,whereas many photo-electrochemical reactions,widely applied in the fields of chemical engineering and new energy industries,were often constructed in organic solvent system.Different solvents would contribute to the change of migration and reactivity of intermediates almost in all elementary reactions.To construct the model oscillation reaction based on the organic photo-electrochemical reaction system,it is necessary to break through the inherent understanding of solvent effect of water in the classical oscillation reaction theory.Thereby,it will not only be challenged to regulate the reactivity and solvent compatibility of the intermediates,but also provide a new idea for the reinforcement of the organic photo-electrochemical reaction process.Aiming at the nonlinear dynamic behaviour in the common organic photo-electrochemical reaction system catalyzed by transition metal,such as DSSC and photocatalytic halogenation,the study has broken through the inherent understanding of water as solvent(constant concentration of 1)in classical chemical oscillation models,and the oscillation reaction models in organic solvent,simulating the actual organic photo-electrochemistry reaction process,were constructed by introducing a new type of ionic liquid halate to overcome the solubility bottleneck of inorganic halates in organic solvents.A series of new kinetic characteristics,different from the classical oscillation models due to the change of water' role from the constant solvent to the trace amount of reactant and the change of proton's activity,was revealed.And then new nonlinear dynamic equations were also established.The effect of the nonlinear oscillatoion behavior on the photo-electrochemical reaction process and chemical oscillation batteries was systematically investigated,thus providing a possible method to reinforce the photoelectric reaction process by regulating the dynamic oscillating behavior.Main researching results were listed as follows:(1)Aiming at Ce(?)catalyzed oxidation and halogenation process of organic acid,N-ethylpyridinium bromate-Ce(?)-MA and N-ethylpyridinium iodate-Ce(?)-MA oscillation reaction systems were successfully constructed in acetonitrile solvent by introdcing ionic liquids as the oxidants(N-ethylpyridinium bromate and N-ethylpyridinium iodate).The study showed that,two oscillation reactions both can be carried out under mild conditions and broad pH range,accompanying periodic potential oscillation and color change.In-situ spectroscopic analysis indicated that,the organic-solvent oscillation reaction still followed the classic FKN mechanism,however under the effect of enhanced activity of proton and decreased concentration of water,the dynamic parameter range of oscillation significantly changed.New nonlinear dynamic equations were established considering the influence of proton and water in acetonitrile solvent.(2)Aiming at Ru(?)catalyzed oxidation and halogenation process of organic acid,N-ethylpyridinium iodate-Ru(?)-MA oscillation reaction system was successfully constructed in acetonitrile solvent by introdcing N-ethylpyridinium iodate as the oxidant.The study showed that,the oscillation reaction can be carried out under mild condition and broad pH range of-2~6,thus may exist in practical photoelectric devices,DSSC for example.The oscillation behavior changed with the different condition of illumination because of the photosensitivity of Ru(?),and under appropriate conditions,illumination would promote the potential oscillation.The study proposed the reaction mechanism of the oscillation reaction,and revealed the effects of the enhancement of the proton activity and the decreasing concentration of water molecules on the kinetic characteristics.The work overcame the bottleneck of the iodate' low oxidation activity to construct iodate-Ru(?)-MA oscillation reaction system,which had not been reported in the aqueous solvent system.(3)Based on the study of the transition metal catalyzed oxidation and halogenation process of organic acid,the study discussed the enhancement mechanism of nonlinear oscillation behavior due to accumulation of related by-products around the photoanode of long-term working DSSC,and its effect on the device output.The study showed that,the transition metal intermediates,small organic fragments and halogen acid by-products would gradually accumulate around photoanode of DSSC after long-term working,thus forming an electrolyte system which was similar to the B-Z oscillation reaction.The existence of electrochemical oscillations could affect voltage output by more than 21%.The constructed model oscillation half-cell was combined with DSSC photoanode half-cell to form a new type of hybrid chemical oscillation cell.The electric output of the hybrid cell was a linear superposition of voltage output of DSSC photoanode and the potential oscillation of the model oscillation system,and the oscillation amplitude of the electric output was expected to be increased by further reducing the charge transmission distance.(4)Iodate-Ru(?)-MA oscillation system in organic solvent constructed in this study itself could be a chemical oscillation cell,and its power output also changed periodically.Organic-inorganic hybrid chemical cell with characteristic oscillating electric output was assembled by coupling Iodate-Ru(?)-MA oscillation system and copper' iodination based half-cell,and the amplitude of oscillating electric output accounted for more than 9.2% of average voltage output.The construction of chemical cells with characteristic nonlinear oscillation was expected to break the limitation of balance potential in traditional cells,and provide a new way to improve the output efficiency of other cell systems. |
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