Controllable Construction And The Study Of Mixed Zn Nanosheets And Porous SnO₂ For Electrocatalytic CO₂ Reduction Reaction

The industrialization of humanity for hundreds of years has led to the sharp increase of CO₂ gas in the atmosphere,further resulting in various environmental problems and threatening the living environment of mankind.Therefore,reducing or completely balancing the CO₂ gas generated by human activities and achieving carbon neutrality offers a promising method to sustainable development.Electrocatalytic CO₂ reduction reaction（CO₂RR）which effectively convert CO₂ to valuable industrial feedback,has been widely reported owing to low energy consumption,safe and mild CO₂ conversion.At present,the development of more efficient and selective electrocatalysts provides the main ways to promote CO₂RR.Metal catalysts have been widely applied in CO₂RR due to their various morphologies and adjustable electronic valence.Electrodeposition is one of the common methods to prepare metal catalysts,and this method is rapid,mild,and controllable.The CO₂ reduction activity of the electrocatalyst can be effectively improved via special soluble substances and the change of parameters.However,the electrodeposition still has some disadvantages,such as uncontrollable morphology,the change of p H in the deposition process.In this paper,a novel solid-phase electrodeposition was proposed to prepare Zn-based nanosheets and porous SnO₂ catalyst,which is different from the traditional electrodeposition which reduce metal ions in solution.Insoluble solid such as basic zinc carbonate is used in solid-phase electrodeposition,and deposited on the surface of electrode to form catalysts with specific morphology via electrostatic force and electric field.Compared with traditional electrodeposition,solid-phase electrodeposition can control morphology and p H.The main research work of this paper is as follows:（1）Preparation of mixed Zn nanosheets:the electrodeposition process of mixed Zn nanosheets was studied by using the mixed suspension solution of basic zinc carbonate in CO₂-saturated 0.1 M or 0.5 M KHCO₃ at different potentials,and the substrate is Cu foil.The growth of mixed Zn nanosheets was observed by SEM.The morphology of mixed Zn nanosheets could be effectively controlled by adjusting the deposition potential and the amount of basic zinc carbonate.mixed Zn nanosheets exhibited Faradaic efficiency of formic acid of above 95%.In addition,the effect of basic zinc carbonate on mixed Zn nanosheets was confirmed.FTIR and XPS probed the variation of electronic state of Zn with potential and solution.We propose the machanism of electrodeposition of basic zinc carbonate on the surface of electrode.（2）Preparation of porous SnO₂:porous SnO₂ was electrodeposited in CO₂-saturated0.5 M KHCO₃ mixed tin hydroxide.The effects of tin hydroxide and deposition potential on the morphology of porous SnO₂ were studied by SEM and CO₂RR.In the process of CO₂RR to formic acid,the highest Faradaic efficiency of formic acid can reach 79%.Combined with XPS,we confirm the formation of SnO₂ instead of Sn.Therefore,we propose a mechanism of SnO₂ conversion by tin hydroxide electrodeposition.