Research On Interfacial Reaction Mechanism Of Metal Additives For Electrodeoxidation Of Oxide In Molten Salt

Metals play an important role in the preparation of Si materials.Common chemical vapor deposition methods and etching methods use metals as catalysts to prepare silicon nanostructures.However,these methods have many shortcomings,such as high energy consumption,gaseous precursors for difficult control and harsh experimental conditions.The etching methods has many steps and requires etching with an etchant,so the yield is low.The preparation of silicon metal by molten salt electrolysis has received extensive attention in recent years,but the mechanism of metal growth and nucleation of silicon in molten salt systems needs further study.In this paper,different metal additives and nano-silica powder are used as precursors.Through multi-factor control experiments,the characteristics of silicon nucleation,generation and morphology evolution in the process of molten salt electrolysis are systematically investigated.Nano Si material modified by metal particles was produced.The main research contents are as follows:（1）Using CaCl₂-NaCl molten salt as the high-temperature reaction medium,the Au/Si composite was prepared by molten salt electro-deoxidation at 850°C for 2.2 V after 8 h.The cathode was Au@SiO₂and Au Cl₃@SiO₂solid precursors.The study found that when Au is used as a metal additive,the main components of the product are Si and Au,but no nanowires are generated in the product;when Au Cl₃is used as a metal additive,silicon nanowires are successfully prepared.It can be seen that Au Cl₃as a gold source can be co-reduced with SiO₂,triggering the formation of liquid-phase gold-silicon alloy,and contributing to the formation of silicon nanowire morphology.At the same time,too high or too low electrolytic voltage is not conducive to the acquisition of silicon-gold composite.It can be seen that changing the electrolytic voltage has an effect on the product morphology.（2）By changing the metal additive to Ag,the best experimental conditions were explored with the research of Ag@SiO₂solid precursors,and the role of the metal additive and the interface reaction mechanism were discussed.By changing the experimental temperature,electrolytic voltage and reaction time,the preparation conditions of the Ag/Si composite were optimized,and the best reaction condition was determined to be electrolysis at 2.2 V for 8 h at 850°C.A molten salt experimental system for preparing Si nanowires is explored.The growth mechanism and interfacial reaction mechanism are discussed.In the molten salt electrolysis process of Ag@SiO₂,there are two reaction mechanisms:one is the LS growth mechanism,and the metal Ag plays an important role;the other is the tendency to generate silicon nanowires at low potential.Below the eutectic point of Ag-Si,silicon nanowires are observed in the product morphology,but there are still granular products;above the eutectic point,the main components of the electrolytic product are silicon nanowires,which proves that the former is the main mechanism.