Controllable Synthesis Of Molybdenum Disulfide And Its Electrocatalytic Reduction Reaction For Small Molecules

The increasing emission of carbon dioxide into the atmosphere caused by excessive consumption of fossil fuels and industrial ammonia production have led to the greenhouse effect and global climate anomalies,which has aroused the concern of governments and scholars of all over the world.The electroreduction of carbon dioxide and nitrogen to high value-added fuels and chemicals not only can reduce the concentration of carbon dioxide in the atmosphere but also convert electrical energy into chemical energy for storage.However,the catalysts reported so far have many problems such as various by-products,poor selectivity,high onset potential,and too low current density.Therefore,developing electrocatalysts with high catalytic activity and good selectivity has become significant issue.As a kind of layered two-dimensional nanomaterials,MoS₂ has been considered as a kind of promising electrocatalysts.However,MoS₂ still suffers from low yield of C₂ products and additional use of ionic liquid when it is used as electrocatalyst for CO₂ reduction.While it shows poor electrocatalytic activity for N₂ reduction.The fabrication of dual active sites can adjust electrocatalytic activity and selectivity of MoS₂ for CO₂ reduction.N₂ molecules can be activated through defect engineering.Considering the above-mentioned facts,this dissertation focuses on the design and performance optimization of molybdenum disulfide nanomaterials.The activity and selectivity of MoS₂ for electrocatalytic reduction of CO₂ and N₂ were improved through the fabrication of composite material and defect engineering.The main research contents are as follows.?1?MoS₂ nanosheet arrays were synthesized by a facile hydrothermal route,using Mo net as substrate.TiO₂ with different thicknesses were loaded on the as-obtained MoS₂ nanosheet arrays by atomic layer deposition technique to form TiO₂/MoS₂composite.The synthesized composite material was tested for electrochemical reduction of carbon dioxide in 0.5 M KHCO₃ electrolyte.As a result,current density and Faraday efficiency of ethanol and acetic acid obtained over TiO₂/MoS₂were superior to those of pristine MoS₂.The results showed that the Ti-O-Mo bonds were formed due to the loading of TiO₂.This bond served as the dual active site for electrochemical reduction of CO₂,which effectively modulated the catalytic performance of the material and inhibited the activity of hydrogen evolution reaction,and thus improved the activity and selectivity of C₂ products?2?MoS₂ nanosheets obtained through hydrothermal method were treated through the plasma etching technique,which could increase the defect concentrations of MoS₂nanosheets.MoS₂ with defects could modulate the catalytic activity for N₂electrochemical reduction.The performance test of electrocatalytic reduction of nitrogen showed that defect-rich MoS₂ showed enhanced electrocatalytic activity,compared with original MoS₂.To be specific,defect-rich MoS₂ could electrochemically reduce N₂ to NH₃ and achieve 28.85%of FE_NH3 and 10 h stability.The performance achieved over defect-rich MoS₂ is superior to most molybdenum disulfide materials reported.