Design Of Transition Metal Sulfide Functional Materials And Their Study On Electrocatalytic Performances

With the development of society,energy and environmental problems are becoming more and more serious.The burning of a large amount of traditional fossil fuels has caused serious energy crisis and environmental pollution,which has attracted widespread attention.Therefore,the development of sustainable,clean,efficient energy and conversion technology is imperative,because energy is an indispensable material basis for the development of human society.Now,electrocatalysis has become a research focus because of simple operation,clean process,and high conversion efficiency.The electrocatalysis method to prepare hydrogen and ammonia meets the development requirements of human society for energy?sustainable development and environmental friendliness?.Hydrogen is considered to be the cleanest energy because its only combustion product is water,and no other by-products so it achieves zero pollution.Ammonia is one of the most important industrial chemicals,and it is widely used in agriculture and other fields.As we all know,for electrocatalysis,electrocatalyst materials are undoubtedly the top priority.Among them,noble metal-based catalysts,such as Ru,Ir,Pt,Pd,etc.,have very excellent catalytic performance,but their high price limits their widely application.Therefore,it is a trend to design and develop catalysts with low precious metal content,especially non-precious metal catalysts.Based on the above design principles,this paper is focus on the design and development of several high-efficiency non-noble metal catalysts around the hydrothermal method,CVD method,etc.,to achieve the efficient conversion of energy in electrocatalytic water splitting and nitrogen reduction.This work is described as follows:1?Anchored CoS₂ nanodots into heteroatom-doped carbon layer?CoS₂@HADC?via a biomimetic strategy: Boosting the OER performance.Numerous CoS₂ nanodots and heteroatoms rich in N and S were in situ hybridized into the carbon layer in a homogeneously dispersed manner provided abundant active sites,boosting electrochemical performances for OER in basic electrolyte.The optimized hybrid CoS₂@HADC achieved the lowest overpotential of 226 m V at 10 m A cm^-2,the OER performance is greatly superior to Co-based catalysts previously reported.In addition,the reported method is universal and scalable for other transition metal sulfides and carbon substrates.2?This work offers MoS₂@Ni0.96 S heterojunction hybrids as efficient bifunctional electrocatalyst,which are achieved by a facile hydrothermal and annealing strategy.Benefitted from rich defects from non-stoichiometric Ni0.96 S nanocrystals and abundant catalytically active edges provided by ultrathin MoS₂ nanosheets,as well as intimate heterojunction interfaces between Ni0.96 S and MoS₂,the optimal hybrid exhibit superior electrocatalytic activities in alkaline electrolyte with HER overpotential of 104 m V at 10 m A cm^-2 and OER overpotential of 266 m V at 20 m A cm^-2.In addition,MoS₂@Ni0.96 S heterojunction hybrids have superior durability in alkaline electrolyte.3?Ti³⁺-TiO₂-x/TM was prepared by wet-chemical oxidation of TM using H₂O₂ as an oxidant.An effective strategy to improve the TiO₂ NRR activity is usually chemical doping with heteroatoms,including non-metals and metals.Now,without introducing impure elements into TiO₂,Ti³⁺ self-doping can increase the electrical conductivity and accelerate the transfer of electrons and holes.When tested in 0.1 M Na₂SO₄,such catalyst offers a high FE of 14.62% with a large NH3 yield of 3.51 x 10–11 mol s–1 cm–2 at –0.55 V vs.the reversible hydrogen electrode?RHE?,superior to the behaviors of most reported Ti-based NRR electrocatalysts at ambient conditions.4?FeNi₂S₄ nanosheet arrays was growth on NF?FeNi₂S₄/NF?as efficient OER electrocatalyst.The FeNi₂S₄/NF achieved the lowest overpotential of 230 m V at 50 m A cm^-2 in 1.0 M KOH.The experiments were mainly analyzed the changes of the material during the OER process through Raman,SEM and other characterizations,and proved that the FeNi₂S₄ became Ni Fe O?OH?after electrochemical testing in this chapter.These results indicate that the FeNi₂S₄/NF is a kind of precatalyst with excellent performance.