The Preparation Of Nickel Selenide-based Composite Materials And Their Research On Electrochemical Water Splitting

Energy is becoming increasingly scarce in the modern era.Hydrogen is known as the"ultimate energy source"for human beings because of its high energy and zero pollution.Electrochemical decomposition of water is an effective method of hydrogen production.Electrochemical decomposition of water includes two half-reactions:The hydrogen evolution?HER?and oxygen evolution?OER?reactions are very important for the overall efficiency of electrochemical decomposition of water,so the development of efficient HER and OER catalysts is imminent.In recent years,studies have found that noble metal catalysts have high catalytic activity for HER and OER,but they cannot be used on a large scale because of their high cost and sparse reserves.Transition metal compounds have become catalysts for replacing noble metals,and nickel selenide has also been widely used for catalytic performance of HER and OER,and is dedicated to reducing the driving voltage of electrolyzed water.However,studies have shown that a single compound can not meet the need of catalytic activity.On this basis,we have studied nickel selenide-based composites,which show high catalytic activity and stability..The main contents of this thesis are as follows:1)Ni0.85Se nanoparticle was synthesized by hydrothermal method,and ethylenediamine-modified nitrogen-doped graphite oxide was used as conductive carrier.Ni_0.85Se nanoparticles were uniformly coated on nitrogen-doped graphite oxide to form Ni_0.85Se/NGO composites.It is found that Ni_0.85Se/NGO exhibits much higher electrochemical hydrogen evolution performance than Ni0.85Se due to the large electrochemical activity of highly dispersed nanoparticles.2)NiSe₂ nanorods were synthesized by solvothermal method using Na₂SeO₃ as selenium source and Ni?NO₃?₂·6H₂O as Ni source,followed by coating of rod-shaped NiSe₂ with carbon.The MoS₂ nanosheets were uniformly loaded on NiSe₂ rods to fabricate MoS₂/NiSe₂@C composites with money-string-like morphology.The introduction of carbon promoted electron transport,and the rod-like NiSe₂ structure provided a good dispersion carrier for MoS₂ nanosheets,exposing more active sites and improving the performance of electrochemical hydrogen evolution.3)Based on the original single metal selenide,the Co,Ni bimetallic selenide catalyst was constructed,at the same time,a copper nanowire array?CNW?with good conductivity was selected as the support.Selectivities of Ni_xCo_1-x percursor/CNW with different molar ratios were subsequently obtained by hydrothermal method to obtain the final Ni_xCo_1-xSe₂/CNW.The selenized material has more Ni and Co valence states,which increase the active sites of the catalyst.At the same time,the introduction of the copper nanowire array substrate increases the conductivity of the composite material,and the synergistic effect between the bimetallics makes it possible to exhibit high electrochemical performance oxygen catalytic activity and stability.