Function-oriented Synthesis Of Nickel-based Nanomaterials And Their Energy And Environmental Applications

It is necessary to develop the clean renewable energy due to the excessive consumption of traditional fossil fuels and the environmental problems with the rapid development of the moden society.Hydrogen,as one of substitutes of the fossil fuels,has received wide attention in the past decades.Considering with the environmental friendliness,water-electrolysis is the best way to produce the hydrogen gas by using the electrocatalysts.Therefore,in order to improve the efficiency and reduce the cost,we need to develop the electrocatalysts with low overpotential and good stability.In industrial water electrolysis,it is often conducted in alkaline media for higher stability of electrode materials.However,the kinetics of hydrogen evolution reaction in alkaline is relatively slow than that in acid because the low concentration of protons in alkaline medium.Therefore,developing the electrocatalyst which has the great hydrogen evolution reaction(HER)performance in alkaline medium has become a research hotspot.In this paper,different electrocatalysts had been prepared by combining the nickel-based substrate and the molybdenum disulfide.The double active sites accelerated the alkaline hydrogen evolution reaction rate,and further enhance the electrochemical hydrogen evolution performance in an alkaline environment through its electronic structure adjustment.On the other hand,electromagnetic wave devices have been widely used in various fields and while bringing the great convenience,they have also brought about increasingly serious electromagnetic interference problems.In order to reduce the pollution caused by the harmful electromagnetic waves,it is necessary to develop materials with high microwave absorption efficiency.So,here we improved the conductivity of the nickel-based materials by vulcanization,and obtained the excellent microwave absorbing and electromagnetic shielding properties.The researches in this paper are as follows:(1)Three different heterostructure samples of NiS/MoS2,NiSe/MoS2 and NiSe2/MoS2 were prepared successfully.Their hydrogen evolution reaction performance in alkaline medium had been tested,compared and analyzed.The sample,NiS/MoS2,had the best performance among the three due to its highest activity for Volmer step:an overpotential of only 174 mV at a current density of 10 mA/cm2,a Tafel slope of 70.2 mV/dec,and good stability.(2)Based on the first part,we can further adjust the reaction rate by element doping.Different proportions of V-doped Ni-based/MoS2 heterostructure samples were prepared successfully by changing the ratio of nickel and vanadium in the reactants through a hydrothermal method.After testing and comparing the hydrogen evolution reaction performance in alkaline medium,the sample,whose ratio of nickel and vanadium is 3 to ls had the best performance:an over:potential of only 173.6 mV at a current density of 10 mA/cm2 and a Tafel slope of 92 mV/dec.Moreover,the reasons for the performance improvement were obtained.(3)The NiCO2S4 sample was successfully prepared.With its high conductivity,significant dielectric loss was obtained in the microwave range,and when the load was only 20 wt%after the optimization,the reflection loss of 49.1 dB could be achieved.Whafs more,the NiCO2S4 sample also had the excellent electromagnetic shielding properties.50 wt%NCS composite material can obtain higher than 55 dB electromagnetic shielding properties at X band.