Preparation Of Iron Selenide-based Nanomaterials And The Study Of Electrochemical Performance

With the rapid development of global industry,people's demand for energy consumption resources is increasing.Traditional fossil fuels and other resources are gradually exhausted,and social concerns about environmental issues are also warming up.The development and utilization of renewable energy such as wind energy,tidal energy and clean energy are becoming the focus of extensive research all over the world.However,due to the limitation of existing energy storage and conversion technology,the application efficiency of green energy is low,which is far from meeting the requirements of traditional energy supply equipment.Secondary batteries,such as sodium ion batteries,can overcome the obstacles of energy storage because of their rich resources,low cost and green safety.At the same time,as a typical energy conversion technology,electrocatalytic hydrogen production has the advantages of low cost and pollution-free,which conforms to the sustainable development strategy and is the main direction of new energy development.The selection and preparation of electrode materials are particularly important for both new energy storage and electrocatalytic hydrogen production.Transition metal selenides are typical electrodes with excellent photoelectric properties,rich redox state and low cost.In this paper,FeSe2 nanosheets and FeSe2/MoSe2 composite nanomaterials were prepared by solvothermal methods,and their sodium ion storage and electrocatalytic hydrogen production properties were studied respectively.FeSe2 nanomaterials with two-dimensional sheet structur can shorten the ion migration path and improve the conductivity.At the same time,ether-based electrolyte can also optimize the charging and discharging stability of sodium ion batteries.The synthesis conditions of FeSe2 nanosheets were summarized by one-step hydrothermal method by adjusting the reaction temperature,time and the amount of iron precursor.It was applied to sodium ion batteries.The electrolyte dissolved in propylene carbonate(PC)/vinyl fluoride carbonate(FEC)with NaClO4 was compared with the electrolyte dissolved in diethylene glycol dimethyl ether(DEGDME)with NaCF3SO3.The performance of FeSe2 nanosheets was different At the current density of 0.5 A g-1,the discharge specific capacities of the two electrolytes at steady-state stage are 470 mAh g-1 and 535 mAh g-1,respectively.Ether-based electrolyte has excellent performance in capacity and stability.It does not affect the intermediate of transition metal selenides during charging and discharging.These characteristics ensure excellent performance of sodium ion batteries.The existence of heterostructures can improve the efficiency of electron-hole separation to obtain high performance catalysts.Based on the preparation of the aforementioned FeSe2 materials,Na2MoO4 was added in the hydrothermal process to synthesize FeSe2/MoSe2 and grow on carbon paper in situ.Finally,FeSe2/MoSe2@CP nanomaterials were obtained.Catalysts with different composition were prepared by adjusting the feed ratio of iron and molybdenum precursors,and their hydrogen evolution activities were investigated in detail.The overpotential of the optimized FeSe2/MoSe2 catalyst is 86.9 mV at 10 mA g-1 current density in acidic solution,and the Tafel slope is 57.7 mV dec-1.In addition to the synergistic effect between different components,the presence of heterostructures accelerates the electron transfer rate,which makes the composite exhibit better hydrogen evolution performance than pure phase FeSe2 or MoSe2.