Co/Fe-doped MoS₂ Nanosheets For Enhancing Electrocatalytic Oxygen Evolution

As global energy demand continues to grow,the consumption of fossil fuels,become more and more severe,which fastly exacerbates the greenhouse effect.Therefore,the development of clean and renewable energy attracts special attention.Among many new energy sources that can be developed,hydrogen energy is considered to be an ideal substitute for fossil fuels.In terms of hydrogen production technology,production of hydrogen through electrochemical water splitting can achieve efficient conversion between electrical energy and chemical energy,and is considered to be a hydrogen production method with great development prospects.The oxygen evolution reaction（OER）of the anode and the hydrogen evolution reaction（HER）of the cathode are the core reactions of electrolyzed water.Among them,OER is a bottleneck for the development of electrolyzed water because it involves multiple electron transfer and slow kinetics.Selecting an appropriate OER catalyst to accelerate the OER reaction process and reduce the electrical energy required for electrolyzed water is an effective way to break through the bottleneck.Currently,iridium oxide（IrO₂）and ruthenium oxide（RuO₂）are commonly used OER catalysts,however,the high price of these precious metal-based catalysts limits the large-scale application of hydrogen production by electrolyzed water.Therefore,research and development of efficient,low-cost,stable OER catalysts is essential for the development of electrolyzed water.Among the many alternatives to precious metal catalysts,transition metal sulfides represented by two-dimensional molybdenum disulfide（MoS₂）have received extensive attention in recent years.However,the OER catalytic performance of MoS₂ nanosheets is poor,and the OER catalytic activity of two-dimensional MoS₂ nanosheets can be improved by chemical doping and modification.In this thesis,a series of non-precious metal（Co,Fe）doped MoS₂-based OER catalysts were prepared by microwave hydrothermal method,and the OER catalytic properties of these materials were studied in depth.The main research contents are as follows:1.Using pure ammonium tetrathiomolybdate（（NH₄）₂MoS₄）as precursor,a pure MoS₂ nanosheet was synthesized in one step,and the OER catalytic performance of the nanosheet was tested.The results showed that the pure MoS₂nanosheet was at current density.The corresponding overpotential at 10 mA cm^-2 is 366 mV.Through structural characterization and electrochemical performance studies,it was found that the poor OER catalytic properties of the material can be attributed to the less active sites of MoS₂ nanosheets and poor conductivity.2.Prepare MoS₂ nanosheets with different Co doping amounts and test the OER catalytic properties of these materials.The results show that when the molar ratio of MoS₂ and Co is 10:1,at current density is 10 mA cm^-2 in 1 M KOH electrolyte,the overpotential at is 255 mV and the material has a Tafel slope as low as 50.6 mV dec^-1.It is indicated that the doping of Co can effectively improve the OER catalytic performance of MoS₂.3.The MoS₂ nanosheets with different Fe doping amount were prepared.The effects of Fe doping amount on the morphology and structure of MoS₂ were studied.The OER catalytic properties of these materials were tested.The results show that when the molar ratio of MoS₂ to Fe at 10:1,the OER catalytic activity of the Fe-doped MoS₂ nanosheets was significantly improved.The overpotential at a current density of 10 mA cm^-2 was 253 mV and the Tafel slope was 55.3mV dec^-1.Further study of its catalytic mechanism found that the doping of Fe effectively improved the conductivity of MoS₂.