Construction Of Manganese Sulfide-Based Composite Nanocrystals And Their Electrochemical Properties

In recent years,environmental pollution,global warming and energy crisis caused by fossil fuel combustion have become the focus of attention in the world.Therefore,the search for clean and renewable energy becomes particularly important.Hydrogen?H₂?has the highest energy density of all chemical fuels and zero greenhouse gas emissions.It is also considered to be the ideal energy carrier for the future,but hydrogen also needs to be prepared by certain methods.The production of hydrogen by electrolyzed water has the advantages of low cost,and high purity of the prepared hydrogen,etc.,so it has attracted much attention.However,the energy conversion efficiency of commercial electrolyzed water systems is about 56-73%.In order to solve this problem,we must choose a suitable catalyst to improve the energy conversion efficiency.At present,precious metal catalysts are still the most effective catalysts for HER,but their scarce earth reserves and extremely high cost make it impossible for large-scale applications.Therefore,it is very important for the hydrogen evolution reaction?HER?to find low-cost and high-efficiency hydrogen-producing non-noble metal electrocatalysts.Mn-based chalcogenide semiconductor nanocrystals have many excellent properties.Studies have found that MnS can be used as an anode material for lithium-ion batteries.The composite material formed with reduced graphene oxide can be used as a supercapacitor,so MnS exhibits good electrochemical properties.Based on the above research background,we explored the electrocatalytic performance of wurtzite MnS nanorods.In this paper,we successfully synthesized a wurtzite MnS nanorod with an average length of about 50 nm and an average diameter of about 20 nm,Au modification to form MnS@Au nanorods.MnS nanorods were combined with reduced graphene oxide and commercial C to form MnS@rGO nanorods and MnS@C nanorods,and MnS@Au nanorods were also combined with reduced graphene oxide and commercial C to form MnS@Au@rGO nanorods,MnS@Au@C nanorods.Their electrocatalytic activity was tested in a three-electrode system with a scan rate of 5 mV s^-1 in 0.5 M H₂SO₄ solution.When the current density is 10 mA cm^-2,the overpotential of the MnS@Au@rGO electrode is the lowest,and its electrode overpotential is 478 mV.Similarly,under the same current density,MnS@Au@C has lower electrode overpotential than MnS@C,MnS@Au@C overpotential is 534 mV.The results of electrochemical experiments show that Au modification enhances the intrinsic activity of active sites,improves electrical conductivity,and reduces the reaction energy barrier.Therefore,Au modification is an effective strategy to improve the catalytic performance of MnS nanorods.Heterostructure nanocrystals can bring together the advantages of different components,so that its performance tends to be better than the performance of a single component,so it has excellent optical,electrical,magnetic and catalytic properties.Recently,heterostructure catalysts have also shown extraordinary catalytic performance in terms of electrochemical water splitting.Therefore,we successfully prepared MnS/PbS core/shell nanorods by cation exchange,and controlled the thickness of the nanorod shell by controlling the reaction time,which laid the foundation for the future study of its electrochemical properties.