Study On Layered-Hydroxide-Based Ultrathin Nanostructures And Their Electrocatalytic Performance For Hydrogen Evolution Reaction

With the rapid consumption of traditional fossil energy and the increase in pollutant emissions,energy and environmental issues have become a major challenge in this century.As a secondary energy source,hydrogen energy has the main advantages of high energy density,abundant sources,and only water as the combustion product.It is considered to be one of the best candidates to replace traditional fossil energy.The electrocatalytic water splitting for hydrogen evolution reaction(HER)is a clean and efficient process,and energy forms such as wind power and photovoltaics can be directly used for it.Therefore,the use of electrocatalytic water splitting to produce hydrogen has become a recent research hotspot.Although platinum group elements express excellent electrocatalytic hydrogen evolution activity,their high price severely limits their large-scale application.The development of electrocatalysts with both excellent performance and low price for hydrogen evolutionreaction has become an urgent problem to be solved.In recent years,two-dimensional layered materials have come into people's vision due to their excellent performance in the field of electrocatalytic hydrogen production.Among them,layered metal hydroxides(LMHs)have attracted much attention because of their high stablity in alkaline media.The metal cations and interlayer anions of the LMHs can be modulated and have rich chemical properties.Derivatives based on LMHs can also achieve functional superposition or performance enhancement.At present,the main way to improve the catalytic performance of LMHs is to make them ultrathin to obtain a high specific surface area and increase the abundant active sites generated by unsaturated coordination.Although some ultrathin LMHs have shown high activity in the field of catalysis,the precise preparation of ultrathin LMHs is still a challenge.In addition,its mechanism and efficiency in the field of HER need to be further developed.The huge potential of ultrathin LMHs prompted us to focus on its preparation and application in the field of hydrogen evolution evolution(HER).This paper focuses on the ultrathin preparation of LMHs:the preparation of ultrathin 1T-MoS2/NiS2 with molybdate intercalated nickel hydroxide as the precursor composite materials.The preparation of NiRu hydroxide ultrafine nanowires and NiVRu hydroxide ultrafine nanowires,and systematically studied the preparation mechanism and electrocatalytic hydrogen production performance of the above materials.The main research contents are as follows:(1)The 1T-MoS2/NiS2 composite was prepared by taking advantage of the interlayer anion exchangeable features of layered hydroxides and using nickel hydroxide intercalated with molybdate ions as the precursor.Among them,the metal phase 1T-MoS2,was successfully obtained with ratio up to 83%of the total MoS2 in the material.The material shows good hydrogen evolution reaction(HER)performance and stability under alkaline conditions.(2)In order to obtain a high-active site number and high-performance hydrogen evolution catalyst for electrolyzed water,a layered material with one-dimensional morphology was prepared.Using nickel foam as the substrate,the preparation of NiRu-LMH ultrafine nanowires with a width of only 2-5 nm and a length of more than 200 nm has been achieved.The number of active sites exposed to the material and the mass transfer efficiency are greatly improved.HER performance studies have shown that its performance has reached the level of commercial Pt/C catalysts.The overpotential at a current density of 10 mA cm-2 is only 16 mV,and the Tafel slope is only 40 mV dec-1.And the material has high stability in alkaline environment.(3)We designed a one-step hydrothermal method to synthesize nickel foam supported NiV double metal hydroxide ultrafine nanowires(NiVRu-LDH/NF)loaded with single atom Ru.The width is 2 nm,and with the length of more than 200 nm.The addition of V improves the conductivity of the material,and the HER activity of NiVRu-LDH/NF greatly exceeds that of commercial Pt/C,and the overpotential is oYly 6 mV when the current density is 10 mA cm-2.Its excellent HER activity mainly comes from its high specific surface area,atomically dispersed Ru and the synergistic effect of multi-metals and high electrical conductivity.Controlled experimental studies revealed that the growth of NiVRu-LDH ultrafine nanowires was carried out in the manner of Oriented attachment(OA),which further expanded the theoretical research progress of two-dimensional materials LMHs to one-dimensional morphology.