| As the consumption of fossil energy,the atmospheric environment is being seriously polluted,and the greenhouse effect caused by carbon dioxide is gradually increasing.New sustainable clean energy is attracting attention.Among many clean energy sources,hydrogen energy has attracted extensive attentions due to its high combustion value,high energy density,and no harm to combustion products.The main production mode to produce hydrogen is from oil and natural gas reforming,which will produce a large amount of toxic and harmful gases.Electrocatalytic hydrogen production from water has been widely concerned because of its high purity of hydrogen and the fact that the product is only hydrogen and oxygen,which is environmentally friendly.Now,platinum is widely recognized as one of the highest hydrogen efficiency electrocatalyst in catalytic electrolysis.However,due to the high price of platinum and the scarcity of crustal reserves,it cannot be applied on a large scale.In order to increase the utilization rate of platinum and reduce the amount thereof,a bimetallic alloy electrocatalyst is often prepared using platinum and transition metal element nickel.At the same time,in order to maximize the utilization of platinum atoms,nanomaterials have become a universal option.However,the morphology and size of nanomaterials have a major impact on the electrocatalytic efficiency.At the same time,the evolution of the electrocatalytic sites of nanomaterials in the catalytic process has not been clearly recognized.Therefore,in this paper,we use platinum-nickel binary alloy nanowires as research materials,regulate the surface morphology of nanowires and study the evolution of catalytic sites of nanowires in the catalytic process.The main research contents are as follows:First,platinum nickel nanowires were prepared by oil bath heating.In order to explore the factors affecting the surface morphology of nanowires,the effects of preparation temperature,reducing agent addition and sulfur doping on the surface morphology and electrocatalytic properties of nanowires were investigated by using control variables.It was found that when the preparation temperature was 180 ℃ and the reducing agent was added in an amount of 12 mg/mL,a nanowire with a core-shell structure and superficial surface morphology was obtained,and the nanowire had the best electrocatalytic performance.At the same time,it is found that the doping of sulfur element will greatly improve the electrocatalytic performance of platinum-nickel nanowires.Secondly,the platinum-nickel nanowires synthesized above were used to investigate the evolution of catalytically active sites during the voltammetry cycle.The evolution of catalytically active sites in nanowires with different voltammetric cycles was investigated using spherical aberration-corrected transmission electron microscopy and extended X-ray fine structure absorption spectroscopy(EXAFS).It was found that in the cyclic voltammetry test,the nickel element in the platinum-nickel nanowire was gradually oxidized and migrated to the surface of the nanowire,eventually forming a thick NiOOH layer on the surface of the nanowire,blocking electron transport and hindering adsorption.The hydrogen at the site is desorbed,thereby reducing the electrocatalytic efficiency of the platinum-nickel nanowires.Finally,this paper designs and manufactures an electrothermal sample holder system for liquid environment TEM,which uses the electrochemical detection/heating chip and the designed water inlet and outlet to realize the in-situ nano-sample morphology observation and characterization in multi-field loading and liquid environment.In order to further explore in situ the platinum-nickel nanowires provide an equipment basis for the evolution of catalytically active sites during the catalytic process. |
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