| With the development of the industry,the massive usages of fossil fuels have triggered a series of global environmental degradation,greenhouse effect,and energy shortage.At the context,hydrogen,as a clean and efficient renewable secondary-energy source,has become one of the important alternatives to fossil fuels,showing a good prospect of application.At present,storing hydrogen energy in liquid fuel with the form of chemical energy,which is easy to store and transport,is a main method for the development and utilization of hydrogen.At present,catalysts for electrocatalytic hydrogen production mainly have some defects such as poor stability,complicated products,and low conversion rate.Although the catalysts based on transition metal oxides,sulfides,nitrides,and organometallic framework compounds have made considerable progress.However,the understanding of transition metal single-component catalysts and reaction mechanisms is still under investigation.In recent years,the three-dimensional structural materials,such as the nanoporous metal materials prepared by the dealloying method,have attracted wide attention of researchers and provided new ideas for the design and development of catalysts.The nanoporous metals have a continuous,quasi-periodic and three-dimensional nanoporous network structure with good design-ability.The nanoporous metals can be characterized by its low coordination table interface structure,electronic localization effect and large specific surface area.With these properties,the nanoporous metals can balance the relationship between electrons and mass transfer,showing high efficiency and high activity.At the same time,based on this uniform and stable three-dimensional structure,surface defects,different crystal faces and catalytic sites dispersed on the ligaments,the nanoporous metals are more easier to maintain catalytic stability,which are applied in the fields of energy storage,catalysis,and biosensors and so on.In this paper,the nanoporous nickel films have been prepared by magnetron sputtering and dealloying,then been applied in the hydrazine electrodecomposition,and also the molecular mechanism of the electrocatalytic decomposition of hydrazine on Ni(111)surface has been explored by density functional theory(DFT).At last,the composite electrode of Pt@nanoporous nickel is prepared on the basis of nanoporous nickel substrate,and is applied to the reaction of electrolysis of water to hydrogen.The specific research contents is as follows:(1)We prepared alloy precursors of Ni35A165,Ni5OAl5O and Ni4OAl6O with different element ratios by magnetron sputtering.Then,nanoporous nickel film electrodes with different pore were prepared by chemical etching.Through various electrochemical tests on nanoporous nickel electrodes and analysis of gas products,we studied the catalytic activity and selectivity of nanoporous nickel electrodes for hydrazine electrodecomposition,and selected the nanoporous nickel electrode with best catalytic performance.(2)We calculated the catalytic decomposition of N2H4 molecules on the Ni(111)plane by density functional theory,and analyzed the N2H4 molecules and their intermediates N2H5*,N2H2*,N2H3*,NH2*and NH3*molecules in Ni(111)The change of Gibbs free energy on the surface,compare and analyze the energy change of the voltage,and obtain a clear dehydrogenation reaction path and a method for suppressing the formation of by-products.By adding voltage,the production of ammonia will be reduced.The reaction mechanism of hydrazine hydrate on the Ni(111)surface was studied.(3)Using nanoporous nickel as the substrate,a composite electrode of Pt@nanoporous nickel was prepared,and its surface structure was characterized and analyzed by physical analysis.Hydrogen evolution reaction test was carried out on electrode materials with different parameters.We studied the catalytic activity and selectivity of Pt@nanoporous nickel electrodes for hydrogen evolution reaction,and selected the electrode materials with the best catalytic performance. |
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