| Under the background of the national"double carbon"strategy,academia and industry have paid much attention to the preparation and application of green hydrogen.Electrocatalytic technology can realize the mutual conversion of chemical energy and electrical energy,which involves several electrochemical processes such as Hydrogen Evolution Reaction（HER）,Oxygen Evolution Reaction（OER）,and Oxygen Reduction Reaction（ORR）,which is the key technology of green hydrogen preparation and application.Among many electrocatalytic materials,noble metal catalysts are widely used because of their excellent activity and stability.However,precious metal is scarce and expensive,which restricts its large-scale application.Herein,the development of high-performance low-load precious metal electrocatalysts has important research significance and application value.This thesis focuses on the preparation and performance of low-load precious metal（Pt,Ru）electrocatalysts.A series of catalysts with different structures were prepared,and the structures of the catalysts were characterized by modern microscopic testing methods,and the key factors affecting the activity of the catalysts were clarified.By regulating the electronic structure and active site of the electrocatalyst,the design and preparation of a new type of electrocatalyst with enhanced catalytic activity and good stability.The main research content of this thesis includes:（1）Ruthenium-doped cobalt phosphide nanosheets（Ru-Co P/CC）were prepared on carbon cloth by hydrothermal and chemical vapor phosphating.The structure and electrochemical properties of the catalyst were studied.It was found that Ru doping optimized the local electron distribution on the Co P surface,induced electron deviation from Ru to Co P,promoted the transformation of Co ions into electron-rich states,and then led to the reconstruction of the electron coordination environment of Co-P,and improved the ability of electrocatalytic hydrogen evolution.By further optimizing Ru content,it is found that Ru-Co P/CC-2 electrocatalyst has the optimal activity,which can reach 10 m A cm-2 current density at a low overpotential of 45 m V,and can work stably at 20 m A cm-2 current density for 20 hours.This provides a new perspective and practical reference for developing and applying highly active hydrogen evolution catalysts.（2）A typical two-dimensional Mo S2 nanosheet array was selected as the modified object,and a low Ru loading Mo S2 nanosheet array（Ru-Mo S2/CC）was prepared on carbon cloth using a one-pot thermal method by anchoring Ru metal dopants with S atoms in Mo S2 crystal plane.The effects of Ru content on the morphology,composition,and HER activity of catalyst samples were studied.It was found that the overpotential of0.01-Ru-Mo S2/CC catalyst was only 169 m V when the current density of10 m A cm-2 was reached in 0.5 M H2SO4 electrolyte,and 90 m V when the current density of 10 m A cm-2 was reached in 1.0 M KOH electrolyte.And the catalyst has excellent stability in a wide p H range in the electrolyte.The low Ru load reduces the cost of the electrocatalyst,and the Ru-Mo S2/CC design increases the active site of the catalyst and improves the electrocatalytic activity.This provides a practical reference for the design and development of high-activity HER catalysts.（3）Based on the theory of cooperative electron interaction,the Ru-Ni Fe hydroxide nanosheet（Ru-Ni Fe LDH）OER electrocatalyst was designed and prepared by hydrothermal reaction.The structure and electrochemical properties of the catalyst were studied.The results showed that the active sites of Ni,Fe,and Ru species were increased,and the surface electron interaction was enhanced,so the Ru-Ni Fe LDH electrocatalyst showed excellent electrocatalytic oxygen evolution performance.By comparing and analyzing the electrocatalytic properties of different Ru contents,a current density of 50 m A cm-2 and a slope of 58m V dec-1 can be obtained at 222 m V overpotential for 10Ru-Ni Fe LDH electrocatalyst.In addition,the catalyst can work stably for 25 h at a high current density of 100 m A cm-2 without obvious attenuation.The design idea and excellent performance of Ru-Ni Fe LDH electrocatalyst lay a theoretical and technical foundation for the development of low-cost and high-performance OER electrocatalyst.（4）Pt Mn@Pt core-shell nanowires were prepared by hydrothermal method and displacement reaction using polyvinylpyrrolidone（PVP）as a dispersant and morphology control agent.The phase composition,morphology,structure,and electrochemical properties of Pt Mn@Pt core-shell nanowires were studied by various characterization methods.It was found that the Pt layer with a thickness of 1-2 nm was coated on the surface of Pt Mn nanowires.Pt Mn@Pt core-shell nanowires exhibit excellent ORR catalytic activity and electrochemical stability.The PVP concentration changes the microstructure of the nanowires and influences their catalytic activity.When the amount of PVP was 50 mg,the mass specific activity of Pt Mn@Pt core-shell nanowires was 0.409 A mg-1（@0.9V）,which was3.86 times that of commercial Pt/C.The half-wave potential of Pt Mn@Pt-P2/C is 0.928 V,which is 83 m V higher than that of 20%Pt/C（0.845 V）.The Pt layer with a thickness of 1-2 nm inhibited the dissolution of Mn,so the Pt Mn@Pt core-shell nanowire electrocatalysts showed better stability than commercial Pt/C catalysts.The strain effect of Pt Mn alloy nanowires,the electronic interaction between PVP and Pt,and the 1-2 nm thickness of the Pt layer promote the excellent ORR catalytic activity of Pt Mn@Pt-P2/C electrocatalyst.Pt Mn@Pt.The design and excellent performance of core-shell nanowire electrocatalysts provide new ideas for the design and preparation of nanowire electrocatalysts.This thesis includes 63 figures,8 tables,and 235 references... |
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