| The impending global energy crisis caused by the heavy reliance upon traditional fossil fuels encourages researchers to search for possible renewable energy strategies.Fuel cells and hydrogen,due to their favorable characteristics such as clean,high efficiency and renewable,gradually become research hotspots i n the new energy industry.Currently,noble metals,such as Pt and Au,have been demonstrated as the state-of-the-art catalysts.But scarcity and high cost of these precious metals hinder their application on a large scale.A recent improvement in the cata lysts has been the discovery of cheap,earth-abundant catalysts,especially transition metal oxides,transition metal dichalcogenides（TMDs）and transition metal phosphides（TMPs）.In this thesis,several kinds of catalysts based on transition metal compou nds were designed and synthesized,and their applications in electrochemical catalysis were also investigated.Three-dimensional structure nanocomposites of hollow porous Co3O4nanododecahedras anchored on carbon nanotubes（3D Co3O4-HPND/CNTs）was prepared via direct calcination of metal-organic framework-67 in-situ formed on carbon nanotubes,and their electrocatalytic properties towards the glucose oxidation were investigated;3D porous layered composite of transition metal dichalcogenides Mo-CoSe2 nanosheets stacking-grows on Ni foam（Mo-CoSe2 NS@NF）via electrodeposition,hydrothermal and thermal selenization,and the electrocatalytic performance towards HER and OER were surveyed;Ni foam with vertical bimetallic phosphides nanoarrays were synthesized via topological transformation,and the electrocatalytic properties were surveyed in alkaline media.The particular work s are detailed as follows:（1）Firstly,PTCA-CNTswere fabricated by assembling CO2+on the surface of CNTs functionalized with 3,4,9,10-perylene tetracarboxylic acid（PTCA）viaπ-πstacking.Then,by combining with imidazolate-derived ligands,ZIF-67 in-situ grew on the surface of PTCA-CNTs to obtain ZIF-67@CNTs.Finally,3D hollow porous Co3O4dodecahedron and CNTs composite material（3D Co3O4-HPND/CNTs）was obtained via direct calcination of ZIF-67@CNTs.The as-prepared samples are well characterized by scanning electron microscopy（SEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray diffraction（XRD）and Brunauer-Emmett-Teller（BET）surface area.Electrochemical measurements were performed in a three-electrode system by linear sweep voltammetry（LSV）,cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）.Results reveal that,when worked as an anode of a glucose fuel cell,a maximum power density of 210μW cm-2 at 0.15 V can be obtained,and the open circuit potential is 0.68V.（2）Molybdenum-doped CoSe2 nanosheets self-standing on Ni foam composites（Mo-CoSe2 NS@NF）had been successfully synthesized via electrodeposition,hydrothermal,and thermal selenization methods.The morphological features of the samples are well characterized by SEM,TEM,EDS,XRD and XPS.Electrochemical measurements were performed in a three-electrode system by LSV,CV and EIS.The results indicate that the Mo-CoSe2 NS@NF electrocatalyst possesses excellent activities in alkaline solution with overpotential of 89 mV and 234 mV to reach the current densities of 10 mA cm-2 for HER and OER,and the corresponding Tafel slopes are 69 mV dec-1 and 58.8 mV dec-1,respectively.Moreover,the two-electrode alkaline water electrolyzer affords water-splitting current of 10 mA cm-2 at a cell voltage of1.56 V with excellent stability.（3）The self-standing ternary FeCoP nanowire arrays on Ni foam（FeCoP@NF）was prepared by hydrothermal and phosphorization.After measured by physical characterization methods of SEM,TEM,EDS,XRD,XPS,and electrochemical measurements of LSV,CV and EIS,it proved that 300 oC is the optimal preparation temperature.FeCoP@NF-300 possesses an overpotential of only 94 mV to drive 10mA cm-2 and the Tafel slope is 60.4 mV dec-1.Besides,it shows negligible decay during continuous hydrogen evolution of 1000 cycles,indicating the high HER activity and long-term stability. |
