Structure Design, Synthesis And Application Of Multi-Functional Catalysts

The new energy devices and materials are under hot research and being developed rapidly due to outstanding performance in relevant aspects.The fields of new energy materials and devices include super capacitors,solar cells,electrocatalytic water decomposition and many other fields.In the large family of solar cells,TiO₂ dye-sensitized solar cells?DSSCs?are one of the most gifted new energy devices because of its high photoelectric conversion efficiency?PCE?,low cost of materials and simple assembly steps.Among them,DSSC's counter electrode is the important to its outstanding photoelectric conversion presentation,and it is generally believed that precious metal Pt has excellent performance as the ideal material of counter electrode.However,precious metals are rare and expensive,which are not fit for mass manufacture.This will seriously hinder the development of counter electrode and DSSC.Therefore,we are making efforts to develop materials that can replace precious metals Pt;the supercapacitor not only has the same high discharge power as the traditional capacitor,but also has the same ability to store charge as the battery,which has involved more care of academics.In general,super capacitors can be divided into two types by energy storage:electric double-layer capacitors?EDLC?and pseudo capacitors?pseudo capacitors generated by fast and reversible chemical absorption desorption or oxidation-reduction reactions?.Here,no matter what type of super capacitors,their working electrodes play a decisive role.Therefore,the electrochemical performance of the functional materials loaded on the working electrode is the central part of the super capacitor to promote the energy storage performance;the electrocatalytic hydrogen evolution reaction is one of the electrocatalytic water decomposition reactions,which has a good scene of progress.It can be split into two types:acidic environment and alkaline.In the electrocatalytic hydrogen evolution reaction,the catalytic material supported by the working electrode is an important part of hydrogen evolution,and the catalytic ability of the material directly determines the gas evolution rate.Recently,nanocomposites,especially transition metal sulfides,metal oxides and heteroatom doped composites on account of carbon materials,have involved wide focus because of their outstanding electrochemical possessions and have been extensively applied to many fields.Ni₃S₂ as a transition metal sulfide has achieved good performance in many fields.Among them,the hollow sandwich composite?NHC/Ni₃S₂/RGO?composed of nitrogen doped hollow carbon spheres?NHC?,nickel disulfide sheets?Ni₃S₂?and conductive graphene oxide protective layers?RGO?,it has good electrochemical and related properties in dye-sensitized solar cells,supercapacitors and acid HER;As a typical metal oxide,Fe₃O₄ has a certain photoelectric performance.As a composite of metal oxide and carbon material,Fe₃O₄ and N-rGO modified by nitrogen element show excellent photoelectric performance in dye-sensitized solar cell;Nitrogen doped core-shell carbon spheres?N-CCS?,as a complex of heteroatom doped carbon materials,it is applied in the conflicting electrodes of DSSC.The detailed research substance are as follows:?1?A novel metal-free conductive catalyst is designed based on N-doped core-shell carbon spheres?N-CCS?with rich active sites.Furthermore,the doping of N atoms activated the fully interconnected mesoporous basal planes of carbon spheres.Corresponding electrochemistry?Cyclic voltammetry,electrochemical impedance spectroscopy,and Tafel polarization measurements?test discovered the excellent electrocatalytic activities in the I^-/I₃^-redox reaction of dye-sensitized solar cells?DSSCs?,suggesting to result from the improvement of the surface electronic properties of CCS.DSSCs with N-CCS as the counter electrode?CE?achieve power conversion efficiency?PCE?of 7.89%,higher than to Pt's value?7.48%?in the same test environment,demonstrating as a hopeful catalyst for low-cost DSSCs,and confirmed the original idea.?2?Inspired by the truth that the hierarchy structure nanocomposites can exhibit superior electrochemical performance because such structure can provide more electron transfer routes,here we reported the preparation of Fe₃O₄@N-rGO nanocomposites which can match this point.The power conversion efficiency?PCE?of the cell with Fe₃O₄ nanoparticle as counter electrode is 6.85%while PCE for the cell with Fe₃O₄@N-rGO nanocomposites as counter electrode shows great enhancement,and the highest value is up to 8.18%,even higher than Pt's efficiency?7.17%?in the same environment.The great performance can be ascribed to the hierarchy structure of N-rGO and the excellent conductivity of Fe₃O₄ to achieve dual-functional structure optimization.The 2D hierarchy structure N-rGO film in the hybrids plays two important roles:the more active sites for dispersed Fe₃O₄ nanoparticles promoting catalytic efficiency and the higher electrical conducting structure for quickly charge transfer.The 2D hierarchy structure N-rGO film will be a great help for Fe₃O₄ particles as CE application in DSSCs;?3?At present,the catalytic materials in many catalytic fields have single characteristics,so it is difficult to apply in other fields and form a"monotonous application"situation.In order to apply one material more reasonably and economically,we have studied the commonality of material performance requirements in many catalytic fields,and legitimately intended multi-functional materials that can be used in numerous catalytic fields.This work intelligences a hollow sandwich compound consisting of nitrogen-doped hollow carbon spheres,flake nickel disulfide and reduced graphene oxide conductive protective layer.The large specific surface area contributes to the rapid ion transport in electrochemical reaction,and the hollow structure provides space for ion storage.The DSSC based on NHC/Ni₃S₂/RGO counter electrode obtained the power conversion efficiency?PCE?of 9.03%,the specific capacitance of the supercapacitor achieves 990.6 mF g^-1,and For HER,the current density of10 mA cm^-2 can be achieved with only-142 mV overpotential when the composite is used and it also has a small Tafel slope(98.1 mV dec^-1)in 0.5 M H₂SO₄ solution.It delivers a support for catalysis and energy storage and energy conversion,and realizes"one material for multiple purposes";...