Structure Design And Alcohol Electrocatalytic Oxidation Properties Based On Novel Carbon Supports

With the increasing consumption of fossil fuels and the decreasing reserves,energy and environmental problems are becoming more and more prominent.As a new type of green energy conversion device,fuel cell is an effective choice to solve environmental pollution and energy crisis.Among the fuel cells,catalyst is one of the core components,and it is the main technical barrier for the preparation of high performance and low cost in fuel cell.The catalytic performances of the catalyst can be improved from optimizing the morphological size of precious metals and support composition.The catalysts could be malfunctioned and the catalytic performance would be negatively influenced when there is CO intermediate products present in the system.With the development of energy storage materials,the flexible development of traditional catalyst support is the future direction of fuel cells Developing foldable energy devices with robust mechanical property,portability,foldability and high electrochemical activity has received growing interests.Despite the demand,to our knowledge,there are no reports involving flexible electrodes for fuel cells.In this paper,the novel carbon materials were prepared as supporting for catalysts,which is benefit for improving the anti-toxic and electrocatalytic performance.Moreover,constructing freestanding and flexible carbon materials as support for distributing nanoparticles towards methanol oxidation.The main content in this thesis is listed in the following four aspects:?1?Hollow graphitized carbon nanocage supported Pd catalyst applied in ethanol oxidation reactionHollow graphitized carbon nanocages were developed for improving the electrocatalytic performance of Pd nanoparticles?NPs?towards ethanol oxidation.A mild method was utilized for the preparation of hollow graphitized carbon nanocages?CN?using magnesium oxide as a sacrificial template without high-temperature processing.The Pd/CN catalyst was prepared via a simple reflux procedure,and ethanol served as reductant.The CN can act as high-efficiency support for the distribution of Pd NPs.A set of characterizations,including SEM/TEM,XRD,XPS,BET,among others,were performed to confirm their morphology,composition,and structure.Pd NPs decorated on CN exhibited high catalytic performance with the current density of 2411.5 mA mg^-1 for ethanol oxidation reaction?EOR?,which is 1.84 and 4.42 times higher than reduced graphene oxide?RGO??1308.5 mA mg'?and C(545.2 mA mg^-1)as supports,respectively.Pd/CN exhibits good durability during the chronoamperometric experiments of long-term durability.The Pd/CN with excellent catalytic performance can be attributed to the CN,including the large surface area with a mesoporous hollow structure,uniform dispersion of Pd NPs,and excellent electrical conductivity.This study may offer new insights for the development of highly effective carbon-based support for applications in ethanol oxidation.?2?PdS_x/C porous nanospheres applied in ethanol oxidation reactionCarbon-supported palladium polysulphide?PdS_x/C?porous nanospheres were prepared by a facile approach to be applied to ethanol oxidation in alkaline medium.The success of this synthesis relies on the preparation of palladium/poly?3,4-ethylenedioxythiophene??Pd/PEDOT?nanospheres via the reduction of Pd2+by EDOT,followed by calcination at an elevated temperature.A set of characterizations,including SEM,TEM,HRTEM,XRD,Raman,XPS,among others,were performed to confirm their morphology,composition,and structure.The effects of calcination temperature on the structure and morphology of products were systematically investigated by compared samples obtained at different calcination temperatures.It is noteworthy to mention that the calcined product remained spherical shapes when annealed to high temperature.The PdS_x particle size distribution conforms to normal distribution with an average diameter of 2.47 ± 0.60 nm.Tiny nanoparticles are anchored on the surface of PdS_x/C porous nanospheres and distributed homogeneously.It is well known that the Pd catalyst could be malfunctioned and the catalytic performance would be negatively influenced when there is sulfur present in the system.Interestingly,unlike common sulfur-poisoned Pd catalyst,the as-prepared PdS_x/C porous nanospheres were found to show electrocatalytic activity with a value of 162.1 mA mg^-1 for ethanol oxidation in alkaline medium.In particular,the forward peak current intensity achieved 162.1 mA mg^-1 and still kept at 46.7 mA mg^-1 even after 1000 cycles.This work not only prepared a novel catalysts for ethanol oxidation,but also provided a new methods for solving the sulfur-poisoning problem for Pd catalyst in EOR.?3?Pt NPs decorated 3D macroporous Ti₃C₂ MXene Frameworks as a catalyst for high performance methanol oxidation2D Ti₃C₂ MXene sheets were processed into 3D macroporous interconnected embossed architectures?e-MXene?via monodispersed polystyrene?PS?spheres as sacrificial templates to suppress the stack together of MXene sheets,which can be used as skeletons for supporting Pt nanoparticles?Pt/e-MXene?for methanol oxidation.The e-MXene not only mantain the intrinsic properties?such as metallic conductivity,a hydrophilic surface,and good mechanical stability?but also render the new feature of high surface area.A set of characterizations,including SEM,TEM,XRD,XPS,among others,were performed to confirm their morphology,composition,and structure.When used as catalysts for methanol oxidation,the Pt/e-MXene catalysts show much improved performances compared to multilayer MXenes as supporting in terms of electrocatalytic activity and stability,as demonstrated by its peak current density of 798.7 mA mg pt-1 almost two times larger than that of Pt/MXene?398.6 mA mg Pt-1?.This work demonstrates the advantages of 3D macroporous MXene architecture on the electrochemical performance of methanol oxidation and can widen the application of MXene-based materials in the field of energy storage,catalysis,environmental,and biomedical applications.?4?Paper-based porous graphene/single-walled carbon nanotubes supported Pt nanoparticles as freestanding catalyst for electro-oxidation of methanolA freestanding 3D interconnected embossed graphene?e-RGO?-single wall carbon nanotubes?SWCNTs?paper as skeletons for supporting Pt nanoparticles?Pt/e-RGO-SWCNT?without binder,which can be used as a flexible and robust electrode for methanol oxidation.The 3D porous e-RGO was prepared by using monodispersed polystyrene?PS?spheres as sacrificial templates to suppress the re-stacking of RGO sheets.Meanwhile,the SWCNTs penetrated through the e-RGO,and thus weaved them into a scalable film to provide an integrative conductive framework.The Pt/e-RGO-SWCNT is expected to show excellent electrocatalytic activities toward MOR.A set of characterizations,including SEM/TEM,XRD,XPS,and BET,among others,were performed to confirm their morphology,composition,and structure.Benefited from their high surface area,3D porous interconnected architecture,and good electrical conductivity,the Pt/e-RGO-SWCNT catalyst exhibited much higher electrocatalytic activity and durability for methanol oxidation than Pt/e-RGO and Pt/RGO catalysts.More importantly,the Pt/e-RGO-SWCNT is demonstrated to be outstanding flexible electrocatalysts,and the electrocatalytic performances under the different distorted situation?such as folded and rolled states?are almost the same as the normal state.