The Modification Of Biomass-based Carbon Materials And Their Application Research In Electric Catalytic System

Currently, the worsening environment and energy crisis have urged extensiveresearch and development of green and sustainable energy systems. Direct methanolfuel cell (DMFC) is a extensive researching technique due to the high specific energy,environmentally friendly and portable device. However, there are many technicalchallenges for the commercialization of DMFC that remain unsolved, including lowchemical rates, methanol crossover, expensive catalyst and catalyst poisoning.To date platinum and platinum based catalysts are still the most dominantcatalysts for both anode and cathode in DMFC due to its superior catalytic activityand long term operation stability. However, Pt, a rare and expensive novel metal innature severely limits the broad applications of fuel cells. Two main approaches toreduce the cost of catalysts are currently pursued:1) to decrease the loadings ofprecious platinum metal catalysts and higher utilization of Pt particles and2) toexplore non-noble metal or non-metal catalysts. Carbon is an ideal material forsupporting nano-sized metallic particles in fuel cell applications. The carbon supportshave obvious influence on the distribution, catalysis and durability of Pt-basedparticles. They not only can improve the utilization of Pt precious metal, but also canact as non-metal cathode catalysts after a certain surface modification. So people paymore and more attention to the research of carbon support materials.In recent years, biomass-based carbon materials have found a large number ofapplications in different domains ranging from environmental science, tosupercapacitor, energy storage and electrical catalysis fields. Biomass-based carbonmaterials have a larger specific surface area and specific pore structure compared toconventional carbon black (Vulcan XC-72), these are beneficial to improve thedispersion of metal nanoparticle catalysts and to promote electron transfer during theelectrochemical reaction process. They are promising applications in electrochemistryfield. However, most of biomass-based carbon materials were used inadsorption-related fields, only a handful of them were used in the field ofelectrochemistry at present.In this dissertation, the research is devoted to enhancing the electrocatalyticactivity, stability and anti-poisoning of catalysts for DMFC electrocatalysts. Research was mainly about four kinds of biomass-based carbon materials were prepared fromnatural polymer materials, and they were applied to methanol oxidation reaction(MOR) and oxygen reduction reaction (ORR) on electrode in the catalytic reaction.The structural and chemical properties of biomass-based carbon materials werecharacterized by nitrogen adsorption (BET), X-ray powder diffraction (XRD) andtransmission electron microscopy (TEM), etc. The methods of cyclic voltammetry(CV), linear sweep method (LSV) and chronoamperometry (CA) were used to studythe catalytic performance of catalysts towards methanol oxidation reaction in acidicmedia and oxygen reduction reaction in alkaline media.The thesis is consists of three parts and the research details are as follows:Part I: The Carbonization of Cocoon and its Application as a ElectrocatalystSupport for Methanol OxidationCocoon-based carbon support (C-Cocoon) was prepared by directly carbonizingnatural polymer cocoon. After acid treatment, C-Cocoon was used to preparePt/C-Cocoon electrocatalyst, and the electrocatalyst was used for methanol oxidationreaction (MOR) in acidic media. The structural and chemical properties of sampleswere investigated using XRD, Raman, XPS, BET and SEM. The electrocatalyticactivity of catalyst towards methanol oxidation reaction (MOR) was studied by CVand CA electrochemical methods. Electrochemical tests showed that the currentdensity of Pt/C-Cocoon was up to19.55mA cm-2for MOR, has1.68times as manyas Pt/XC-72using the same preparation method, showed better methanol oxidationactivity, CO tolerance and stability.Part II: The Carbonization of Beef and its Application as a ElectrocatalystSupport for Methanol OxidationBeef-based carbon support (C-Beef) was prepared by directly carbonizingnatural polymer Beef. After acid treatment, C-Beef was used to preparePtRuIr/C-Beef (Metal loading of PtRuIr was10wt%; atom ratio of Pt: Ru: Ir was1:1:1) electrocatalyst, and the electrocatalyst was used for methanol oxidation reaction(MOR) in acidic media. The structural and chemical properties of sample wereinvestigated using BET, Raman, XRD, EDX and TEM. The electrocatalytic activity of catalyst towards methanol oxidation reaction (MOR) was studied by CV and CAelectrochemical methods. It was found that PtRuIr/C-Beef catalyst presented muchenhanced methanol oxidation activity, CO tolerance and stability towards methanoloxidation reaction (MOR) in comparison to PtRuIr/XC-72catalyst.Part III: The Modification of Biomass-based Carbon Materials and aComparative Study of them as Electrocatalysts for Oxygen Reduction ReactionFour kinds of biomass-based carbon materials (2C-Cocoon,2C-Beef,2C-Egg,2C-Blood) were prepared by secondarily carbonizing four kinds of natural polymermaterials, and they were directly used as cathode catalysts for oxygen reductionreaction (ORR) in alkaline media. The structural and chemical properties of fournon-metal catalysts were investigated using XRD, Raman and BET. Theelectrocatalytic activity of catalysts towards oxygen reduction reaction (ORR) wasstudied by CV, LSV and CA electrochemical methods. The experimental resultsshowed that non-metal catalysts have good catalytic activity, stability and methanoltolerance for oxygen reduction reaction (ORR) in0.1mol L-1KOH electrolyte.