The Construction Of The Layered Double Hydroxide Supported Pt Catalytic System And The Study On The Catalytic Oxidation Of Methanol

Direct methanol fuel cell(DMFC)has became a research hotspot in the field of energy transportation and storage in recent years due to its unique advantages,such as high energy density,environmental friendliness,simple operation and portability.Although DMFC is considered as one of the most promising devices for portable power applications,there still exist some problems,the most prominent of which is the slow electrochemical kinetics of the anode.At present,the most commonly used DMFC anode catalyst is Pt-based catalyst,which shows a high catalytic performance for the oxidation of methanol.It is important to prepare ultrafine size Pt and Pt-M alloy nanoparticles(NCs)to improve the catalytic activity and minimize the consumption of Pt.Compareing with the larger particle size catalyst,the ultrafine NCs will greatly increase the catalytic activity,due to its specific surface area and high proportion of the corner atoms.According to the main problems existing in DMFC,the composite substrate of Pt-based catalyst was synthesized based on layered bimetallic hydroxide to enhance the catalytic performance and the stability of catalyst.The research work carried out mainly includes the following three aspects:1.Electrodeposition load of Pt nanoparticles on Nife-LDH/RGO to form intercalation structure for efficient electrocatalytic methanol electro-oxidationThe nickel-iron layered double hydroxide/reductive oxidized graphene(Ni Fe-LDH/RGO)composite was prepared by a pot of hydrothermal synthesis method and a precursor salt solution of Ni Fe-LDH was added as part of the process of graphene oxidation and reduction.The Pt was loaded on the Ni Fe-LDH/RGO surface as a precious metal catalyst,the precious metal composite catalyst Pt/ nickel-iron layered double hydroxide/reducing oxidized graphene(Pt/Ni Fe-LDH/RGO)by electrodeposition method.As an effective intercalation material,Ni Fe-LDH effectively suppresses the stacking of RGO,thus providing a greater specific surface area for the load of Pt nanoparticles.2.In-situ loading of Pt nanoparticles on vertical growth Ni Co-LDH for catalytic methanol oxidationFirst,the foamed nickel was treated with HCl to make the surface defect,and then added into the reactor along with the Ni Co-LDH precursor salt solution.The Ni Co-LDH nanoparticles will grow vertically on the surface of foamed nickel based on hydrothermal reaction,and thereby get the Ni Co-LDH/Ni foam composite catalyst substrate.Because of the special vertical growth morphology of nano-flake,the stacking phenomenon in the reaction process of hydrotalcite can be effectively prevented,providing the specific surface area for the load of nanometer catalyst particles.Pt NPs anchored on Ni Co-LDH/NF with uniform dispersion and narrow size distribution form the Pt/Ni Co-LDH/NF catalyst by in situ reduction,due to the redox reaction between Co2+(Co(OH)2)in Ni Co-LDH/NF and Pt Cl62-,in which the Ni Co-LDH serves as both a morphology-controlling support and a reductant without any external agent.3.In-situ loading of Pt Pd alloy on vertical growth Ni Co-LDH for catalytic methanol oxidation.In order to further enhance the catalytic activity of catalyst,it is feasible to use hydrothermal reaction on the surface of carbon fiber vertical growth Ni Co-LDH nanoplates.After soaking the Ni Co-LDH in a certain concentration of Na2 Pt Cl6 and K2 Pd Cl4 for a while,the Pt Pd nanoparticles,which has small diameter and uniform distributed,in situ grown on the surface of Ni Co-LDH nanoplates can be obtained due to the redox reaction between Pt Cl62-,Pd Cl42-with Co(OH)2.Because of the special vertical growth morphology of nano-flake,the stacking phenomenon in the reaction process of hydrotalcite can be effectively prevented,providing the specific surface area for the load of nanometer catalyst particles.It is shown that compared with the separate Pt,the D-band vacancy in the alloy makes the Pt-Pt more favorable for the separation of the atomsby introducing a cheaper transition metal Pd.Due to the atomic dilution of Pt in the alloy,the second metal can inhibit or reduce the adsorption of methanol on Pt,thus greatly improving the stability of the catalyst.