Study On Controllable Preparation Of Pt And Pd Based Catalysts And Their Performance For Electrooxidation Of Small Organic Molecules

Fuel cell is a new type of energy conversion device,which has the characteristics of high energy conversion efficiency,safety,portability and pollution-free,so it has been gain much attention from researchers.The research of high efficient catalyst for electrooxidation of small organic molecules strongly affects the wide application and development of commercial fuel cell.The main catalysts materials for small organic molecules electrooxidation reaction are precious metal,such as Pt and Pd based catalysts.However,the such electrocatalysts have disadvantages,such as the higher cost of precious metal,low catalytic performance,easy poisoning and easy aggregation.The above problems could be effectively solved via adjusting the composition,morphology and structure of Pt and Pd nanomaterials as well as modifying the support materials.This work mainly focuses on achieving the purpose of regulating the electrooxidation performance of small organic molecules by synergistic effect,electronic effect,enhanced electrochemical active area and stable structure among the components of the catalyst,which resulted from regulating the composition,morphology,structure and support of the catalyst.The main research work is as follows:Linear cross-linked Pt Cu network(Pt Cu-LCN)catalyst was successfully synthesized through a simple ethylenediaminetetraacetic acid disodium salt(EDTA-2Na)assisted one step co-reduction method.The formation of special structure is due to the chelation of ethylenediaminetetraacetic acid disodium salt instead of the adsorption of the surfactant,which easy adsorb on the surface active sites of Pt.The linear cross-linked network structure with abundant lattice corners and lattice steps exposes more specific surface area and provide more efficient active sites to absorbed methanol.Meanwhile,the addition of the second metal Cu could promote the removal of Pt surface CO-like intermediates via adjusting the electronic structure of Pt.Therefore,the Pt Cu-LCN exhibits excellent activity and stability for methanol oxidation reaction(MOR)in an acidic medium.The MOR mass activity of Pt Cu-LCN is 891.69m A·mg_Pt^-1,which is almost 4.43 times higher than that of commercial Pt black-JM.After 7200s,the activity of Pt Cu-LCN with a residual value of 42.8%is compared to the initial current density,which is higher than that of commercial Pt black-JM.A ternary TePbPt alloy nanotube(NT)catalyst was designed based on the following rational considerations.Pb and Te,which could facilitate the removal of adsorbed CO-like intermediates via bifunctional mechanisms and adjust the electronic structure of Pt,respectively,were introduced into the alloy NT catalyst.The as-designed alloy NT catalyst with a uniform,ultrathin,and ultralong structure was precisely prepared through the hard template method with pre-synthesized Te Pb nanowires used as the sacrificial template.The NT catalyst exhibits excellent performances towards methanol oxidation reaction(MOR)both in activity and durability in an acidic medium.Further characterizations reveal that the enhanced performances are attributed to the adjusted electronic and chemical structures of Pt via the interactions among Pt,Te,and Pb according to complex mechanisms,which are illustrated in detail.The MOR activity of ternary TePbPt alloy nanotube is 891.69 m A·mg_Pt^-1,which is almost 2.7 times higher than that of commercial Pt black-JM.After 1000 cycles ADT tests,TePbPt NT catalyst exhibits only 14.9%decrease(residual 85.1%)of the initial forward peak current density towards MOR,which is obviously better than commercial Pt black catalyst.Phosphorus doped graphene supported Pt Ni P nanocluster catalyst(Pt Ni P/P-graphene)was successfully prepared via a simple hypophosphite-assisted co-reduction method.The improved anchoring force and increased anchoring sites of graphene support result from phosphorus doping as well as size-confined growth effect of Na H₂PO₂ leads to uniform dispersion of ultrafine Pt Ni P nanoclusters.Doped P also promotes the removal of CO-like intermediate by adjusting Pt electronic structure combining with alloyed Ni via electronic effects.As a result,the as-prepared Pt Ni P/P-graphene catalyst with more exposed active sites and optimized electronic structure of Pt alloy shows excellent electrocatalytic performances for methanol oxidation reaction(MOR)both in activity and durability in an acidic medium.The MOR performance of Pt Ni P/P-graphene is 826.1 A·g_Pt^-1,which is almost 2.58 times higher than that of commercial Pt black-JM.After 1000 cycles ADT tests,Pt Ni P/P-graphene catalyst exhibits only 36.0%decrease(residual 64.0%)of the initial forward peak current density towards MOR,which is obviously better than commercial Pt/C-JM catalyst.Uniform sea urchin-like Au@Pd formic acid oxidation reaction(FAOR)catalysts with dendritic core-shell structure were successfully prepared via nanocatalysts self-assembly process.High electrochemical surface area with more exposed active sites as well as the suitable lattice strain were confirmed as influencing factor to enhance intrinsic activity and facilitate kinetic reaction rate,resulting improved FAOR performance.Specifically,as tuning the status of surface dendritic Pd,lattice strain presented different influence on the catalytic performance.Stronger lattice strain would facilitate the surface adsorption of dissociate formic acid on the surface Pd.While,weaker lattice strain would make surface desorption of the intermediate species on surface Pd easily resulting regeneration of active sites.In this work,the optimized Au₇₁@Pd₂₉ DCS exhibits enhanced activity with the current density of 1405 A·g_Pd^-1,which is8.8 times higher than that of the commercial Pd black(160 A·g_Pd^-1),as well as obvious enhanced durability.