1,721,440 research outputs found
"Core -Shell" ORR Nano-Electrocatalysts Based on a PtNi Carbon Nitride “Shell” and Conducting NP “Core”
No full textTecniche di assorbimento e di emissione atomica per l'analisi di elementi in traccia nei sistemi biologici
No full textPlurimetallic Nano-electrocatalysts based on Carbon Nitride Supports for the ORR Processes in PEM Fuel Cells
No full textDevelopment of Plurimetallic Nano-electrocatalysts based on Carbon Nitride Supports for the ORR Processes in PEM Fuel Cells
No full textBroadband electric spectroscopy: a powerful tool for the determination of charge transfer mechanisms in ion conductors
No full textIonically conducting materials (ICMs) are of great importance for the fabrication of portable batteries for electronic devices such as computers, tools, video and still cameras, and for the development of fuel cell and battery-powered electric vehicles, dye-sensitized solar cells, supercapacitors, and sensors. It has been suggested that conductivity in ICMs occurs via a number of different processes. The predominant conductivity processes are attributed to: (a) the migration of ions between coordination sites in the host materials, and (b) the increase of conductivity due to relaxation phenomena involving the dynamics of the host materials. Ions hopping to new chemical environments can lead to successful charge migration only if ion-occupying domains relax via reorganizational processes, which in general are coupled with relaxation events associated with the host matrix. In this work, the instruments used in the comprehensive study of the electric response of ICMs are described, and the basic tools to understand broadband electric spectroscopy are provided. The first part of the presentation reviews the general phenomena and the basic theory underlying each type of electric response that materials may exhibit when they are subjected to static or dynamic electric fields. Afterwards, the strategies of data analysis, which is accomplished using specific empirical or theoretical models, are described in detail. The final part of the presentation discusses the methodologies for accurate data collection
Charge transfer mechanisms in ion conducting materials by broadband electrical spectroscopy (BES)
No full textA comprehensive understanding of the charge transfer mechanisms of ion conducting materials (ICMs) is of crucial importance both for fundamental research and for a host of practical applications, including primary and secondary batteries, fuel cells, dye-sensitized solar cells, supercapacitors and sensors. A wide variety of ICMs has been proposed, based on: (a) different families of polymer electrolytes; (b) ionic liquids (ILs); and (c) classical ion-conducting ceramics. In these materials, the long-range charge transfer events take place owing to complex processes, which involve several possible relaxation phenomena, such as: (a) ion hopping events between ion coordination sites; (b) relaxation modes of the host matrix; and (c) polarization effects occurring at the interfaces between the different domains characterizing the materials. Broadband electrical spectroscopy (BES) is a powerful tool for the accurate investigation of the roles played by electrical relaxation events in the charge transfer processes. Indeed, BES allows to carefully detect the fundamental relaxations governing the long-range charge transfer mechanisms and to correlate them to the morphology of ion-conducting materials. This presentation overviews results of the application of BES in the study of the charge transfer mechanisms of a variety of ICMs, including: (a) polymer electrolytes based on alkaline and alkaline-earth ions; (b) pristine and hybrid inorganic-organic proton-conducting and anion-conducting membranes; and (c) protic and aprotic ILs. The general phenomena and the fundamental theory underlying the interpretation of the events characterizing the electric response of the materials is also described. Finally, the models adopted for the interpretation of conductivity mechanisms are described and a unified conductivity mechanism is proposed
Structure, properties and proton conductivity of Nafion/[(TiO2)·(WO3)0.148]yTiO2 nanocomposite membranes
No full textAdvanced High-performing Nanostructured Materials for Proton Electrolyte Membrane Fuel Cells
No full textCharge transfer mechanisms in Anionic Membranes by Broadband Electric Spectroscopy
No full textAnionically conducting materials (ACMs) are of great importance for the fabrication of alkaline fuel cells. It has been suggested that conductivity in ACMs occurs via a number of different processes. The predominant conductivity processes are attributed to: (a) the migration of anions between coordination sites in the host materials, and (b) the increase of conductivity due to relaxation phenomena involving the dynamics of the host materials. Hopping of anions to new chemical environments can lead to successful charge migration only if anion-occupying domains relax via reorganizational processes, which in general are coupled with relaxation events associated with the host matrix. In this presentation, the instruments used in the comprehensive study of the electric response of ACMs are described, and the basic tools to understand broadband electric spectroscopy are provided. The first part of the presentation reviews the general phenomena and the basic theory underlying each type of electric response that materials may exhibit when they are subjected to static or dynamic electric fields. Afterwards, the strategies of data analysis, which is accomplished using specific empirical or theoretical models, are described in detail. The final part of the presentation discusses the methodologies for accurate data collection
A novel polymer electrolyte based on oligo(ethylene glycol) 600, K2PdCl4, and K3Fe(CN)6
No full textNew electrolytic systems were prepared by reacting K3Fe(CN)6 and K2PdCl4 in a mixture of water and poly(ethylene glycol) 600 (PEG). The reaction occurs in two steps: first a gel is formed, which then shrinks, releasing the solvent. The product thus obtained has the consistency of a smooth, solid plastic paste and is very stable. The influence of the reaction mixture on the structure, morphology, and conductivity of the products was investigated carrying out three preparations (I, II, III) at increasing ratio PEG 600/H2O. By FT-IR studies and analytical data it was concluded that these materials are inorganic-organic networks containing CN bridges between Fe and Pd atoms and PEG 600 bridges between Pd atoms. Scanning electron microscopy studies revealed that the morphology of polymers I, II, and III is significantly influenced by the conditions of the synthesis. Conductivity measurements made at different temperatures showed that polymers I, II, and III conduct ionically. The conductivity of polymer I, which was synthesized with the highest water/PEG 600 ratio, is on the order of 1.4x10-3 S/cm at 25°C
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