Catalysts for direct ethanol fuel cells

Fuel cell technology is currently shifting very fast from fundamental research to real development. In addition to other aspects, this transition is possible because of the important improvements achieved in the field of electrocatalysis in the past decade. This perspective will give a focused overview summarizing the most outstanding contributions in the last 10 years in terms of activity and durability of the catalyst materials for ethanol oxidation and oxygen reduction reaction, respectively. In addition, it provides an outlook about new catalyst support materials with improved performance/stability, advanced characterization techniques, and fundamental studies of reaction mechanisms and degradation processes. All the studies referred to in this perspective significantly contribute to reaching the technical targets for PEFC commercialization.

Electrocatalysis for Polymer Electrolyte Fuel Cells: Recent Achievements and Future Challenges

Ethanol oxidation on Pt is a typical multistep and multiselectivity heterogeneous catalytic process. A comprehensive understanding of this fundamental reaction would greatly benefit design of catalysts for use in direct ethanol fuel cells and the degradation of biomass-derived oxygenates. In this work, the reaction network of ethanol oxidation on different Pt surfaces, including close-packed Pt{111}, stepped Pt{211}, and open Pt{100}, is explored thoroughly with an efficient reaction path searching method, which integrates our new transition-state searching technique with periodic density functional theory calculations. Our new technique enables the location of the transition state and saddle points for most surface reactions simply and efficiently by optimization of local minima. We show that the selectivity of ethanol oxidation on Pt depends markedly on the surface structure, which can be attributed to the structure-sensitivity of two key reaction steps: (i) the initial dehydrogenation of ethanol and (ii) the oxidation of acetyl (CH3CO). On open surface sites, ethanol prefers C-C bond cleavage via strongly adsorbed intermediates (CH2CO or CHCO), which leads to complete oxidation to CO2. However, only partial oxidizations to CH3CHO and CH3COOH occur on Pt{111}. Our mechanism points out that the open surface Pt{100} is the best facet to fully oxidize ethanol at low coverages, which sheds light on the origin of the remarkable catalytic performance of Pt tetrahexahedra nanocrystals found recently. The physical origin of the structure-selectivity is rationalized in terms of both thermodynamics and kinetics. Two fundamental quantities that dictate the selectivity of ethanol oxidation are identified: (i) the ability of surface metal atoms to bond with unsaturated C-containing fragments and (ii) the relative stability of hydroxyl at surface atop sites with respect to other sites.

Comprehensive mechanism and structure-sensitivity of ethanol oxidation on platinum: new transition-state searching method for resolving the complex reaction network.

Parallel pathways of ethanol oxidation: The effect of ethanol concentration

Ethanol electro-oxidation on carbon-supported Pt, PtRu and Pt3Sn catalysts: A quantitative DEMS study

The electrochemical oxidation of ethanol on platinum, rhodium, and platinum−rhodium electrodes is studied using on-line differential electrochemical mass spectrometry (DEMS) and in-situ infrared sp...

Electro-oxidation of ethanol on Pt, Rh, and PtRh electrodes. A study using dems and in-situ FTIR techniques

UNESP, Fac Agr & Vet, Dept Anim Morphol & Physiol, BR-14884900 Campus of Jaboticabal, SP, Brazil

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1439-0426.2008.01160.x

Histopathological changes in the gill, liver and kidney of pacu (Piaractus mesopotamicus, Holmberg, 1887) exposed to various concentrations of trichlorfon

In this work we have studied the direct detection and spectrometric capabilities for internal conversion electrons of an ion-implanted diode, developed in the framework of R&D programs at CERN, envisaging its use in an electron-gamma coincidence system for nuclear parameters measurements. The best energy resolution obtained until now, 12.6 keV (FWHM) for the 133Ba 320.32 keV electron emission, is sufficiently good to justify the use of this diode for spectrometry of low energy electrons.

http://www.sbfisica.org.br/bjp/files/v34_973.pdf

J. P. de Souza

Papers

Electro-oxidation of ethanol on Pt, Rh, and PtRh electrodes. A study using dems and in-situ FTIR techniques

Histopathological changes in the gill, liver and kidney of pacu (Piaractus mesopotamicus, Holmberg, 1887) exposed to various concentrations of trichlorfon

Manufactured silicon diode used as an internal conversion electrons detector