ANDRE D. TAYLOR
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Artigo IPEN-doc 20035 Catalyst and electrolyte synergy in Li-Osub(2) batteries2014 - GITTLESON, FORREST S.; SEKOL, RYAN C.; DOUBEK, GUSTAVO; LINARDI, MARCELO; TAYLOR, ANDRE D.Understanding the interactions between catalyst and electrolyte in Li–O2 systems is crucial to improving capacities, efficiencies, and cycle life. In this study, supported noble metal catalysts Pt/C, Pd/C, and Au/C were paired with popular Li–O2 electrolyte solvents dimethoxyethane (DME), tetraglyme (TEGDME), and dimethyl sulfoxide (DMSO). The effects of these combinations on stability, kinetics, and activity were assessed. We show evidence of a synergistic effect between Pt and Pd catalysts and a DMSO-based electrolyte which enhances the kinetics of oxygen reduction and evolution reactions. DME and TEGDME are more prone to decomposition and less kinetically favorable for oxygen reduction and evolution than DMSO. While the order of oxygen reduction onset potentials with each catalyst was found to be consistent across electrolyte (Pd > Pt > Au), larger overpotentials with DME and TEGDME, and negative shifts in onset after only five cycles favor the stability of a DMSO electrolyte. Full cell cycling experiments confirm that catalyst–DMSO combinations produce up to 9 times higher discharge capacities than the same with TEGDME after 20 cycles (B707.4 vs. 78.8 mA h g1 with Pd/C). Ex situ EDS and in situ EIS analyses of resistive species in the cathode suggest that improvements in capacity with DMSO are due to a combination of greater electrolyte conductivity and catalyst synergies. Our findings demonstrate that co-selection of catalyst and electrolyte is necessary to exploit chemical synergies and improve the performance of Li–O2 cells.Artigo IPEN-doc 19038 Development and electrochemical studies of membrane electrode assemblies for polymer electrode alkaline fuel cells using FAA membrane and ionomer2013 - CARMO, MARCELO; DOUBEK, GUSTAVO; SEKOL, RYAN C.; LINARDI, MARCELO; TAYLOR, ANDRE D.This paper provides guidelines on the fabrication and operation of alkaline fuel cells using quaternary ammonium hydroxide anion exchange membrane (FAA-3 e fumatech), and includes a discussion of the electrode kinetic parameters based on the composition of the catalytic layer. The best peak power density performance, 223 mW cm 2 was obtained with an electrode formed from Pt/C, 0.8 mgPt cm 2 and 25% of FAA-3 ionomer in the catalyst layer for both the cathode and the anode. We demonstrate that the platinum loading can be lowered to values close to 0.5 mgPt cm 2 , without appreciably affecting the fuel cell performance characteristics. The experimental fuel cell data were analyzed using theoretical models of the electrode structure and its kinetics studied over the assembling parameters. We show that most of the electrode systems present limiting currents, with some showing diffusion limitations in the gas channels and/or in the ionomer film covering the catalyst nanoparticles. We also provide some general strategies using Tafel slopes on evaluating the ionomer interaction with the electrode kinetics for the oxygen reduction reaction.Artigo IPEN-doc 17240 Enhanced activity observed for sulfuric acid and chlorosulfuric acid functionalized carbon black as PtRu and PtSn electrocatalyst support for DMFC and DEFC applications2011 - CARMO, MARCELO; BRANDALISE, MICHELE; OLIVEIRA NETO, ALMIR; SPINACE, ESTEVAM V.; TAYLOR, ANDRE D.; LINARDI, MARCELO; POCO, JOÃO G.R.