RODRIGO PIRES DA SILVA
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Artigo IPEN-doc 30769 Optimized interfaces for PBI-based high-temperature direct ethanol fuel cells2024 - SILVA, RODRIGO P. da; MATOS, BRUNO R. de; FONSECA, FABIO C.; SANTIAGO, ELISABETE I.The present study combines innovative strategies aiming at enhanced performance of direct ethanol fuel cells (DEFC) by modifying interfaces at both electrodes and electrolyte. Increasing the operating temperature to 180 °C to promote faster kinetics and thermally activated processes taking place in DEFC was possible by using phosphoric-acid-doped PBI (polybenzimidazole) composite electrolytes. The properties of the PBI electrolytes were improved by adding SiO2 as an inorganic second phase, promoting an increase in the proton conductivity and inhibiting ethanol crossover. Optimizing electrode reactions by increasing the triple-phase boundary was demonstrated by using a powdered-based PBI “ionomeric” concept to boost the performance of the proton exchange membrane fuel cell. The electrochemical characterization of the high-temperature direct ethanol fuel cells (HT-DEFC) showed that combining the strategies for the optimized electrode and electrolyte was crucial for increasing the performance of membrane electrode assemblies operating at 180 °C.Artigo IPEN-doc 29609 Numerical validation of direct ethanol fuel cell operating at high temperature2023 - PANESI, A.R.Q.; SILVA, R.P.; SANTIAGO, E.I.In the present work, a three-dimensional steady-state model was developed to analyze the performance of high-temperature direct ethanol fuel cell (HT-DEFC) based on polybenzimidazole (PBI) electrolytes. A non-isothermal model of a HT-DEFC setup using a PBI/H3PO4 membrane was employed using computational fluid dynamics (CFD). This work is aiming at a validation of experimental data of HT-DEFC prototypes based on the simulation of polarization curves. The model predicts the mole concentration of H3PO4, heat and current density distributions, as well as mass fraction ethanol during operation at 180 °C. The heat transfer model was coupled to the electrochemical and mass transport, allowing that a particular heating configuration was investigated considering the temperature distribution on the PBI membrane. We have found that temperature and relative humidity (RH) are mostly related to PBI properties resulting from H3PO4 lixiviation and conductivity decreasing as well as ethanol crossover strongly interferes on the oxygen reduction reaction (ORR) rate, leading to poor HT-DEFC performance.