Otimização de anodos eletrocatalíticos para reforma interna de etanol em pilhas a combustível de óxido sólido

Abstract

In this work, solid oxide fuel cells (SOFCs) with different supports (NiO/YSZ anode and YSZ electrolyte) were fabricated and evaluated using NiO and YSZ powders, and CGO/Co and LSCF pastes to optimize the electrolyte and electrode films. Aiming at the internal reforming of ethanol at the anode, a tungsten oxide (WO3) catalyst was tested in circular planar cells (50 mm in diameter, ~0.23 mm in thickness) consisting of a cathode layer, two electrolyte layers, and three anode layers (support, functional, and catalytic). The physicochemical characterization of the materials was performed by X-ray diffraction and scanning electron microscopy, and the electrochemical performance was evaluated by electrochemical impedance spectroscopy and linear voltammetry at 740 °C. The complete cell with anode support and WO3 catalyst showed superior performance in the direct reforming of ethanol (33% v/v in water), demonstrating low polarization resistance (1.05 ohm.cm⁻²), current density of 0.66 A.cm⁻² and maximum power density of 258 mW.cm⁻². In comparison, the cell with anode support without catalyst, using hydrogen, exhibited polarization resistance of 1.389 ohm.cm⁻², current density of 0.287 A.cm⁻² and maximum power density of 135 mW.cm⁻². The electrolyte-supported cell, using ethanol as fuel and WO3 catalyst, showed a polarization resistance of 17.97 ohm.cm⁻², a current density of 0.29 A.cm⁻² and a maximum power density of 127 mW.cm⁻² at 740 °C. In contrast, the electrolyte-supported cell without catalyst, operating with hydrogen, demonstrated a polarization resistance of 7.22 ohm.cm⁻², a current density of 0.122 A.cm⁻² and a maximum power density of 58 mW.cm⁻². The results indicate good electrochemical performance and a promising catalytic activity of WO3 for direct reforming of ethanol. The performance can be improved by optimizing the film thickness and the tungsten concentration in the anode.