Experimental and model analysis of the co-oxidative behavior of syngas feed in an Intermediate Temperature Solid Oxide Fuel Cell

Abstract

-SOFCs). The activation of a co-oxidative route is a most distinguishing feature of Ce-based cells, compared to traditional SOFCs. SDC electrolyte supported ITSOFCs with Cu-Pd-CZ80 composite anodes and LSCF cathodes were tested under a wide range of operating conditions. Polarization and EIS measurements were collected at 600°C and 650°C with syngas mixtures (between 2.3 to 0.4 H2/CO ratio), H2/N2 mixtures (from 97 to 30% H2 v/v) and CO/CO2 mixtures (from 97 to 50% CO v/v). A 1D, dynamic and heterogeneous model of the cell was applied to analyze the polarization and the EIS curves. The kinetics of the reactions of H2 electrooxidation, CO electro-oxidation and O2 reduction were individually investigated and global power law rates were derived. The syngas experiments were simulated on a fully predictive basis and no parameter adjustment, confirming that the polarization behavior could be best reproduced exclusively by assuming the presence of the co-oxidative route. The IT-SOFCs were also exposed to biogas mixtures, revealing that the dry-reforming reaction was active. Milan, August 7 th 2015Dear Editor of the Journal of Power Sources, Please find attached our manuscript, entitled "Experimental and model analysis of the cooxidative behavior of syngas feed in an IT-SOFC" by Alessandro Donazzi, Morteza Rahmanipour, Matteo Maestri, Gianpiero Groppi, Luca Bardini, Alfonsina Pappacena and Marta Boaro, which we would like to submit for publication.In this paper, we present experimental and modeling results concerning the activation of a co-oxidative reaction mechanism in IT-SOFCs exposed to syngas mixtures. Novel, Ni-free, Ce-based IT-SOFCs are tested in a wide range of operative conditions, including biogas, syngas, H 2 /N 2 and CO/CO 2 mixtures. By means of model analysis, we show that the electro-oxidation of H 2 and the electro-oxidation of CO are active in parallel when syngas is fed to the cell, that is, the cell is able to directly oxidize CO in addition to H 2 . This is a most significant and promising result, associated to the presence of Ce in the anode formulation. For the first time in the case of ITSOFCs, the co-oxidative mechanism is numerically demonstrated. To accomplish this task, a onedimensional, dynamic and heterogeneous model is presented, which allows to predict both the polarization curves and the impedance spectroscopy curves. The model is based on fundamental conservation equations and also accounts for the presence of parasitic leakage currents, which characterize the behavior Ce electrolytes. A kinetic analysis is performed and power law rates are extracted for the electrocatalytic processes that are active in the cell.The work has not been previously submitted to the Journal of Power Sources, it has not been published previously in any form and is not under consideration for publication elsewhere. All the authors and the host authorities approve the manuscript.Thank you for your kind consideration. power law rates were derived. The syngas experiments were simulated on a fully predictive bas...

A Distributed Charge Transfer Model for IT-SOFCs Based on Ceria Electrolytes

“…Full details regarding the preparation procedure are found in a previous publication. 23 The main steps can be summarized as follows: a mixture of SDC powders and starch (30 wt%) were die-pressed with pure SDC powders, and the resulting bilayer was calcined in air at 1400…”

“…For both the reactions, the symmetry factors α, the activation energy and the species orders are taken from our previous work, 23 dedicated to IT-SOFCs with similar anode and cathode compositions. The values of the exchange current density are unknown parameters and are fitted to describe the polarization curves and the EIS spectra.…”

“…In the present work, a dynamic and distributed charge-transfer model is presented and validated for a button IT-SOFC with a MIEC electrolyte and composite electrodes fabricated in a previous study 23 with the aim of developing anodes that operate directly with biogas or biofuels. In order to consistently investigate the performance of the cell, the model takes into account the description of the leakage current based on physically-sound equations.…”

Experimental and Model Investigation of a Solid Oxide Fuel Cell Operated Under Low Fuel Flow Rate

“…The cell domain treats the problem of diffusion and reaction of gas species within the porous electrodes via the dusty gas model. This part of the model has been discussed in previous papers [32][33][34] and is not reported here for brevity. In the channel domain, mass, energy and momentum balances are included for the anodic and the cathodic gas streams.…”

Electrochemical Oxidation of Syngas on Nickel and Ceria Anodes

“…While major focus of these studies was the development of better performing anode, very little attention has been paid on understanding the electrochemistry of fuel oxidation on ceria. Available knowledge of possible reaction mechanism(s), rate-limiting processes and WGS catalytic activity of ceria at cell operating temperature is very limited [16,26,31,32,33,34] . Therefore, it is essential to investigate the reaction kinetics on nickel and ceria separately in order to realize the commercialization of nickel/ceria cermet anodes.…”