Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

Abstract

In this study, 2 models are developed to investigate the performance of a solid oxide electrolysis cell (SOEC) for CO 2 electrolysis at different levels. The first model is a one-dimensional model which is basing on a previously developed electrochemical model for steam electrolysis and considered all overpotentials in the SOEC. The second model is a two-dimensional thermal-fluid model consisting of the 1D model and a computational fluid dynamics (CFD) model. It is found that the mean electrolyte temperature initially decreases with increasing operating potential, reaches the minimum at about 1.1V and increases considerably with a further increase in potential. At the thermal-neutral voltage (1.463V at 1173K), the calculated mean electrolyte temperature matches the inlet gas temperature. Increasing the operating potential increases both the local current density and the electrolyte Nernst potential. The electrochemical performance can be improved by increasing the inlet gas velocity from 0.2ms -1 to 1.0ms -1 but further increasing the inlet gas velocity will not considerably enhance the SOEC performance. It is also found that a change of electrode permeability in the order of 10 -16 -10 -13 m 2 does not noticeably influence the SOEC performance in the present study, due to negligible convection effect in the porous electrodes.

2D thermal modeling of a solid oxide electrolyzer cell (SOEC) for syngas production by H2O/CO2 co-electrolysis

“…In order to clarify the above issues, a 2D thermal model is developed to analyze the coupled heat/mass transfer and chemical/electrochemical reactions in an SOEC for H 2 O/CO 2 co-electrolysis. It is based on and extended from the previous models for H 2 O electrolysis [6,18] and CO 2 electrolysis [33] as well as a recent electrochemical model for co-electrolysis [34]. The modeling results show that CH 4 formation via reversed steam reforming (Eq.…”

“…The reaction rate of WGSR is positive near the inlet and negative in most of the porous cathode in the downstream. The positive rate of WGSR is caused by relatively high concentration of CO at the cathode-electrolyte interface near the inlet, since CO is more difficult to diffuse to the cathode channel than H 2 due to higher diffusion coefficient of H 2 than CO [18,33,48]. In the downstream, the reversed WGSR is favored due to considerably increased H 2 concentration by H 2 O electrolysis.…”

“…The effect of WGSR is small due to a small average WGSR rate of the cell. As the operating potential (1.5 V) is higher than the thermal neutral voltages (TNV) for electrolysis of H 2 O and CO 2 [18,33], the heat generation from overpotential losses exceeds heat demand for electrolysis reaction. Fig.…”

Accurate predictions of H2O and CO2 co-electrolysis outlet compositions in operation

“…Along with high experimental interest and technical developments, many modeling studies have been devoted to H 2 O electrolysis [17e23], CO 2 electrolysis [24] and/or coelectrolysis [16,25e28] of steam and carbon dioxide. Modeling can be a powerful approach to get better insight on the complex mechanisms occurring inside a SOC, and to optimize the electrolysis processes.…”

Modeling CO2 electrolysis in solid oxide electrolysis cell

“…They in fact have operated an SOFC in the electrolysis mode by applying potentials higher than open circuit potential. Ni has modeled these experiments using a 2D numerical model of the flow channels [5]. Although, the flow channels are modeled in 2D, the concentration loss due to porous media transport is calculated using analytical expression.…”