Numerical simulation of solid oxide fuel cells comparing different electrochemical kinetics

Abstract

Solid oxide fuel cells (SOFCs) produce electricity with high electrical efficiency and fuel flexibility without pollution, for example, CO 2 , NO x , SO x, and particles.Still, numerous issues hindered the large-scale commercialization of fuel cell at a large scale, such as fuel storage, mechanical failure, catalytic degradation, electrode poisoning from fuel and air, for example, lifetime in relation to cost. Computational fluid dynamics (CFD) couples various physical fields, which is vital to reduce the redundant workload required for SOFC development. Modeling of SOFCs includes the coupling of charge transfer, electrochemical reactions, fluid flow, energy transport, and species transport. The Butler-Volmer equation is frequently used to describe the coupling of electrochemical reactions with current density. The most frequently used is the activation-and diffusion-controlled Butler-Volmer equation. Three different electrode reaction models are examined in the study, which is named case 1, case 2, and case 3, respectively. Case 1 is activation controlled while cases 2 and 3 are diffusion-controlled which take the concentration of redox species into account. It is shown that case 1 gives the highest reaction rate, followed by case 2 and case 3. Case 3 gives the lowest reaction rate and thus has a much lower current density and temperature. The change of activation overpotential does not follow the change of current density and temperature at the interface of the anode and electrolyte and interface of cathode and electrolyte, which demonstrates the non-linearity of the model. This study provides a reference to build electrochemical models of SOFCs and gives a deep understanding of the involved electrochemistry.

Multi-doped ceria-based composite as a promising low-temperature electrolyte with enhanced ionic conductivity for steam electrolysis

“…The activation energy is the energy which is essential to begin the reaction and thus determines the overall reaction state. 88 The maximum electrical conductivity obtained for the 5LB1C-1 sample was 2.96 × 10 −2 at 750 °C with an activation energy of 0.13 eV. The activation energy of pure GDC sintered at 950 °C was 0.83 eV.…”

Optimal Heat‐Up Planning of a Solid Oxide Fuel Cell with and without Hot Air Recycling by Considering Energy, Time, and Temperature Gradient

“…Figure 1 shows the schematic view of a single planar SOFC, consisting of a positive electrode (cathode), an electrolyte, a negative electrode (anode) (so-called PEN structure), and one interconnect on each side. [44,45] The electrodes are made of porous materials to facilitate the transportation of gaseous reactants. The solid electrolyte is an ion-conducting material that prevents the electrons to pass through.…”

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

“…13 When these pre-applicative cells are tested individually, single channel models are applied, which include the interconnectors and describe a single repeating unit (SRU). [14][15][16][17][18][19][20][21] Multi-dimensional models or finite element methods are utilized to capture the channel fluid dynamics, the patterns of the gas distribution under the interconnector ribs, or the diffusive transport in electrodes with graded porosity. Energy balances are introduced for the SRU, which frequently rely on the assumption of adiabatic channels, and on the attainment of local temperature equilibrium between the solid phase and the gas phase in the electrodes.…”