Analytical model is a valuable tool for the design process and performance optimization of fuel cell systems. In this paper, two-dimensional mathematical models of the tubular cathode in a direct ethanol fuel cell (DEFC), which include models of catalyst layer，support body, diffusion layer and gas flow, are developed to describe not only the electrochemical kinetics on the tubular cathode, but also multi-component transfer process in the tubular cathode. The model of spherical agglomerate is used in the catalyst layer, and the effect of ethanol penetration on oxygen reaction of the tubular cathode is also considered. Based on the model, Comsol Miphysics is used to simulate the concentration distribution of components and the current density distribution. Additional, the influence of diffusion layer and catalyst layer in the tubular cathode and the cell operating conditions on the performance of DEFC are analyzed. The results show that the mass transfer resistance exists in the diffusion layer, and the gas concentration decreases inside the battery. It is further showed that electrochemical reactions mainly happen in the catalyst layer, and oxygen concentration decrease rapidly at this time, while the water concentration can be increased.

High-temperature (700-900 °C) steam electrolysis based on solid oxide electrolysis cells (SOECs) is valuable as an efficient and clean path for large-scale hydrogen production with nearly zero carbon emissions, compared with the traditional paths of steam methane reforming or coal gasification. The operation parameters, in particular the feeding gas composition and pressure, significantly affect the performance of the electrolysis cell. In this study, a computational fluid dynamics model of an SOEC is built to predict the electrochemical performance of the cell with different sweep gases on the oxygen electrode. Sweep gases with different oxygen partial pressures between 1.01 × 10 3 and 1.0 × 10 5 Pa are fed to the oxygen electrode of the cell, and the influence of the oxygen partial pressure on the chemical equilibrium and kinetic reactions of the SOECs is analyzed. It is shown that the rate of increase of the reversible potential is inversely proportional to the oxygen partial pressure. Regarding the overpotentials caused by the ohmic, activation, and concentration polarization, the results vary with the reversible potential. The Ohmic overpotential is constant under different operating conditions. The activation and concentration overpotentials at the hydrogen electrode are also steady over the entire oxygen partial pressure range. The oxygen partial pressure has the largest effect on the activation and concentration overpotentials on the oxygen electrode side, both of which decrease sharply with increasing oxygen partial pressure. Owing to the combined effects of the reversible potential and polarization overpotentials, the total electrolysis voltage is nonlinear. At low current density, the electrolysis cell shows better performance at low oxygen partial pressure, whereas the performance improves with increasing oxygen partial pressure at high current density. Thus, at low current density, the best sweep gas should be an oxygen-deficient gas such as nitrogen, CO2, or steam. Steam is the most promising because it is easy to separate the steam from the by-product oxygen in the tail gas, provided that the oxygen electrode is humidity-tolerant. However, at high current density, it is best to use pure oxygen as the sweep gas to reduce the electric energy consumption in the steam electrolysis process. The effects of the oxygen partial pressure on the power density and coefficient of performance of the SOEC are also discussed. At low current density, the electrical power demand is constant, and the efficiency decreases with growing oxygen partial pressure, whereas at high current density, the electrical power demand drops, and the efficiency increases.

By using the mesocarbon microbead (MCMB) and graphite as raw material, the tubular cathode green bodies of a direct ethanol fuel cell（DEFC）are shaped by the gelcasting technology and the tubular cathode is prepared by spraying the diffusion layer and the Pt/C catalyst layer after the sintering process. Through the tubular cathode physical performance and electrical property test, the advantages and disadvantages of cathode tube performance are studied at different graphite proportion. The results showed that with the increase of graphite, the ratio porosity of cathode tube support body increases at first and then decreases. However, the density has a converse trend. While the maximum porosity of the cathode tube is more than 0.5 and the corresponding density is 0.95g/cm3. Strength test showed that the cathode tube strength is better with the graphite ratio from 0 to 40 percent and can meet the actual needs. Electrical property tests showed that the cathode tube has higher current density with the graphite ratio of 40 and 50 percent.