A three-dimensional non-isothermal model for a membraneless direct methanol redox fuel cell

In the membraneless direct methanol redox fuel cell (DMRFC), three-dimensional electrodes contribute to the reduction of methanol crossover and the open separator design lowers the system cost and extends its service life. In order to better understand the mechanisms of this configuration and further optimize its performance, the development of a three-dimensional numerical model is reported in this work. The governing equations of the multi-physics field are solved based on computational fluid dynamics methodology, and the influence of the CO2 gas is taken into consideration through the effective diffusivities. The numerical results are in good agreement with experimental data, and the deviation observed for cases of large current density may be related to the single-phase assumption made. The three-dimensional electrode is found to be effective in controlling methanol crossover in its multi-layer structure, while it also increases the flow resistance for the discharging products. It is found that the current density distribution is affected by both the electronic conductivity and the concentration of reactants, and the temperature rise can be primarily attributed to the current density distribution. The sensitivity and reliability of the model are analyzed through the investigation of the effects of cell parameters, including porosity values of gas diffusion layers and catalyst layers, methanol concentration and CO2 volume fraction, on the polarization characteristics

Effects of composition on electrochemical properties of a non-precious metal catalyst towards oxygen reduction reaction

A family of non-precious metal catalysts, Co-PPy-TsOH/C, has been synthesized with different amount of pyrrole and p-toluenesulfonic acid (TsOH). Elemental contents of Co, N, C, S, H and O in the obtained catalysts have been measured with physicochemical techniques and the performance of these catalysts towards oxygen reduction reaction (ORR) have been evaluated with electrochemical techniques. Then, the results obtained have been discussed with principal component analysis and linear correlation analysis to find the correlation/anticorrelation between the composition and electrochemical properties. It is revealed that the used amount of pyrrole has much more apparent effect than TsOH on elemental contents in the Co-PPy-TsOH/C catalysts, while both of them influence the ORR activity and mechanism of the catalysts. Besides, the effects of the contents of each element on the electrochemical performance have also been analyzed to guide the future development of similar catalysts. ? 2013 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved