Studies On The Formation Of Catalyst Layers With Ordered Structure Using Layer-by-layer Deposition For Direct Methanol Fuel Cells

Direct methanol fuel cell (DMFC) has the advantages of high energy conversion rate, high energy density, easy to use and carry, nearly zero emissions, it has a great application prospect in national defense, communication areas and portable electric. The heart component of DMFC systems is catalyst layers (CLs), which is vital to the performance of the fuel cells. In this work, anode and cathode CLs with different structures, CLs with structure and material gradient variation have been fabricated via change the deposition distance and the competent of CLs suspension using electrohydrodynamic atomization (EHDA). The CLs were assembled to fuel cell to test the performance of the fuel cell, in addition, the CLs structure affect the performance of fuel cell was also analyzed.Schematic representations of the growth of deposited CLs using Pt/C suspension were analyzed. The thickness of the CLs increased with deposition time and working distance. The porosity of the CLs and the dispersity of the catalysts increased when the working distance increased, at high working distance, catalyst agglomerations were reduced. The relationship between the porosity of the CLs and the atomization parameters were studied. The cathode and anode CLs were deposited on different substrate (carbon paper and proton exchange membrane (PEM)), respectively. When assemble the deposited CLs into membrane electrode assembly (ME A) and fuel cell to test the performance of the CLs, the result showed that the performance of CLs fabricated on PEM is better than the CLs fabricated on carbon paper.The relationship between the CLs structure and the performance of the fuel cell was simulated using two-phase model. Thin film and large specific surface area of the CLs can obtain the low anode polarization curve and high performance of the cell. Cathode and anode CLs with different structures were prepared, the catalysts in CLs presented well-packed, the porosity and specific surface area of CLs increased with working distance. Then assemble the CLs into fuel cells to test the performance, the results show that large specific surface area of the CLs can obtain the small anode polarization curve and high performance of the cell, which is same with the simulation’s. CLs prepared by using EHDA desiposition method were assembled to fuel cell, the peak power density of74mW·cm-2at80℃.CLs with structure and material gradient variation were prepared. The Pt-Ru and Pt loadings of anode and cathode CLs were1.2mg·cm-2and0.4mg·cm-2, respectively. The structure of the CLs changes from porous to dense, the mass of the Nafion is also increase from the gas diffusion layer to the PEM. Then, assemble the CLs into air-breathing and active fuel cells to test the performance. The cell performance increased when the temperature and oxygen flux rose, but when the methanol flux increased, the performance of the cell is decreased. The performance of the CLs with structure and material gradient variation is double that of the CLs with no material and structure gradient variation at30℃.