Investigation On Improvement For Graphite Felt Cathode For Direct Liquid Redox Methanol Fuel Cell

Graphite felt(GF) is commonly used as electrode materials in direct liquid redox methanol fuel cell due to its stability as anode and cathode, good fluid permeability, high surface area and availability at a reasonable cost. However, its poor hydrophilicity and low electrochemical activity, limits its use as active electrode material. Consequently, a great deal of attention has been directed towards the introduction of nitrogen and boron impurity atoms to change the electronic structure of carbon atoms in GF, and then improve its electrochemical performance. Although there have been sporadic reports relate to nitrogen doped GF, the research of nitrogen doped GF used in direct liquid redox methanol fuel cell as cathode is still in the blank. The research of boron doped GF is also not reported.A direct liquid redox methanol fuel cell was fabricated. The performance of the cell was explored from the operating temperature of the cell and the thickness of GF relative to the cathode groove. The results showed that increased temperature may improve the proton conductivity of Nafion membrane and catalyst activity, thus improved the battery performance. Compared with the depth of cathode groove, the thick GF has better electric contact with the anode half membrane electrode assembly, which is more conducive to the charge transfer and inhibit the formation of CO2 gas bubbles in the catalytic layer. Eventually the CO2 dissolved in catholyte and then was taken away into the liquid storage tank.GF was doped with nitrogen using urea, ammonium bicarbonate and ammonia water respectively. The nitrogen content of nitrogen doped GF prepared through those three methods was researched as well as the improvement of electrochemical performance and the influence on morphology and crystal structure. The results showed that nitrogen content and electrochemical performance of the nitrogen doped GF prepared through urea were optimal, the nitrogen doped GF prepared through ammonium bicarbonate taken second place, and the nitrogen doped GF prepared through ammonia water was the worst. The best temperatures and time of those methods were 700 ??10 h, 200 ??10 h and 180 ??15 h respectively. Pyrrol-like nitrogen was the main reason of the improvement of catalytic activity of nitrogen doped GF toward the redox reaction of Fe2+/Fe3+.GF was treated by hydrothermal method at 180 ? with different concentration of boric acid solution. The element composition of treated GF was researched as well as the improvement of electrochemical performance and the influence on morphology and crystal structure. The result of X-ray photoelectron spectroscopy showed that the boron atom did not dope into GF after hydrothermal treatment. While the nitrogen content of treated GF increased. The results of discharge tests of the cells and electrochemical tests of boron doped GF showed that the electrochemical activity of treated GF had been greatly improved and the results of physicochemical characterizations indicated that there was no change of crystal structure and morphology of GF in the process of hydrothermal treatment. The best concentration of boric acid solution and the best time of hydrothermal treatment was 0.04 g·m L-1 and 18 h. GF was treated through thermal annealing in the presence of boron acid under different temperatures for 4 h. And 1200 ? was the best temperature.