Performiance of air－breathing directmethanol fuel cell with Au－coated aluminum current collectors

Zhenyu Yuan

Yufeng Zhang

Jiaxing Leng

Youran Zhao

Xiaowei Liu

Abstract

Current collectors of the direct methanolfuel cell （DMFC） are of significant importance for portable power sources， andgreatly determine the weight energy density and cost of the cell． In thispaper， the air－breathing aluminum （Al） current collectors have been developedfor powering portable applications． Theanode and cathode current collectors with the area of 4．5 cm2 were fabricatedon the Al substrates utilizing Computer Numerical Control （CNC） technology．To obtain strong anti－corrosion resistance， a 3－μm－Au layer was deposited on the current collectors using chemicalplating． Compared with the graphite and stainless steel， thecharacterization of the Au－coated Al current collector was investigated toexhibit superior characteristics in electricconductivity， weight and electrochemical corrosion resistance． The currentcollector was applied to a DMFC and the cell performance was experimentallyinvestigated under different operating conditions． The measured maximum powerdensity of the DMFC could reach 19．8 mW cm−2 at current density of 98 mA cm−2with 2 M methanol solutions． The results indicated that the Au－coated Alcurrent collectors presented in this paper might be helpful for the developmentof portable power sources applied in future commercial applications．

Table 1 e Comparison of properties among  Graphite， Stainless steel and Aluminum．

the layer of Ni／P between Al and Au coatingmaking the combination between coating and Al substrate more compactly， and thecoating would not fall off the substrate result from the mechanical package andelectrochemical corrosion．

Ni／P coating between Al current collector andAu layer could prevent electrochemical corrosion effectively， because the Alexhibited large potential difference with Au and it is easily to take electrochemicalcorrosion when the Au layer coated directly on Al substrate． Moreover， Ni／Player

could cover the pin－hole of the Al currentcollector compactly， which enhanced the binding force， prevented Au layer separatedfrom Al substrate．

实验部分没说用的什么铝，是纯铝还是铝合金。

Table 2 e The test report of XRAY  thickness measure system．

表格中的C．O．V．指的是coefficient of variation，变异系数

以上三幅图取自中国大百科全书第二版

Fig． 2 e The Au－coated Al－based DMFC： （a）  schematic of the single cell design； （b） real features of the assembled DMFC．

Fig． 3 e TAFEL curves for Al with and  without Au layer after 15 days．

simulated DMFC environments with 1 M H 2 SO4 solutions at 60 C

The corrosion current density was 0．676＊10－5mA cm－2

Fig． 4 e Potential dynamic polarization  of Au－coated Al

没太理解全文中15天的意思，看上去是指OCV的曲线

Fig． 5 e SEM images of the surface of the  channels after electrochemical corrosion．

Fig． 6 e Contact resistance curves of the  DMFC with different assembly pressure．

Fig． 7 e The water contact angle of  different current collector materials： （a） aluminum； （b） stainless steel； （c）  graphite．

Fig． 8 e Performance curves of the DMFC  with different methanol concentrations．

Fig． 9 e Power density curves of the DMFC  at different anode flow rates．

Fig． 10 e The performance of single fuel  cell when the temperature increased from 25 to 65C．

Fig． 11 e Polarization curves for  Au－coated Al and graphite．

Fig． 12 e Working stability testing of  cell performance with different current collectors．

The reason might be that due to the hydrophilefeature of graphite， more water accumulated on

the surface， and this phenomenon wouldblock the oxygen channel into cathode side．The water flooding would appear to reducethe oxygen mass transport and the performance with a certain extent．The declineof performance indicates that the gradual accumulation of water at the cathodeside have reverse effects on the air－breathing DMFCs for a long operation．

这里没有讲为什么用金的集流体电流也会同样下降。原文的解释有些牵强。

Conclusion

In this work， the Au－coated Al current  collector was applied to the air－breathing DMFC． By comparison with graphite  and stainless steel， Au－coated Al represented superior material characteristics  of electrical contact resistance，  water contact angle and weight for the DMFC． Furthermore， the experimental  investigation results show that the concentration of methanol and the operating temperature affect the DMFC performance markedly． Then， we made  a comparison of the performance  between Au－coated Al and graphite under the same conditions， Au－coated Al current collector can yield better performance （19．8 mW cm－2 of  peak power density） than graphite  （16．34 mW cm－2 ）， and the performance is very steadily， verifying the feasibility of Au－coated Al as the material for DMFC current collector  in commercialization development．  Moreover， the batch production of Al current collector can greatly reduce the weight of the stack and cost．

Therefore， the investigation on Al  current collector in this work can provide some guidance for portable  applications．