Optimization of structure and design of membrane electrode assembly for DMFC

通过在电极/电解质界面上采用溅射技术添加Pt薄膜，成功地实现了功率输出的30%的增强。在阳极界面上进行Pt-Ru二元溅射的类似方法，并且二元催化剂的最佳组成以及用于更高功率输出的最佳量也是明确的。结果表明，DMFC的输出功率为0.22W/cm ^2。在此基础上，设计并制备了阴极和阳极分别为Pt和Pt-Ru黑催化剂的致密催化剂薄层，成功地实现了输出功率高达0.35W/cm ^2的DMFC。通过采用多孔碳板的新型电极结构，成功地实现了甲醇穿透率降低到1/3-1/10。以Nafion 117和112为膜电极，研究了甲醇渗透与温度、甲醇浓度和电流密度的关系，并在此基础上提出了甲醇渗透的经验计算公式。作为一种新型的高温、200℃、低湿固体电解质，用离子液体浸渍的Nafion，MPPTFSI等，并成功地制备了具有NASICON型结构的含质子无机化合物。前者在200℃时的电导率为10^<-2>Scm^<-1>，为质子导电型。成功地获得了尺寸为几纳米且高度分布在介孔碳颗粒表面的细颗粒。

30% enhancement in power output was successfully achieved by an employment of Pt thin film addition on to the electrode/electrolyte interface with a sputtering technique. The similar approach was conducted with Pt-Ru binary sputtering on the anode interface, and an optimum composition of the binary catalyst and also the optimum amount for higher power output were made clear. As a result of these investigations, DMFC power output with 0.22W/cm^2 was achieved. A condensed catalyst thin layer with Pt and Pt-Ru black catalyst on cathode and anode, respectively, was designed and prepared based on the above investigations, and we could successfully demonstrated a DMFC with a power output as high as 0.35W/cm^2.By employing a novel electrode structure with a porous carbon plate, reduction of the methanol crossover to 1/3-1/10 was successfully attained. And then, it made DMFC operation with high concentration methanol like 15-17M possible.For a practical MEA using Nafion 117 and 112, methanol crossover as a function of temperature, methanol concentration and current density was evaluated, and based on this, an empirical equation to calculate methanol crossover was proposed.The anode overvoltage was successfully reduced by the addition of TiO2, 8%, to the catalyst layer.As a novel solid electrolyte for high temperature, 200℃, and low humidity, Nafion impregnated with an ionic liquid, i.e., MPPTFSI etc., and a proton-containing inorganic compounds with NASICON-type structures were successfully prepared. The former showed electric conductivity 10^<-2> Scm^<-1> at 200℃, and suggested a proton conduction.A novel catalyst employing mesoporous carbon particles as support of Pt-Ru catalyst was prepared. It was succeeded to obtain fine particles with several nano-meter in size and highly distributed on the surface of the mesoporous carbon particles.