二元氧化物修饰催化剂的制备及其自增湿性能

Binary oxide modified catalyst preparation and self-humidifying performance

利用锡硅二元氧化物分别采用前修饰法和后修饰法修饰Pt/C催化剂,制备得到两种复合催化剂,并用于阳极催化层制备膜电极(MEA)。首先,考察修饰方式对膜电极性能的影响。膜电极的电池性能测试表明,使用前修饰法制备的Pt/SnO_(2)-SiO_(2)/C复合催化剂表现出更优的电池性能:在电池温度为50℃、完全增湿条件下,0.6 V的电流密度高达1100 mA/cm^(2)。同时该膜电极也显示出良好的自增湿性能和稳定性:在电池温度为50℃、完全不增湿(干气)条件下,0.6 V的电流密度为930 mA/cm^(2),且经过10 h稳定性测试后,性能仅降低13%,而空白膜电极在2 h内性能下降63%。进一步比较在不同相对湿度条件下的膜电极性能,结果表明该膜电极在相对湿度较低的条件下表现出优异的自增湿性能。根据实验数据,初步推测出一种使用Pt/SnO_(2)-SiO_(2)/C复合催化剂的膜电极的自增湿机理。

The Pt/C catalyst was modified by premodification and postmodification methods using tin-silicon binary oxide to prepare two composite catalysts.Furthermore,two composite catalysts were used on the anode to prepare a membrane electrode assembly(MEA).First,the influence of modification methods on the performance of MEA was investigated.The cell performance test of two MEAs demonstrated that the Pt/SnO_(2)-SiO_(2)/C composite catalyst prepared by the premodification method had better cell performance:the current density at 0.6 V is as high as 1100 mA/cm^(2) under complete humidification at 50℃.At the same time,the MEA also exhibited excellent self-humidification performance and stability:the current density at 0.6 V is 930 mA/cm^(2) at a 50℃cell temperature and with no humidification(dry gas);after the 10 h stability test,the performance only decreased by 13%,while the performance of blank MEAs decreases by 63%within 2 h.Further comparisons of the MEA performance under different relative humidity conditions shows that the MEA exhibits excellent selfhumidification performance under low relative humidity conditions.According to the experimental data,the self-humidification mechanism of a Pt/SnO_(2)-SiO_(2)/C composite catalyst is preliminarily speculated.