以尿素为含氮前躯体,通过热转化法制备了质子交换膜燃料电池(PEMFC)氧还原催化剂 Co-N-C及Co-Ti-N-C,考察了不同的尿素/金属比(R)、焙烧温度及钛含量等条件对 Co-N-C 及 Co-Ti-N-C 电催化剂氧还原催化活性和稳定性的影响.利用元素分析、热重、X射线衍射分析、X射线光电子能谱等方法对催化剂进行了表征,研究了催化剂的氧还原活性中心结构.结果表明,催化剂在热处理温度为800℃,尿素与金属Co的摩尔比 R＝12时的氧还原性能最佳,峰电位(Ep,c )达到0．142 V (vs．SCE).催化剂 Co-N-C 经353 K硫酸溶液浸泡3 d 后,催化剂 Co-N-C 的活性中心Co4 N 的含量增大,Ep,c正移至0．445 V(vs．SCE).钛的掺杂没有改变催化剂的活性中心结构,明显提高了其在酸性介质中的稳定性.
In this work,a proton exchange membrane fuel cell (PEMFC)oxygen reduction catalyst Co-N-C and Co-Ti-N-C was prepared by thermal conversion using urea as nitrogen precursor.The oxygen reduction perform-ance and stability of catalyst Co-N-C and Co-Ti-N-C was researched with different urea/Co molar ratios(R),dif-ferent calcination temperature and different titanium content.Co-N-C and Co-Ti-N-C were characterized by ele-mental analysis,thermal gravimetric,X-ray diffraction and X-ray photoemission spectroscopy,and the structure of the oxygen reduction active center was researched.The results showed that the best oxygen reduction per-formance of the catalyst was in the heat treatment temperature 800 ℃,urea/Co molar ratios R=12,the peak potential (Ep,c)reached 0.142 V (vs.SCE).After soaking for three days in the 353 K sulfuric acid solution,the content of the catalyst active center Co4 N was increased,Ep,c was moved to 0.445 V.The doping of titanium didn’t change the structure of the oxygen reduction active center,but obviously improved the stability of the catalyst in the acid medium.
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