摘要
用简单的化学方法制备了过渡金属(TM)壳聚糖水杨醛席夫碱配合物,然后以此配合物为金属源和N源、以硝酸预处理石墨为载体,经热处理后制备了过渡金属/氮掺杂石墨催化剂TM-N-C-t(TM=Co,Ni,Cu;t=200,400,600,800,1 000℃).以此催化剂为修饰剂制备了玻碳修饰电极,并用循环伏安法(CV)和旋转圆盘电极(RDE)伏安法研究了催化剂TM-N-C-t的电化学行为和电催化氧还原(ORR)的催化性能,催化剂的组成和结构采用TG,FT-IR,XRD,XPS等技术进行了表征.研究结果表明,催化剂TM-N-C-t对ORR均显示不同程度的催化活性,其中以1 000℃热处理的钴基催化剂Co-N-C-1000的催化活性最好,其活性已接近相同条件下的商用催化剂JM 20%Pt/C,催化活性位主要为Co—N—C.根据扩散控制的不可逆反应的循环伏安行为,计算得到了TM-N-C-t催化剂电催化ORR的动力学参数,并以此提出了氧还原催化反应的机理,在活性最好的催化剂Co-N-C-1000修饰电极上,氧气以4e转移途径被还原为水.
Non-noble transition metal and nitrogen doped carbon catalysts for oxygen reduction reaction( ORR)were recognized as one of the most promising to replace the traditional Pt-based catalyst with the high cost and scarcity. Graphite-supported transition metal( TM = Co,Ni Cu) complexes of chitosan-salicyiclaldehyde Schiff base( TM-CS-Sal) were synthesized by a simple chemical method,then heat-treated at 200,400,600,800 and 1 000℃ to optimize their activity for ORR. The effects of heat treatment temperature and the nature of metal on the electrocatalytic properties of the resulting catalysts TM-N-C-t( t = 200,400,600,800,1 000 ℃) were surveyed using cyclic voltammetry( CV). The catalysts TM-N-C-t all showed strong catalytic activity toward the ORR,but the Cobased catalyst at heat temperature of 1 000 ℃( Co-N-C-1000) yielded the best ORR activity,which was close to that of the commercial JM 20% Pt / C. Fourier Transform Infrared( FT-IR),X-ray diffraction( XRD),X-ray photoelectron spectroscopy( XPS),thermogravimetric and differential thermal analysis( TG-DTA) were used to characterize these catalysts in terms of their structure and composition. The characterizing results combined with catalytic activities showed that Co-N-C potentially might be the main catalytic active sites of the best electrocatalyst Co-NC-1000 and responsible for the ORR catalytic activity in alkaline electrolyte. In addition,cyclic voltammetry also was used to obtain the important kinetic parameters: overall ORR electron transfer number and electron transfer coefficiency. The overall electron transfer numbers for ORR catalyzed by the catalysts heat-treated at 800 and 1 000℃ of Co-N-C-t( 800,1 000 ℃) were determined to be 3. 44 and 4. 03,suggesting that the ORR catalyzed by CoN-C-t( 800,1 000 ℃) was mixture of 2- and 4-electron transfer pathways,dominated by a 4-electron transfer process. The results obtained from RDE voltammetry are consistent with those from cyclic voltammetry. Based on these measurements,a mechanism of ORR occurring i
出处
《分子催化》
EI
CAS
CSCD
北大核心
2014年第6期553-563,共11页
Journal of Molecular Catalysis(China)
基金
山西省自然科学基金:'碳载壳聚糖希夫碱金属配合物燃料电池阴极催化剂制备及电催化氧还原研究'(2013011012-1)
关键词
过渡金属/氮掺杂石墨
电催化
氧还原
动力学
催化活化位
transition metal and nitrogen doped graphite
electrocatalysis
oxygen reduction reaction
kinetics
catalytic active sites
