Co/MR氮掺杂炭气凝胶的制备、结构及氧还原性能

Synthesis of Co-loaded carbon aerogels for oxygen electro-reduction

以三聚氰胺、间苯二酚、甲醛为原料，采用溶胶一凝胶法、冷冻干燥等步骤制备出三聚氰胺-间苯二酚一甲醛（MR）干凝胶；并以所制炭气凝胶为载体浸渍硝酸钴，经氮气中高温炭化，得到钴复合氮掺杂的炭气凝胶。考察间苯二酚和三聚氰胺比例、凝胶pH值及炭化条件等对气凝胶结构和催化氧还原活性的影响，采用XRD、XPS、低温氮气吸脱附等方法研究催化剂的结构。随pH值增加，MR气凝胶的介孔分布向小孔移动；当M／R物质的量比为6：1时，其介孔分布为3．0—4．0nm。钴复合炭气凝胶多孔结构中存在均匀分布Co金属颗粒和管状炭，Co金属颗粒粒径随炭化温度升高而增加。采用旋转圆盘电极研究催化剂在0．5mol／LH2SO4溶液中的电化学性能，结果表明催化剂具有良好的氧还原活性。

Melamine-resorcinol-formaldehyde （MR） aerogels were prepared by the sol-gel polymerization of formaldehyde with melamine and resorcinol using NaOH as catalyst, followed by freeze-drying. Co-loaded carbon aerogels were obtained by impregna- ting the MR aerogels with Co（III） tert-butanol solution, followed by carbonization in N2. The effects of the molar ratios of mela- mine to resorcinol （ M/R）, pH, Co content and carbonization temperature on the microstructure of the aerogels were investigated. It was found that the microstructure of the MR aerogels could be adjusted by the M/R ratio and pH. The mesopore size of the MR aer- ogels decreased with increasing pH and the mesopore size was in the range of 3-4nm when the M/R was 6：1. There were some gra- phitic nano-ribbons in Co-loaded carbon aerogels. The metal average particle size in the carbon aerogels increased from 5.2 to 6.2 nm when the carbonization temperature was increased from 700 to 900 ℃. The electrochemical properties of the Co-loaded car- bon aerogels as catalysts in the oxygen reduction reaction were evaluated by a rotating disc electrode technique in an O2-saturated 0.5 mol/L H2SO4 solution, and the catalysts showed a good electrocatalytic activity for the reaction.