氮掺杂石墨烯的制备及氧还原电催化性能

Synthesis of Nitrogen-doped Graphene and Its Electrocatalytic Performance Toward Oxygen Reduction Reaction

采用两步热解法,用尿素掺杂氧化石墨烯(GO)得到N掺杂的还原氧化石墨烯(N-RGO),通过控制反应温度,制备了具有不同电催化活性的N掺杂的还原氧化石墨烯.透射电子显微镜(TEM)和扫描电子显微镜(SEM)结果显示,制得的氮掺杂石墨烯(nG)表面褶皱和重叠增加.X射线光电子能谱(XPS)证明,氮元素以吡啶N、吡咯N和石墨化的N 3种形式掺杂在石墨烯中,最高摩尔分数为6.6%.通过循环伏安(CV)和旋转圆盘电极(RDE)测试了nG的电化学性能,结果表明,在酸性电解质中对氧还原(ORR)有较高的催化活性,起始电位在0.1 V左右,电催化还原氧气时主要为四电子反应,且相对商用的Pt/C催化剂有更好的电化学稳定性,其中第一步热解温度为200℃制得的nG催化性能最好.

A series nGs with different electrocatalytic abilities toward oxygen reduction reaction （ORR） was prepared via a two-steps pyrolysis method by controlling the reaction temperature on the physical mixture of graphene oxideand urea. Transmission electron microscopy and scanning electron microscopy display nG with highly wrinkled and overlapping structures. X-ray photoelectron spectroscopy shows that nitrogen is successfu- lly doped in graphene with the formation of pyridinic N, pyrrolic N and graphitic N, and the maximum nitro- gen content is 6.6% （ molar fraction）. Cyclic vohammogram and rotating disk electrode measurement show that nGs exhibit high electrocatalytic activity with an onset potential of 0. 1 V in an acid electrolyte. Moreover, the nGs catalyzed oxygen reduction revealed a favorable formation of water via a four-electron pathway and excellent stability over Pt/C catalyst. Furthermore, the nG obtained at 200 ~C in the first pyrolysis step dis- plays the best catalytic perfor-mance.