一维锰基氧化物/氧化石墨烯的晶相结构对氧还原性能的影响

Preparation of one dimensional manganese-based oxides/graphene oxide composites and influence on the performance for oxygen reduction reaction

基于氧化石墨烯(graphene oxide,GO),以不同的锰源为原料,采用一步水热法合成两种不同晶相的锰基氧化物与GO的复合材料。样品分别经XRD、Raman、SEM及TEM进行结构、形貌表征。XRD测试结果表明合成的锰基氧化物分别为β-MnO_2和γ-MnOOH。Raman结果证明样品中GO的存在。SEM和TEM结果显示氧化物均为棒状结构,与GO复合后,形成了β-MnO_2/GO,γ-MnOOH/GO异相结构。循环伏安和旋转圆盘电极测试结果表明β-MnO_2/GO具有更为优异的氧还原催化活性,起始电位为-0.10 V(vs Hg/Hg O)。比较两种复合物,在-0.3 V(Hg/Hg O)电位下,β-MnO_2/GO具有比γ-MnOOH/GO更高的电流密度,这归因于β-MnO_2特别的晶相结构对氧还原的催化活性以及β-MnO_2和GO间优异的协同作用。这种新型β-MnO_2/GO复合材料有望成为一种价格低廉且高效的非贵金属氧还原催化剂。

Herein,we report a kind of one dimensional manganese oxides/Graphene oxide(GO)composites as ORR catalysts,and the effect of crystal phase on the performance for ORR was investigated and discussed.Specifically,GO was prepared by a modified Hummers method and the manganese-containing compounds with GO were prepared by a facile one-step hydrothermal method,showing higher activity for the ORR in alkaline electrolytes.The results confirmed that one dimensional manganese compound(β-MnO 2/GO)not only possessed large specific surface area but also could be well dispersed on the surface of GO.Cyclic voltammetry and rotating disk electrode test indicated thatβ-MnO 2/GO exhibited remarkable activity for oxygen reduction reaction.The composite exhibited considerable ORR performance with onset potential of-0.10 V(vs.Hg/HgO).Besides,theβ-MnO 2/GO presented a dominant four-electron pathway and higher current density than that ofγ-MnOOH/GO,which can be attributed to the special crystalline phase ofβ-MnO 2.The present approach is of high potential in preparing non-precious metal electrocatalysts with high ORR activity.