首次以海藻酸钙纤维为载体制得层状-钙钛矿结构的Ca2MnO4钙锰氧化物(Ca-Mn-O),并以尖晶石结构的CaMn3O6为对比样,测试了样品作为电化学氧还原催化剂(ORR)的性能.通过XRD、FE-SEM、TEM和BET对材料进行表征,结果表明该层状-钙钛矿结构的氧化物具有内部相互交联的多孔网状结构和大的比表面积.电催化测试结果表明:Ca2MnO4氧化物具有明显的催化活性,高的极限扩散电流密度、接近四电子氧化还原以及在碱性溶液中较低产率的过氧化氢,说明这种廉价而丰富的ORR催化剂具有潜在的应用前景.Ca-Mn-O氧化物的催化活性(初始还原电位、极限电流密度以及电子转移数)很大程度依赖于表面Mn的氧化态和晶体结构.此外,大的比表面积和多孔网状结构,增多了氧还原反应的电催化活性位;高的氧空位浓度有利于氧还原反应的进行;合适的晶体结构具有开放的空间,有利于氧的吸附.
Calcium-manganese oxides (Ca-Mn-O) of layer-pervoskite Ca2MnO4 was firstly prepared by using cal cium alginate fiber as supporter and then investigated as electrocatalysts for oxygen reduction reaction (ORR),compared with post-spinel CaMn3O6.The results of XRD,FE-SEM,TEM and BET displayed the as-synthesized layer-pervoskite Ca2MnO4 displayed interconnected porous network structure and high special surface area.The catalyst demonstrates significant electrocatalytic activity towards ORR:a high limit current density,near an apparent quasi four electron oxygen reduction,and low yield of peroxide species in alkaline solutions,which suggestes the potential application of Ca2MnO4 as cheap and abundant ORR catalysts.The catalytic activities of Ca-Mn-O oxides (onset potential,limiting current density and transferred electron number) depend strongly on the surface Mn oxidation state and the crystallographic structures.In addition,high specific surface area and porous network structure increase electrocatalytic activity sites of ORR,high concentration of oxygen vacancies favor process of ORR,appropriate crystallographic structures with open tunnels,facilitating oxygen chemisorption.
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