纤维状多孔钙锰氧化物制备及其氧还原反应电催化活性

doi:10.15541/jim20160437

摘要/Abstract

摘要：

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。

关键词: 海藻酸钙纤维, 非贵金属催化剂, Ca2MnO4氧还原, 燃料电池

Abstract:

Calcium-manganese oxides (Ca-Mn-O) of layer-pervoskite Ca₂MnO₄ was firstly prepared by using calcium 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 Ca₂MnO₄as 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.

Key words: calcium alginate fibre, non-noble metal catalysts, Ca2MnO4 oxygen reduction, fuel cell

中图分类号:

TM912

曹朝霞, 丁延敏, 王志超, 毛新欣, 尹艳红, 杨书廷. 纤维状多孔钙锰氧化物制备及其氧还原反应电催化活性[J]. 无机材料学报, 2017, 32(5): 535-542.

CAO Zhao-Xia, DING Yan-Min, WANG Zhi-Chao, MAO Xin-Xin, YIN Yan-Hong, YANG Shu-Ting. Porous Calcium Manganese Oxide: Preparation and Electrocatalytic Activity of Oxygen Reduction Reaction[J]. Journal of Inorganic Materials, 2017, 32(5): 535-542.

图/表 10

图1 Ca-Mn-O材料的XRD图谱(a), 等温吸脱附曲线和孔径分布图(b)

Fig. 1 XRD patterns (a), adsorption-desorption isothermal and inset of pore size distribution curves (b) of Ca-Mn-O samples

图2 海藻酸钙纤维的SEM照片

Fig. 2 SEM images of calcium alginate fibre

图3 CMO-1(a, b)和CMO-2(c, d)样品的FE-SEM图片; CMO-1(e, f)的EDS分析结果

Fig. 3 FE-SEM images of CMO-1 (a, b) and CMO-2 (c, d); EDS results of CMO-1 (e, f)

图4 CMO-1(a~c)和CMO-2(d~f)的TEM和HRTEM照片

Fig. 4 TEM and HRTEM images of CMO-1(a-c) and CMO-2 (d-f)

图5 Ca-Mn-O材料的XPS图谱

Fig. 5 XPS spectra of Ca-Mn-O samples(a) CMO-1; (b) CMO-2

图6 在氮气饱和KOH中Ca-Mn-O材料的的循环伏安曲线

Fig. 6 CV curves of Ca-Mn-O samples in N2-saturated 0.1 mol/L KOH

图7 Ca-Mn-O材料和Pt/C的线性扫描伏安图(a), H2O2产率和电子转移数(b)

Fig. 7 LSVs of Ca-Mn-O samples and Pt/C (a), percentage of peroxide and electron transfer number at different potentials (b)

表1 Ca-Mn-O材料的电化学测试结果

Table 1 Summary of electrochemical results for the Ca-Mn-O series

Material	Crystallographic structures	E_onset/V	E_half/V	n	HO₂/%	I_s/(mA·cm^-2)(0.3 V)
CMO-1	Ca₂MnO₄	0.81	0.66	3.78	12-18	-6.03
CMO-2	CaMn₃O₆	0.86	0.68	3.84	9-15	-4.41
Pt/C	-	0.93	0.86	3.87	5-11	-6.38

图8 Ca-Mn-O材料在不同转速下的线性扫描伏安图

Fig. 8 LSVs of Ca-Mn-O samples at various rotation rates

图9 Ca-Mn-O材料和Pt/C催化剂上氧还原的计时电流曲线

Fig. 9 Chronoamperometric curves of Ca-Mn-O samples and Pt/C

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