3D flowerlike α-nickel hydroxide with enhanced electrochemical activity synthesized by microwave-assisted hydrothermal method
3D flowerlike α-nickel hydroxide with enhanced electrochemical activity synthesized by microwave-assisted hydrothermal method
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DOI：
10.1021/cm702207w
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发表时间：
2008-01-08
影响因子：
8.6
通讯作者：
Suib, Steven L.
中科院分区：
文献类型：
--
作者：
Xu, Linping;Ding, Yun-Shuang;Suib, Steven L.
氢氧化镍已经受到越来越多的关注，特别是由于其电化学性质和在可再充电Ni基碱性电池中的潜在应用，Ni/Cd、Ni/Zn和Ni/MH。Ni（OH）2具有六方层状结构，具有两种多晶型物，α-和β-Ni（OH）（2）。α-Ni（OH）（2）的电化学性能优于β-形式。采用微波辅助水热法制备了层间距为7.0埃的纳米花状α-氢氧化镍材料。XRD和FF-IR测试结果表明，该方法制备的Ni（OH）（2）样品具有典型的α相结构。FE-SEM图像显示出许多均匀的花状结构，直径为700 nm-1 μ m，由聚集的薄片组成。TEM结果表明，薄片由许多直径为2 - 3 nm的纳米晶体组成。采用热重分析和程序升温脱附（TPD）研究了其热稳定性和升温过程中的气体析出。α-氢氧化镍在450 ℃煅烧后转变为具有立方晶体结构的NiO; NiO仍保持α-Ni（OH）（2）的形态。循环伏安法用于测定Ni（OH）（2）电极在1M KOH中的电化学性质。结果表明，MW-HT法制备的α-Ni（OH）（2）对O-2的电化学还原具有最好的电化学活性，而常规HT法制备的α-Ni（OH）（2）和β-Ni（OH）（2）对O-2的电化学还原活性最低。研究了镍源和沉淀剂对产物物相和形貌的影响。采用常规水热法研究了微波辐射的作用。在此讨论了可能的生长机制。循环伏安实验表明，H_2O_2在α-Ni（OH）_2电极上可被还原为OH~-。Levich方程被用来计算O-2氧化还原反应过程中转移的电子数。
Nickel hydroxide has received increased attention especially due to its electrochemical properties and potential applications in rechargeable Ni-base alkaline batteries, e.g., Ni/Cd, Ni/Zn, and Ni/MH. Ni(OH)2 has a hexagonal layered structure with two polymorphs, alpha- and beta-Ni(OH)(2). alpha-Ni(OH)(2) shows superior electrochemical properties compared to those of the beta-form. Nanosized flowerlike alpha-nickel hydroxide materials with an interlayer spacing of 7.0 angstrom have been prepared by a microwave-assisted hydrothermal method. The experimental results from XRD and FF-IR showed that the Ni(OH)(2) sample prepared by this method had the typical alpha-phase. FE-SEM images showed many uniform flowerlike architectures with diameters of 700 nm-1 mu m which consisted of the aggregated flakes. TEM results showed the flakes were built up from many nanocrystals with 2-3 nm diameters. TGA and TPD were employed to investigate thermal stability and gas evolution during the heating process. alpha-Nickel hydroxide was transferred to NiO with a cubic crystalline structure after being calcined at 450 degrees C; the NiO still kept the morphology of alpha-Ni(OH)(2). Cyclic voltammetry was used to determine the electrochemical properties of the Ni(OH)(2) electrode in 1 M KOH. alpha-Ni(OH)(2) prepared by MW-HT had the best electrochemical activity for the electrochemical reduction of O-2 compared with alpha-Ni(OH)(2) synthesized by conventional HT methods and beta-Ni(OH)(2). The effects of nickel sources and precipitators on the phase and morphology of the products were studied. Conventional hydrothermal methods were used to study the role of microwave irradiation. The possible growth mechanism is discussed here. The CV experiments showed that H2O2 can be reduced to OH- on the alpha-Ni(OH)(2) electrode. The Levich equation was used to calculate the number of electrons transferred during the O-2 redox reaction.