Thermal Decomposition of Nickel Oxalate Dihydrate: A Detailed XPS Insight,The Journal of Physical Chemistry C

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Thermal Decomposition of Nickel Oxalate Dihydrate: A Detailed XPS Insight
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-12-17 , DOI: 10.1021/acs.jpcc.9b07879
Sergey Chenakin _{1,

2} , Norbert Kruse _{1,

3}

Affiliation

X-ray photoelectron spectroscopy (XPS) was employed to study the thermal decomposition in vacuum of nickel oxalate dihydrate. The process is shown to proceed via mainly two stages. Evaluating the high-resolution core-level spectra, Auger and valence band spectra acquired as a function of temperature up to 500 °C allowed changes in the surface composition, electronic structure, and chemical state of atoms in the oxalate to be monitored continuously. In particular, the removal of crystallization water in the dehydration stage was found to affect the Ni-related XPS characteristics such as the O/Ni atomic ratio, full width at half-maximum of the Ni 2p_3/2 and Ni LMM peaks, Ni 2p_3/2 binding energy, satellite-to-Ni²⁺ peak intensity ratio, and the Ni Auger parameter, all of which demonstrated local maxima at ∼200 °C, which is the temperature corresponding to the highest rate of dehydration. XPS analysis of the product formed in the decomposition stage at ∼350 °C revealed, in addition to metallic Ni as a major constituent, an intermediate oxygen-deficient phase with a stoichiometry corresponding to NiC₂O₃ or/and Ni₂C₄O₇. The final product of Ni oxalate decomposition at temperatures above 400 °C was found to be metallic Ni particles partially covered with surface oxide NiO, chemisorbed oxygen atoms, and graphitic/amorphous carbon. The XPS studies were complemented by traditional X-ray diffraction, thermogravimetry, and differential thermal analysis coupled with mass spectrometry.

中文翻译：

二水合草酸镍的热分解：详细的XPS见解

用X射线光电子能谱（XPS）研究了草酸镍二水合物在真空中的热分解。该过程主要通过两个阶段进行。通过评估高分辨率的核心能级光谱，获得的俄歇和价带光谱作为温度高达500°C的函数，可以连续监测草酸盐中原子的表面组成，电子结构和化学状态的变化。特别地，发现在脱水阶段除去结晶水会影响Ni相关的XPS特性，例如O / Ni原子比，Ni 2p _3/2的半峰全宽和Ni LMM峰，Ni 2p _3/2结合能，卫星至Ni ²⁺峰值强度比和Ni Auger参数，所有这些都在〜200°C处表现出局部最大值，这是与最高脱水速率相对应的温度。在〜350°C的分解阶段形成的产物的XPS分析表明，除了金属Ni作为主要成分外，中间氧不足相的化学计量比还对应于NiC ₂ O ₃或/和Ni ₂ C ₄ O ₇。草酸镍在高于400°C的温度下分解的最终产物是金属Ni颗粒，部分被表面氧化物NiO，化学吸附的氧原子和石墨/无定形碳覆盖。XPS研究得到了传统X射线衍射，热重分析，差热分析和质谱分析的补充。

更新日期：2019-12-18

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