Li Xiaoning, Sun Yanhua, Wu Qingmei, Liu Huan, Gu Wen, Wang Xiaolin, Cheng Zhenxiang, Fu Zhengping, Lu Yalin
Institute for Superconducting & Electronic Materials (ISEM), Australia Institute for Innovation Materials, Innovation Campus , University of Wollongong , Squires Way , North Wollongong NSW 2500 , Australia.
Chinese Academy of Sciences (CAS) Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering , University of Science and Technology of China , Hefei 230026 , P.R. China.
J Am Chem Soc. 2019 Feb 20;141(7):3121-3128. doi: 10.1021/jacs.8b12299. Epub 2019 Feb 6.
The composition and structure are crucial for stabilizing an appropriate electronic configuration (unit e electron for example) in high-efficiency electrocatalysts for the oxygen evolution reaction (OER). Here, an excellent platform to investigate the roles of the composition and structure in tuning the electron configuration for higher OER efficiency is provided by layered perovskite oxides with subtle variations of composition and structure (doping with 0%, 50%, and 100% cobalt in the BiFeTiO). The crystal structures were analyzed by X-ray diffraction refinement, and the electronic structures were calculated based on X-ray absorption spectroscopy and magnetization vs temperature plots according to the Curie-Weiss law. The results indicate that the elongation of oxygen octahedra along the c-axis in layered perovskite could stabilize Co ions in the intermediate spin (IS) ( t)( e) state, resulting in dramatically enhanced electronic conductivity and absorption capacity. Subsequently, the OER efficiency of sample with 100% Co was found to be (incredibly) 100 times higher than that of the sample with 0% Co, with the current density increased from 0.13 to 43 mA/cm (1.8 V vs reversible hydrogen electrode); the Tafel slope was reduced from 656 to 87 mV/dec; and double-layer capacity enhanced from 174 to 4193 μF/cm. This work reveals that both the composition and structure should be taken into account to stabilize a suitable electronic structure such as IS Co ions with moderate absorption and benign electronic conductivity for high-efficiency catalysis of the OER.
对于析氧反应（OER）的高效电催化剂而言，其组成和结构对于稳定合适的电子构型（例如单位e电子）至关重要。在此，具有组成和结构细微变化（在BiFeTiO中钴掺杂量为0%、50%和100%）的层状钙钛矿氧化物提供了一个极佳的平台，用于研究组成和结构在调节电子构型以提高OER效率方面的作用。通过X射线衍射精修分析晶体结构，并根据居里 - 外斯定律基于X射线吸收光谱和磁化强度与温度关系图计算电子结构。结果表明，层状钙钛矿中氧八面体沿c轴的伸长可使Co离子稳定在中间自旋（IS）(t)(e)状态，从而显著提高电子导电性和吸收能力。随后发现，100% Co样品的OER效率（令人难以置信地）比0% Co样品高100倍，电流密度从0.13增加到43 mA/cm²（相对于可逆氢电极1.8 V）；塔菲尔斜率从656降低到87 mV/dec；双层电容从174增强到4193 μF/cm²。这项工作表明，为了稳定合适的电子结构（如具有适度吸收和良好电子导电性的IS Co离子）以实现OER的高效催化，应同时考虑组成和结构。
