Zhang Mengyuan, Duan Xiaolan, Gao Ying, Zhang Shuangshuang, Lu Xiaoyan, Luo Kongliang, Ye Jian, Wang Xiaopeng, Niu Qiang, Zhang Pengfei, Dai Sheng
School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China.
ACS Appl Mater Interfaces. 2023 Oct 4;15(39):45774-45789. doi: 10.1021/acsami.3c07268. Epub 2023 Sep 23.
Tuning surface oxygen vacancies is important for oxide catalysts. Doping elements with different chemical valence states or different atomic radii into host oxides is a common method to create oxygen vacancies. However, the concentration of oxygen vacancies in oxide catalysts is still limited to the amount of foreign dopants that can be tolerated (generally less than 10% atoms). Herein, a principle of engineering the configurational entropy to tune oxygen vacancies was proposed. First, the positive relationship between the configuration entropy and the formation energy of oxygen vacancies () in 16 model oxides was estimated by a DFT calculation. To verify this, single binary oxides and high-entropy quinary oxides (HEOs) were prepared. Indeed, the concentration of oxygen vacancies in HEOs (O = 3.66) was higher compared to those of single or binary oxides (O = 0.22-0.75) by O XPS, O-TPD, and EPR. Interestingly, the reduction temperatures of transition metal ions in HEOs were generally lower than that in single-metal oxides by H-TPR. The lower of HEOs may contribute to this feature, which was confirmed by in situ XPS and in situ XRD. Moreover, with catalytic CO/CH oxidation as a model, the high-entropy (MnCuCoNiFe)O catalyst showed higher catalytic activity than single and binary oxides, which experimentally verified the hypothesis of the DFT calculation. This work may inspire more oxide catalysts with preferred oxygen vacancies.
调控表面氧空位对于氧化物催化剂至关重要。将具有不同化学价态或不同原子半径的元素掺杂到主体氧化物中是产生氧空位的常用方法。然而，氧化物催化剂中氧空位的浓度仍局限于可耐受的外来掺杂剂的量（通常小于10%原子）。在此，提出了一种通过工程化组态熵来调控氧空位的原理。首先，通过密度泛函理论（DFT）计算估计了16种模型氧化物中组态熵与氧空位形成能（）之间的正相关关系。为了验证这一点，制备了单一二元氧化物和高熵五元氧化物（HEOs）。实际上，通过氧X射线光电子能谱（O XPS）、氧程序升温脱附（O-TPD）和电子顺磁共振（EPR）可知，与单一或二元氧化物（O = 0.22 - 0.75）相比，HEOs中的氧空位浓度更高（O = 3.66）。有趣的是，通过氢程序升温还原（H-TPR）可知，HEOs中过渡金属离子的还原温度通常低于单一金属氧化物中的还原温度。HEOs较低的[此处原文缺失相关内容]可能促成了这一特性，原位XPS和原位XRD证实了这一点。此外，以催化CO/CH氧化为模型，高熵（MnCuCoNiFe）O催化剂表现出比单一和二元氧化物更高的催化活性，这从实验上验证了DFT计算的假设。这项工作可能会激发更多具有理想氧空位的氧化物催化剂。
