Department of Chemical and Petroleum Engineering and Department of Chemistry, University of Kansas, Lawrence, KS 66045, USA.
Department of Chemistry and Chemical Engineering, Beijing University of Technology, Beijing, 100080, China.
Chem Soc Rev. 2017 Apr 3;46(7):2001-2027. doi: 10.1039/c6cs00931j.
Chemistry of a catalyst surface during catalysis is crucial for a fundamental understanding of mechanism of a catalytic reaction performed on the catalyst in the gas or liquid phase. Due to the pressure- or molecular density-dependent entropy contribution of gas or liquid phase of the reactants and the potential formation of a catalyst surface during catalysis different from that observed in an ex situ condition, the characterization of the surface of a catalyst under reaction conditions and during catalysis can be significant and even necessary for understanding the catalytic mechanism at a molecular level. Electron-based analytical techniques are challenging for studying catalyst nanoparticles in the gas or liquid phase although they are necessary techniques to employ. Instrumentation and further development of these electron-based techniques have now made in situ/operando studies of catalysts possible. New insights into the chemistry and structure of catalyst nanoparticles have been uncovered over the last decades. Herein, the origin of the differences between ex situ and in situ/operando studies of catalysts, and the technical challenges faced as well as the corresponding instrumentation and innovations utilized for characterizing catalysts under reaction conditions and during catalysis, are discussed. The restructuring of catalyst surfaces driven by the pressure of reactant(s) around a catalyst, restructuring in reactant(s) driven by reaction temperature and restructuring during catalysis are also reviewed herein. The remaining challenges and possible solutions are briefly discussed.
催化剂表面在催化过程中的化学性质对于深入理解在气相或液相中进行的催化反应的机理至关重要。由于反应物的气相或液相中存在压力或分子密度依赖性的熵贡献，以及在催化过程中可能形成不同于原位条件下观察到的催化剂表面，因此在反应条件下和催化过程中对催化剂表面进行表征对于在分子水平上理解催化机制可能具有重要意义，甚至是必要的。尽管电子基分析技术是研究气相或液相中催化剂纳米粒子所必需的技术，但它们在研究中具有挑战性。这些电子基技术的仪器设备和进一步发展现在已经使得原位/操作条件下的催化剂研究成为可能。在过去的几十年中，人们对催化剂纳米粒子的化学和结构有了新的认识。本文讨论了催化剂的原位/操作条件研究与原位研究之间的差异的根源，以及在反应条件下和催化过程中对催化剂进行表征所面临的技术挑战以及相应的仪器设备和创新，讨论了催化剂表面在反应物（s）压力下的重构、由反应温度驱动的反应物（s）中的重构以及在催化过程中的重构。本文还简要讨论了剩余的挑战和可能的解决方案。
