Simböck Johannes, Ghiasi M, Schönebaum Simon, Simon Ulrich, de Groot Frank M F, Palkovits Regina
Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
Center for Automotive Catalytic Systems Aachen, RWTH Aachen University, Aachen, 52074, Germany.
Nat Commun. 2020 Jan 31;11(1):652. doi: 10.1038/s41467-020-14305-0.
Perovskite-type transition metal (TM) oxides are effective catalysts in oxidation and decomposition reactions. Yet, the effect of compositional variation on catalytic efficacy is not well understood. The present analysis of electronic characteristics of B-site substituted LaCoO derivatives via in situ X-ray absorption spectroscopy (XAS) establishes correlations of electronic parameters with reaction rates: TM t and e orbital occupancy yield volcano-type or non-linear correlations with NO oxidation, CO oxidation and NO decomposition rates. Covalent O 2p-TM 3d interaction, in ultra-high vacuum, is a linear descriptor for reaction rates in NO oxidation and CO oxidation, and for NO decomposition rates in O presence. Covalency crucially determines the ability of the catalytically active sites to interact with surface species during the kinetically relevant step of the reaction. The nature of the kinetically relevant step and of surface species involved lead to the vast effect of XAS measurement conditions on the validity of correlations.
钙钛矿型过渡金属（TM）氧化物是氧化和分解反应中的有效催化剂。然而，成分变化对催化效率的影响尚未得到充分理解。通过原位X射线吸收光谱（XAS）对B位取代的LaCoO衍生物的电子特性进行的当前分析建立了电子参数与反应速率之间的相关性：TM t和e轨道占有率与NO氧化、CO氧化和NO分解速率呈现火山型或非线性相关性。在超高真空下，共价O 2p-TM 3d相互作用是NO氧化和CO氧化反应速率以及O存在时NO分解速率的线性描述符。共价性在反应的动力学相关步骤中至关重要地决定了催化活性位点与表面物种相互作用的能力。动力学相关步骤的性质以及所涉及的表面物种导致XAS测量条件对相关性有效性产生巨大影响。
