Hunault Myrtille O J Y, Khan Wilayat, Minár Jan, Kroll Thomas, Sokaras Dimosthenis, Zimmermann Patric, Delgado-Jaime Mario U, de Groot Frank M F
Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterial Science, Utrecht University , 3584CG Utrecht, The Netherlands.
New Technologies-Research Center, University of West Bohemia , Univerzitni 8, 306 14 Plzeň, Czech Republic.
Inorg Chem. 2017 Sep 18;56(18):10882-10892. doi: 10.1021/acs.inorgchem.7b00938. Epub 2017 Sep 5.
Metal-metal charge transfer (MMCT) is expected to be the main mechanism that enables the harvesting of solar light by iron-titanium oxides for photocatalysis. We have studied FeTiO as a model compound for MMCT with 1s2pRIXS at the Fe K-edge. The high-energy resolution XANES enables distinguishing five pre-edge features. The three first well distinct RIXS features are assigned to electric quadrupole transitions to the localized Fe* 3d states, shifted to lower energy by the 1s core-hole. Crystal field multiplet calculations confirm the speciation of divalent iron. The contribution of electric dipole absorption due to local p-d mixing allowed by the trigonal distortion of the cation site is supported by DFT and CFM calculations. The two other nonlocal features are assigned to electric dipole transitions to excited Fe* 4p states mixed with the neighboring Ti 3d states. The comparison with DFT calculations demonstrates that MMCT in ilmenite is favored by the hybridization between the Fe 4p and delocalized Ti 3d orbitals via the O 2p orbitals.
金属-金属电荷转移（MMCT）有望成为铁钛氧化物用于光催化收获太阳光的主要机制。我们以FeTiO作为MMCT的模型化合物，利用Fe K边的1s2p共振非弹性X射线散射（RIXS）对其进行了研究。高能量分辨率X射线吸收近边结构（XANES）能够区分五个边前特征。前三个明显不同的RIXS特征被归因于向局域化Fe* 3d态的电四极跃迁，由于1s芯孔而向较低能量移动。晶体场多重态计算证实了二价铁的形态。阳离子位点三角畸变允许的局部p-d混合导致的电偶极吸收贡献得到了密度泛函理论（DFT）和晶体场多重态（CFM）计算的支持。另外两个非局部特征被归因于向与相邻Ti 3d态混合的激发Fe* 4p态的电偶极跃迁。与DFT计算的比较表明，钛铁矿中的MMCT受Fe 4p与离域Ti 3d轨道通过O 2p轨道杂化的青睐。
