X-ray
absorption spectroscopy is a powerful tool for the characterization
of local atomic structure. Commonly, bond lengths and coordination
numbers are extracted from the extended energy region of the spectrum
(extended X-ray absorption fine structure, EXAFS). However, for many
diluted systems, such as homogeneous catalysts, with a low concentration
of the active component and under in situ or operando conditions, one cannot collect sufficient EXAFS
data for a quantitative analysis. Considering the case of a homogeneous
ruthenium-based catalyst, where the ligand surrounding the ruthenium
atoms can change from Br to CO depending on the reaction conditions,
we establish here an effective machine learning approach based on
the descriptor analysis of spectral features. After the training procedure,
the algorithm predicts both the ligand surrounding ruthenium and the
distances to Br and CO ligands. The prediction quality of the approach
was verified by means of a cross-validation procedure applied to the
mixture of compounds and was validated for experimental spectra of
reference RuBr3 and [RuBr2(CO)3]2 complexes. This work describes a practical route to improve
classical fingerprint analysis and linear combination fit by more
sophisticated data science algorithms.
This work establishes structure-property relationships in Ru-based catalytic systems for selective hydrodeoxygenation of ketones to alkenes by combining extensive catalytic testing, in situ X-ray absorption spectroscopy (XAS) under high pressures...
Photocatalytic hydrogen (H2) production is a promising route for alternative energetics. Understanding structure–activity relationships is a crucial step towards the rational design of photocatalysts, which requires the application of operando spectroscopy under relevant working conditions. We performed an operando investigation on a catalytic system during the photodeposition of Pt on TiO2 and photostimulated H2 production, using simultaneous laboratory X-ray absorption spectroscopy (XAS), UV–Vis spectroscopy, and mass spectrometry. XAS showed a progressive increase in Pt fluorescence for Pt deposited on TiO2 for over an hour, which is correlated with the signal of the produced H2. The final Pt/TiO2 catalyst contained Pt(0) particles. The electronic features corresponding to the Pt4+ species in the UV–Vis spectrum of the solution disappear as soon as UV radiation is applied in the presence of formic acid, which acts as a hole scavenger, resulting in the presence of Pt(0) particles in solution.
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