In situ formation of hydrides and carbides in palladium catalyst: When XANES is better than EXAFS and XRD

• Published in: Catalysis today Vol. 283; pp. 119 - 126
• Main Authors: Bugaev, Aram L., Guda, Alexander A., Lazzarini, Andrea, Lomachenko, Kirill A., Groppo, Elena, Pellegrini, Riccardo, Piovano, Andrea, Emerich, Hermann, Soldatov, Alexander V., Bugaev, Lusegen A., Dmitriev, Vladimir P., van Bokhoven, Jeroen A., Lamberti, Carlo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2017
• Subjects: EXAFS; Monte Carlo simulations; Palladium carbide; Palladium hydride; XANES simulations; XRPD; Palladium carbide; Monte Carlo simulations; XANES simulations; Palladium hydride; EXAFS; XRPD
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2016.02.065

[Display omitted] •Reversible hydride phase observed in Pd/C catalysts with EXAFS and XRPD.•Irreversible carbide phase observed in Pd/C catalysts with EXAFS and XRPD.•EXAFS and XRPD hardly discriminate Pd-hydrate from Pd-carbide.•XANES simulations easily discriminate Pd-hydrate from Pd-carbide.•The active PdHx (or PdCy) phase can be determined in operando conditions. In a number of hydrogenation reactions, palladium nanoparticles may undergo a transition to the hydride or the carbide phase, which affects the catalytic properties. In the current work, we determine the structural evolution of an industrial Pd/C catalyst in the presence of hydrogen and acetylene by means of in situ X-ray absorption spectroscopy and X-ray powder diffraction. We observe reversible hydride phase formation and irreversible formation of the carbide phase. The near-edge structure of the absorption spectra (XANES) plays the key role in distinguishing between hydride and carbide phases. We show that the presence of hydrogen and carbon atoms have a direct effect on the near-edge region which is reproduced by theoretical simulations performed in the Monte-Carlo approach.