Operando QEXAFS studies of Ni₂P during thiophene hydrodesulfurization: direct observation of Ni-S bond formation under reaction conditions.
Structural changes in Ni(2)P/MCM-41 were followed by quick extended X-ray absorption fine structure (QEXAFS) and were directly related to changes in X-ray absorption near-edge structure (XANES) which had been used earlier for the study of the active catalyst phase. An equation is proposed to correct the transient QEXAFS spectra up to second-order in time to remove spectral distortions induced by structural changes occurring during measurements. A good correlation between the corrected QEXAFS and the XANES spectral changes was found, giving support to the conclusions derived from the XANES in the previous work, namely that the formation of a Ni-S bond in a surface NiPS phase is involved in the active site for the hydrodesulfurization reaction.