The challenges of characterising nanoparticulate catalysts: general discussion

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

“…367 In this context, INS technique coupled with hydrogen adsorption measurements is a powerful tool to locate Pt NP on activated carbon and to observe Pt hydride formation. 368,369 EXAFS experiments have been also used to characterize in situ the interaction between Pt NP on CNF, in terms of Pt-C bonds. 370 The presence of oxygen-surface groups on CNF leads to the stabilization of Pt NP.…”

“…In the case of bimetallic Pt n Fe (55– n ) ( n = 0, 11, 13, 18, 28, 37, 42, 44, 55) NP on graphene SV, it was found by DFT that the NP prefer to be adsorbed on the SV through the Fe atoms (Pt and Fe atoms are both on the surface), because of the stronger interaction between Fe atoms and SV . In this context, the INS technique coupled with hydrogen adsorption measurements is a powerful tool to locate Pt NP on AC and to observe Pt hydride formation. , EXAFS experiments have also been used to characterize in situ the interaction between Pt NP on CNF, in terms of Pt–C bonds . The presence of oxygen-surface groups on CNF leads to the stabilization of Pt NP.…”

Gas phasevs.liquid phase: monitoring H2and CO adsorption phenomena on Pt/Al2O3by IR spectroscopy

“…5,6 Understanding the nature and the behaviour of the platinum hydride (Pt-H) species under reaction conditions is crucial to design more efficient and profitable catalysts. However, characterizing the phenomena occurring at the surface of supported metal nanoparticles is one of the main challenges in surface science, due to the combination of many factors, among which are the intrinsic complexity of metal nanoparticles [7][8][9][10][11][12][13] and their dynamic behaviour in the presence of adsorbates. [14][15][16][17][18][19][20][21][22][23][24] In this context, the H 2 @Pt system was extensively investigated both theoretically 15,16,21,[24][25][26][27][28] and experimentally, especially by means of X-ray absorption spectroscopy (XAS), 13,14,17,18,22,25,[29][30][31][32][33][34][35][36] IR spectroscopy [37][38][39]…”

Dynamics of Reactive Species and Reactant-Induced Reconstruction of Pt Clusters in Pt/Al2O3Catalysts

“…Part of the difficulty is associated with the intrinsic complexity of nanosized noble metal clusters. − In the last decades a large amount of experimental evidence demonstrated that the Pt clusters undergo electronic and morphological reconstruction as a function of the support, of the adsorbate, and of the reaction temperature. ,− Pt L 3 -edge XAS spectroscopy (in both XANES and EXAFS regions) has been one of the main techniques employed to investigate the structural and electronic changes experienced by nanometric Pt particles supported on different materials in the presence of hydrogen. As far as the XANES region is concerned, it has been observed that H 2 adsorption on small Pt particles causes dramatic changes in the spectra: the “white line” intensity decreases and the spectra broaden to higher energy as hydrogen is added. ,− ,− There have been many efforts to interpret these effects, which are due to both electronic and geometric phenomena. ,− Most of the analyses are based on subtracting the Pt L 3 -edge spectrum of the catalyst in the absence of adsorbed hydrogen (μ­(Pt)) from those in the presence of adsorbed hydrogen (μ­(Pt–H)), also known as the ΔXANES approach .…”