RETRACTED ARTICLE: Revisiting the Evolution of IR Spectra of CO Adsorbed on Au Nanoparticles Supported on Non-reducible Supports
Authors: Atwi, Ranin
Elgayyar, Taha
Cadete Santos Aires, Francisco J.
Tuel, Alain
Meunier, Frederic C.
Journal: Topics in Catalysis (2020)
Discipline: CHEMISTRY
Keywords: Gold surfaces; nanoparticles; IR spectroscopy; carbon monoxide; evolution

Abstract: Gold surfaces and nanoparticles have commonly been investigated by IR spectroscopy using carbon monoxide as a molecular probe. An evolution of the IR spectra with time under CO was reported in&nbsp;some cases and tentatively assigned to geometrical effects (e.g. surface reconstruction or particle restructuring) or electronic effects, e.g. gold becoming negatively charged following support reduction. We report here an investigation of the evolution of the IR spectrum of CO adsorbed at 50&nbsp;°C in the case of Au nanoparticles supported on non-reducible silica and alumina supports. The evolution of the carbonyl IR band signal, proposed to arise mostly from Au particle restructuring, was clearly observed. In addition, the formation of hydrogenocarbonates species on the alumina reemphasized that Au nanoparticles are somewhat active for CO dissociation via Boudouard reaction near room temperature, leading to some deposition of carbon. Water could not prevent restructuring, while O2 prevented irreversibly the reconstruction, which could even be reversed when O2 was introduced on an already restructured sample. It is hypothesized that the role of O2 would be to remove the deposited elemental carbon that otherwise stabilize reconstructed Au. These results emphasize the complexity of the parameters affecting the restructuration of Au surfaces induced by CO and the difficulty in interpreting IR spectra of CO adsorption on Au-based materials.

Retracted: Yes

PubPeer comments:
 We are the authors of this paper [1] entitled u201cRevisiting the Evolution of IR Spectra of CO Adsorbed on Au Nanoparticles Supported on Non-reducible Supportsu201d, in which we had related the temporal evolution of the IR bands of CO adsorbed on Au to a hypothetical reconstruction process. Work from Yao et al. [2] recently pointed out that a similar effect could be induced by the presence of nickel through contamination by Ni(CO)4. We have since re-examined our data and noted that up to 5 ppm of Ni(CO)4 were unexpectedly observed in the effluent gases of the diffuse reflectance FT-IR (DRIFTS) cell that had not been noticed at the time. No Ni(CO)4 was yet detected in the high purity 5% CO He from Lu2019Air Liquide, which had been further purified using a liquid N2 trap. Ni(CO)4 could not be detected either when CO had been cofed with O2 or if the cell reactor had not previously been raised to 300u00b0C under H2. We conclude that part of the cell (from Harrick) had been corroded, probably by NOx used during the same period, and reacted with CO to form Ni(CO)4 in situ, only when the nickel present had been reduced to the metallic state. We have now tried to reproduce the experiment reported in [1] over the same materials using a new Harrick cell and we can no longer observe the major Au-CO band shift from ca. 2106-2110 cm-1 down to 2070-2060 cm-1 with concomitant several-fold intensity increase that occurred in less than 10 min (see figure 3.A and 6.A in [1]). In contrast, the band position and intensity remain constant over 60 min (Figure 1). ![file] Figure 1: (Top) In situ DRIFTS spectra at 50u00b0C after reduction at 300u00b0C in H2 under 1% or 5% CO He observed over (A) 2.1% Au alumina and (B) 1% Au silica. (Bottom) Corresponding DRIFTS spectra during desorption in He. We therefore conclude that the spectral evolutions reported in our earlier report were likely the result of Ni(CO)4 contamination and the deposition of Ni over the Au nanoparticles, leading to Ni-CO species being formed replacing Au sites and not to any restructuring as we had regrettably indicated. It is interesting to note that a sample of Au encapsulated in a silicalite-1 zeolite that had been exposed to Ni(CO)4 did not show this band shift, indicating that Ni(CO)4 could not enter the pores of silicalite-1 at 50u00b0C. We hope that our unfortunate experience will raise more awareness of the potential pitfalls associated with using CO at low temperatures on corroded steel cells. We have asked the journal to retract our paper. Frederic C. Meunier, Ranin Atwi, Taha Elgayyar, Francisco J. Cadete Santos Aires and Alain Tuel. Univ Lyon, Universitu00e9 Claude Bernard Lyon1, CNRS, Institut de Recherches sur la Catalyse et lu2019Environnement de Lyon, IRCELYON, 2, Av. Albert Einstein F-69626 Villeurbanne References: 1. Atwi R, Elgayyar T, Cadete Santos Aires FJ, Tuel A. Meunier, F (2020) Top. Catal. 63 :1596u22121605. 2. Yao Y, Chen L, Mao X, Yang Y, Chen J, Zhou L (2021) J. Phys. Chem. C 125:8606u22128619 ,