In situ X-ray emission and high-resolution X-ray absorption spectroscopy applied to Ni-based bimetallic dry methane reforming catalysts

Abstract

The effect of cobalt on the catalytic activity of a NiCoO dry methane reforming catalyst was investigated by in situ XES and HERFD XAS. Co is shown to hamper the reduction of the Ni in the NiCoO catalyst by modulation of its electronic structure.

Mechanistic and Electronic Insights into a Working NiAu Single-Atom Alloy Ethanol Dehydrogenation Catalyst

“…However, the XPS approach becomes impossible for supported dilute alloy catalysts in which the dopant concentration is <1% as XPS is not a trace element technique (∼100 ppm in the case of NiAu/SiO 2 SAA), a concentration regime at which HERFD XANES provides analyzable information. Similar evidence of the electronic structure modulation of Ni by the presence of another metal has been demonstrated by DeBeer and co-workers in Ni 3 Co 1 alloys, as evidenced via HERFD XANES analysis, as well as by the Bao group on Ni 1 Pt 4 alloys based on conventional XANES measurements; however in both cases considerably higher concentrations of Ni were present in the samples. , …”

“…Similar evidence of the electronic structure modulation of Ni by the presence of another metal has been demonstrated by DeBeer and co-workers in Ni 3 Co 1 alloys, as evidenced via HERFD XANES analysis, as well as by the Bao group on Ni 1 Pt 4 alloys based on conventional XANES measurements; however in both cases considerably higher concentrations of Ni were present in the samples. 64,65 While little experimental data exist for charge transfer in SAAs, the electronic structure of Ni atoms in NiAu SAAs has been examined theoretically. 66 Specifically, the d states of Ni atoms in a Au(111) host were computed by Thirumalai and Kitchin, and their results revealed a very narrow electronic state near the Fermi level indicative of a lack of hybridization of the Ni d states with the host Au.…”

Effects of alloying for steam or dry reforming of methane: a review of recent studies

“…117 Many reports have described the existence of an optimal Co/Ni ratio, but the value varies depending on the catalyst. In addition, in situ XPS, 116 and in situ scanning transmission X-ray microscopy (STXM) 118,119 studies have been conducted recently.…”

“…Askari et al 118,119 investigated Ni-Co alloy catalysts using the technique of in situ STXM and showed a different result of in situ XPS study by Wu et al 116 Askari et al 118 first prepared NiCoO x /γ-Al 2 O 3 catalyst by the modified reverse micellar method, of which compositions are determined by EDX as 56.4 atom% of O, 1.1 atom% of Co, 9.2 atom% of Ni, and 33.3 atom% of Al. Later, STXM studies of NiCoO x /γ-Al 2 O 3 catalyst were conducted under Ar, 5%H 2 /Ar, and DRM atmosphere.…”

Synchrotron-radiation spectroscopic identification towards diverse local environments of single-atom catalysts

“…Besides XANES and EXAFS, so XAS is also efficient in the detection of chemical states, orbital hybridization and atom-specic local environments of SACs. [63][64][65] It is also demonstrated that establishing traditional characterization methods based on synchrotron-radiation light can improve their data quality and reliability to a large extent. For instance, synchrotron radiation XPS, one of the most important surface-sensitive characterization methods, can obtain the surface information of catalysts with high energy resolution.…”