In Situ DRIFTS and NAP-XPS Exploration of the Complexity of CO₂ Hydrogenation over Size-Controlled Pt Nanoparticles Supported on Mesoporous NiO

Abstract

Infrared Fourier Transform Spectroscopy (DRIFTS). In the case of pure NiO, we found that the surface of the support was mainly covered by elemental Ni under reaction condition, where the Ni/NiO x system is responsible for the high activity of Pt-free catalyst. In the case of Pt/NiO, Pt improves the reduction of NiO x towards metallic Ni. In the case of the 1 % Pt/NiO catalysts, the presence of limited amount of Pt resulted in an optimal quantity of oxidized Pt fraction at 673 K showing the presence of a Pt/PtO x /Ni/NiO x mixed phase where the different interfaces may be responsible for the high activity and selectivity towards methane. In the case of pure NiO under reaction condition, small amounts of formaldehyde as well as hydrogen perturbed CO [H n CO (n=1,2)] were detected. However, in the case of 1 % Pt/NiO catalysts, besides the absence of formaldehyde a significant amount of H n CO (n=2-3) was present on the surface responsible for the high activity and methane selectivity.

Development and Application of Carbon‐Layer‐Stabilized, Nitrogen‐Doped, Bamboo‐Like Carbon Nanotube Catalysts in CO2 Hydrogenation

“…On Pd‐supported Al 2 O 3 catalysts, methane formation was dominant, whereas using SiO 2 , MgO and TiO 2 supports CO was the major product . The ratio of Ni:NiO also strongly determines the selectivity of the CO 2 hydrogenation: higher metallic content favors methane formation . All of these findings emphasize the importance of the nature of the metal/support interface.…”

“…[37] The ratio of Ni:NiO also strongly determines the selectivity of the CO 2 hydrogenation:h igher metallic content favors methane formation. [29] All of these findings emphasize the importance of the nature of the metal/support interface. The absence of an oxide-like interaction between the metal and BCNT could be the reason for high CO selectivity in the present study.T he BCNT ensures as pherical, site-specific arrangement for the metal where the CO 2 reductive activation may occur.I n the case of Ni/BCNT there is ac hance to build up af avorable Ni/NiO composition at am oderatet emperature where the methane formation is dominant.…”

Synergetic of Pt Nanoparticles and H-ZSM-5 Zeolites for Efficient CO2 Activation: Role of Interfacial Sites in High Activity

“…The Pt NP dispersion on the surface of the H-ZSM-5 supports may depend on the acidic strength of the support: the more acidic is the surface, the less sintering during the reaction maybe expected. However, earlier studies showed that Pt nanoparticles with >5 nm sizes are not showing any sintering under similar reaction conditions (Sápi et al, 2018). It is worth mentioning that the lack of the Brønsted acidic sites over the zeolite supports, the Pt NPs are not stable and consequently might be leading to the formation of their agglomeration over the support.…”

“…These bands can be attributed to the formation of formate ion (HCOO − ) from the CO 2 + H 2 reaction mixture, and these are assigned to ν a (OCO) and ν s (OCO) vibrations, respectively (Liao et al, 2001;Raskó et al, 2004). When the reaction temperature is increased to 573 K, a new weak peak developed at 1,737 cm −1 which can be tentatively assigned to aldehyde like CO stretch (Novák et al, 2002;Sápi et al, 2018). These bands were present up to 873 K, from 673 K peaks for gas phase CO (2,115 and 2,167 cm −1 ) and methane (3,013 cm −1 ) showed up (not shown here).…”

“…Typically, ZSM-5 are used as sorbents and catalyst due to their unique channel structure, thermal stability, acidity, and shape-selective property (Falamaki et al, 1997;Kumar et al, 2002;Cheng et al, 2005;Ismail et al, 2006). Furthermore, the boosting effect of the size-controlled Pt nanoparticles (NPs) on the hydrogenation reaction of CO 2 was extensively studied and was attributed to the active cooperation of the metallic Pt and oxide support (Sápi et al, 2018). In this work, our purpose is to prove that the anchoring of Pt NPs on different ZSM-5 zeolite supports is a favorable heterogeneous hybrid catalyst for the hydrogenation of CO 2 into valuable products.…”