The review is a summary and analysis of the data characterizing CO adsorption on surface cationic sites of oxides including supported materials and microporous and mesoporous materials. The contributions of various types of CO bonding to the IR frequency shifts of carbon-bonded molecules are analyzed, namely, the increase of the CO stretching frequency in cases of electrostatic and σ bonding and the decrease of the frequency with π bonding. Polycarbonyls, bridging CO, oxygen-bonded CO, and tilted CO are also considered. The main part of the review is a collection of the experimental results characterizing carbonyls of individual metal ions. The spectral behavior of CO bonded to metal atoms is also assessed in the cases when the metal ions are easily reduced to metal (Cu, Ag, Au, Pd, or Pt) or cationic carbonyls are produced after CO adsorption on supported metals (Ru, Rh, Ir, and Os). The interaction of CO with surface OH groups is also considered. It is demonstrated that IR spectroscopy of adsorbed CO is an efficient methodology to characterize cationic surface sites in terms of their nature, oxidation states, coordination environment and coordinative unsaturation, and location at faces, edges or corners of microcrystallites. When applied to materials with surface hydroxyl groups CO undergoes hydrogen bonding and information can be collected on the proton acid strength.

Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule

Ni/CeO2 catalysts with high CO2 methanation activity and high CH4 selectivity at low temperatures

CO2 methanation is a well-known reaction that is of interest as a capture and storage (CCS) process and as a renewable energy storage system based on a power-to-gas conversion process by substitute or synthetic natural gas (SNG) production. Integrating water electrolysis and CO2 methanation is a highly effective way to store energy produced by renewables sources. The conversion of electricity into methane takes place via two steps: hydrogen is produced by electrolysis and converted to methane by CO2 methanation. The effectiveness and efficiency of power-to-gas plants strongly depend on the CO2 methanation process. For this reason, research on CO2 methanation has intensified over the last 10 years. The rise of active, selective, and stable catalysts is the core of the CO2 methanation process. Novel, heterogeneous catalysts have been tested and tuned such that the CO2 methanation process increases their productivity. The present work aims to give a critical overview of CO2 methanation catalyst production and research carried out in the last 50 years. The fundamentals of reaction mechanism, catalyst deactivation, and catalyst promoters, as well as a discussion of current and future developments in CO2 methanation, are also included.

Supported Catalysts for CO2 Methanation: A Review

CO2 methanation on Ru-doped ceria

Transient measurement techniques are applied for the kinetic investigation of the reaction mechanism of the carbon dioxide methanation, using diffuse reflectance infrared spectroscopy and mass spectrometry. The coupled information of the surface intermediates and the gas phase components time evolution leads to accurate identification of spectator species on the surface. Reaction intermediates, carbon monoxide and formates have been identified. The former is a key intermediate, and its hydrogenation leads to methane formation. The latter is fixed on the support, in equilibrium with a active formate species on the interface metal-support. A reaction mechanism is proposed including the formation step of the formates through a carbonate species.

In-situ surface and gas phase analysis for kinetic studies under transient conditions The catalytic hydrogenation of CO2

FTIR spectroscopic study of the interaction of CO2 and CO2 + H2 over partially oxidized Ru/TiO2 catalyst

The transient species formed over Ru$z.sbnd;RuOx/TiO2 catalyst in the CO and CO + H2 interaction: FTIR spectroscopic study

Microcalorimetric study of the interaction of CO, O2, and CO + O2 with Pt/SnO2 and SO2 catalysts

FTIR spectra of a Ru-RuOx/TiO2 catalyst obtained on co-adsorption of CO, CO2 and H2 in the temperature range of 300–500 K were found to be the sum total of corresponding spectra observed during methanation of individual oxides. The two oxides compete for metal sites and at each temperature they reacted simultaneously to form distinct transient Ru(CO)n type species even though the nature, the stability and the reactivity of these species were different in the two cases. The monocarbonyl species formed during adsorption/reaction of CO alone or of CO + H2 were bonded more strongly than those formed during CO2 + H2 reaction.

FTIR studies on the CO, CO 2 and H 2 co-adsorption over Ru-RuO x /TiO 2 catalyst

Microcalorimetric Study of the Adsorption and Reaction of CO, O2, CO + O2, and CO2 on NaX Zeolite, Pt/NaX, and Platinum Metal: Effect of Oxidizing and Reducing Pretreatment

R.M. Iyer

Papers

FTIR spectroscopic study of the interaction of CO2 and CO2 + H2 over partially oxidized Ru/TiO2 catalyst

The transient species formed over Ru$z.sbnd;RuOx/TiO2 catalyst in the CO and CO + H2 interaction: FTIR spectroscopic study

Microcalorimetric study of the interaction of CO, O2, and CO + O2 with Pt/SnO2 and SO2 catalysts

FTIR studies on the CO, CO 2 and H 2 co-adsorption over Ru-RuO x /TiO 2 catalyst

Microcalorimetric Study of the Adsorption and Reaction of CO, O2, CO + O2, and CO2 on NaX Zeolite, Pt/NaX, and Platinum Metal: Effect of Oxidizing and Reducing Pretreatment