Quantitative analysis of infrared spectra of adsorbed species using transmission and diffuse reflectance modes

Heat of adsorption of CO on EUROPT-1 using the AEIR method: Effect of analysis parameters, water and sample mode

“…The DRIFT spectra (reported in pseudo-absorbance mode: log (1/R), where R is the sample reflectance) were recorded at a resolution of 4 cm −1 and 32 scans were averaged. The pseudo-absorbance gives a better linear representation of the band intensity against surface coverage than that given by the Kubelka-Munk function for strongly absorbing media such as those based on metals supported on oxides [28,29]. The preparation of the catalyst sample for the quantitative exploitation of the IR spectra in diffuse reflectance mode was similar to previous studies [29,30].…”

“…For adsorbed CO species with low heats of adsorption leading to a decrease in their IR bands for T a < ≈ 500 K, the thermal gradient is minimized and it has no significant impact on the measurement (i.e. on the E L (1) in the present study see also [29] [48]).…”

Spectrum baseline artefacts and correction of gas-phase species signal during diffuse reflectance FT-IR analyses of catalysts at variable temperatures

“…In situ DRIFTS spectra recorded over 14% Co/alumina at 220°C (a) in the presence of 25 30 % CO + 60 % H 2 + 10 % Ar at steady-state. The spectrum (b), (c) (d) and (e) are equal to 26 (a) to which a gas-phase spectrum of CO recorded over SiC at 50°C was subtracted to 27 different proportions, i.e. 0.5, 0.7, 0.9 and 1.1-fold respectively.…”

“…12 DRIFTS exhibits a higher sensitivity with respect to surface species and strongly 13 absorbing samples such as carbon-based materials can be studied [22]. It was demonstrated 14 that DRIFTS could be used for quantitative analysis to determine the surface concentration of 15 adsorbates [5,23,24,25] and the heat of adsorption of CO on oxides and supported metals [26]. 16 In particular, DRIFTS analyses were able to show that the heat of CO adsorption on a Pt-Sn 17 alloy was about half the value measured on plain Pt, and that Pt-Sn segregation took place 18 reversibly in the presence of CO when the temperature was lower than 175°C [27].…”

“…A c c e p t e d M a n u s c r i p t 3/3 DRIFTS utilization is not exempt of difficulties, particularly regarding the quantitative 1 analyses of the IR bands of adsorbed species [26,35,36] and the present study focuses on 2 different artifacts may arise during the handling of the DRIFT spectra. 3 The correction of gas-phase signal is particularly important in the case of CO-based 4 analyses since the signals of gas-phase CO and adsorbed CO may overlap extensively.…”