Identifying Reaction Species by Evolutionary Fitting and Kinetic Analysis: An Example of CO₂ Hydrogenation in DRIFTS

Abstract

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations of molecules at the surface of catalysts exhibit a strong overlap of the adsorption peaks. Therefore, the investigation of the CO 2 hydrogenation on a highly active catalyst surface requires a deconvolution of the adsorption spectra to clearly assign the signal to the chemical species. We developed an autonomous and efficient bi-level evolutionary Gaussian fitting (BEGF) procedure with a genetic algorithm at the upper level and a multipeak Gaussian fitting algorithm at the lower level to analyze self-consistently the set of spectra of an entire experiment. We show two examples of the application of BEGF procedure by analyzing the DRIFTS spectral sets of ex situ HCOO − * and CO 2 hydrogenation on Ru/Al 2 O 3. The fitting procedure deconvoluted the overlapped peaks and identified the bond vibrations of carbon monoxide, formate, bicarbonate, and carbonate through the developing trends of the peak intensities along the reaction. These revealed the progression of those species over the reaction timeline.

Direct CO2 Capture and Reduction to High‐End Chemicals with Tetraalkylammonium Borohydrides

“…We deconvoluted the peak of this region and showed the development of each peak along with reaction time (Figure 5). [58] For both samples, the peaks at 1712 and 1664 cm −1 grew as CO 2 flowed on to the sample surface. After about 10 minutes, the peaks at higher frequencies, represented by the peak at 1830 cm −1 , rose and kept increasing, indicating more CO 2 molecules were transformed to formate.…”

Solvent‐ and Catalyst‐Free Carbon Dioxide Capture and Reduction to Formate with Borohydride Ionic Liquid

“…New peaks between =1750 and 1550 cm −1 grow with time after CO 2 flowed in. We deconvoluted and integrated the peaks, and the development of each peak as a function of reaction time is shown in Figure . The intensity of the B−H peak decreased by 64 % and approached equilibrium after 200 min, consistent with the MSB data.…”

Infrared Thermography as an Operando Tool for the Analysis of Catalytic Processes: How to Use It?

“…In this phase, all the O2 fed in the form of CO2 is converted into oxygenated surface species and no H2O product is formed, as visible in figure 11b (first 10-20 seconds of the reaction). When the local equilibrium between reduced and oxidized surface species is reached (details about the nature of these species can be found in our previous studies [40,41]), the reaction reaches the steady state conditions, with the characteristics described above. These examples shows how the effective coupling of IR thermography and fast concentration measurements (e.g.…”