Raman and infrared linewidths of CO in Ar

Tailoring Interfaces for Enhanced Methanol Production from Photoelectrochemical CO2 Reduction

Efficient and stable photoelectrochemical reduction of CO2 into highly reduced liquid fuels remains a formidable challenge, which requires an innovative semiconductor/catalyst interface to tackle. In this study, we introduce a strategy involving the fabrication of a silicon micropillar array structure coated with a superhydrophobic fluorinated carbon layer for the photoelectrochemical conversion of CO2 into methanol. The pillars increase the electrode surface area, improve catalyst loading and adhesion without compromising light absorption, and help confine gaseous intermediates near the catalyst surface. The superhydrophobic coating passivates parasitic side reactions and further enhances local accumulation of reaction intermediates. Upon one-electron reduction of the molecular catalyst, the semiconductor-catalyst interface changes from adaptive to buried junctions, providing a sufficient thermodynamic driving force for CO2 reduction. These structures together create a unique microenvironment for effective reduction of CO2 to methanol, leading to a remarkable Faradaic efficiency reaching 20% together with a partial current density of 3.4 mA cm-2, surpassing the previous record based on planar silicon photoelectrodes by a notable factor of 17. This work demonstrates a new pathway for enhancing photoelectrocatalytic CO2 reduction through meticulous interface and microenvironment tailoring and sets a benchmark for both Faradaic efficiency and current density in solar liquid fuel production.

Ab initio investigation of the CO-N2 quantum scattering: The collisional perturbation of the pure rotational R(0) line in CO

We report fully quantum calculations of the collisional perturbation of a molecular line for a system that is relevant for Earth's atmosphere. We consider the N₂-perturbed pure rotational R(0) line in CO. The results agree well with the available experimental data. This work constitutes a significant step toward populating the spectroscopic databases with ab initio collisional line-shape parameters for atmosphere-relevant systems. The calculations were performed using three different recently reported potential energy surfaces (PESs). We conclude that all three PESs lead to practically the same values of the pressure broadening coefficients.

Gas phase methanol synthesis with Raman spectroscopy for gas composition monitoring

Applicability of Raman spectroscopy for time-resolved gas composition monitoring during direct methanol synthesis via carbon dioxide hydrogenation was investigated. A series of methanol synthesis experiments with varied reactor conditions was conducted and the reactor outlet stream was analyzed with in-line gas Raman spectroscopy. Concentrations of H₂, CO₂ and CO were determined directly from the acquired spectral data. For evaluation of methanol and water content a data reconciliation algorithm was developed. The algorithm involves estimation of the occurring chemical reactions' extents by iterative minimization of the difference between concentration values acquired from the experimental data and concentration values computed based on the mass conservation principle. The obtained experimental concentrations were compared and validated against the results of the reactor mathematical modeling, which is based upon a well-established kinetic interpretation of the process. The findings indicate good repeatability and accuracy of the developed gas analysis system, which together with the advantageous temporal resolution of the method, make Raman spectroscopy a promising technique for fast response monitoring of the process.

Applicability of Raman spectroscopy for time-resolved gas composition monitoring during direct methanol synthesis via carbon dioxide hydrogenation is investigated.

Intermolecular interaction potentials for the Ar–C2H2, Kr–C2H2, and Xe–C2H2 weakly bound complexes: Information from molecular beam scattering, pressure broadening coefficients, and rovibrational spectroscopy

Integral cross sections and pressure broadening coefficients have been measured for the acetylene-krypton complex, by molecular beam scattering and by high resolution IR spectroscopy, respectively. A new potential energy surface (PES) is proposed to describe structure and dynamical properties of this prototypical weakly bound complex. The PES has been parametrized exploiting a novel atom-bond pairwise additive scheme and has been fitted to the experimental data. A similar PES has been obtained for the acetylene-xenon system by a proper scaling of the interaction parameters of the krypton case, based on empirical considerations. These PESs together with that recently proposed by the same authors [J. Phys. Chem. 109, 8471 (2005)] for the acetylene-argon case have been employed for close coupling calculations of the pressure broadening cross sections and for a characterization of the rovibrational structure of the complexes.

Determination of Carbon Monoxide Concentration and Total Pressure in Gas Cavities in the Silica Glass Body of Light Bulbs by FT-IR Spectrometry

Fourier transform infrared (FT-IR) spectroscopy has been adapted to control the quality of light bulbs made from silica glass. Such light bulbs contain a molybdenum accessory which, if contaminated with carbon, during the melting procedure of bulb fabrication, can cause the production of carbon monoxide. This CO can be trapped in small gas cavities in the silica glass body of the bulb. A method has been developed for the detection of CO and the total pressure within these gas cavities by traditional FT-IR spectrometry using a spectral resolution of 0.5 cm(-1). The concentration of CO was determined by using a classical least-squares (CLS) method, and the accuracy of concentration determination is reported for the case with sample and reference spectra recorded at different pressures. The total pressure in the cavities was established by two different methods: either by CLS fitting of reference spectra to sample spectra or fitting a Voigt line shape function to the spectral lines within the CO fundamental stretching band. In the latter method, the width of the lines was determined and pressure-broadening coefficients are given and compared with high-resolution data from the literature. According to the measurements, 0.55-0.80 atm total pressure and 0.8-4.0% (v/v) CO was determined in the gas cavities. This method can also be applied to determine the total pressure in similar enclosed spaces in which an appropriate indicator gas component exists.

Collision Cross Sections, Pressure-Broadening Coefficients and Second Virial Coefficients for the Acetylene-Argon Complex: Experiments and Calculations on a New Potential Energy Surface

Integral cross sections and pressure-broadening coefficients have been measured by molecular beam scattering and by high-resolution infrared spectroscopy, respectively, for the acetylene-argon system. A new potential energy surface (PES) is proposed to describe structure and dynamical properties of this prototypical weakly bound complex. The PES has been parametrized exploiting a novel atom-bond pairwise additive scheme and has been fitted to the experimental data. Calculations of the scattering cross sections (both differential and integral), pressure-broadening, and second virial coefficients have been performed using both the present and also the most recent ab initio PES available in the literature. Analysis of the new experimental data indicates that the anisotropy of the interaction in the well region should be larger than that obtained in ab initio calculations. This is also in line with previous spectroscopic results.