Diffuse Reflectance Infrared Fourier Transform Research Articles

Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO2 and methanol over ceria catalysts

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes. Herein, a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO2 and methanol, and the structure-performance relationship was investigated in detail. Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies indicated that the adsorption rate of methanol is slower than that of CO2 and the methanol activation state largely influences the formation of key intermediate. Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO2, the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation. Moreover, with the use of 2-cyanopyridine as a dehydration reagent, the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

Cation rearrangement at tetrahedral sites in the Cu/ZnAl2O4 spinel enhancing CO2 hydrogenation to methanol

Cu/ZnAl2O4 spinel is a promising catalyst for CO2-to-methanol due to its dual-site H2 activation. However, controlling surface properties and metal-support interactions (MSI) through the coordination environment of spinel cations remains underexplored. Herein, the occupancy of Zn2+ and Al3+ cations in Cu/ZnAl2O4 spinel is fine-tuned by manipulating the calcination atmosphere. More disordered structures (AlO4 and ZnO6) observed on the CZA-Ar catalyst benefit the creation of oxygen vacancies and surface hydroxyl groups, which facilitate the formation of highly dispersed small-sized Cu species. This enhances MSI and hydrogen spillover effects, thereby boosting CO2 conversion and the space-time yield (STY) of methanol. High-pressure in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results reveal that the crucial formate intermediates form at tetrahedral sites in ZnAl2O4 spinel, with more Al-HCOO- species observed on the CZA-Ar catalyst due to the formation of AlO4. This work advances the understanding of spinel catalysts in CO2 hydrogenation to methanol.

A MOF@MOF S-scheme Heterojunction with Lewis Acid-Base Sites Synergistically Boosts Cocatalyst-Free CO2 Cycloaddition.

The photocatalytic cycloaddition reaction between CO2 and epoxide is one of the most promising green routes for CO2 utilization, for which high performance photocatalysts are intensely desired. Herein, we have constructed an S-scheme heterojunction of MIL-125@ZIF-67 modified by amino groups, which achieves a cyclic carbonate yield of as high as 99 % without employing any co-catalyst, outperforming the previously reported photocatalysts. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in-situ electron paramagnetic resonance (EPR) spectroscopy reveal the important role of photogenerated electron migration from Lewis acid (Co) sites to the O atom of epoxide in triggering its ring-opening (the rate-determining step of CO2 cycloaddition reaction) under the assistance of photogenerated hole. Synergistically and concurrently, the Lewis base (amino groups) sites activate CO2 to CO2*, facilitating the following CO2 cycloaddition. Such a synergistic effect provides a most favorable approach to design efficient heterogeneous photocatalysts with dual/multiple-active sites for CO2 cycloaddition reaction.

The enhanced SO2 resistance of Fe-Ti catalyst by W/SO42− co-modification for NH3-SCR: A combined experimental and DFT study

It remains a great challenge to improve the low-temperature SO2 resistance of catalysts applied for selective catalytic reduction of NOx with NH3 (NH3-SCR). This work develops an outstanding SO2-tolerant Fe-Ti (FT) catalyst by W/SO42− co-modification via a sol–gel method using Fe(NO3)3·9H2O, tetrabutyl titanate, ammonium tungstate and thiourea as raw materials. The physicochemical characterizations, in-situ diffuse reflectance infrared Fourier transform (DRIFT) measurements and density functional theory (DFT) calculations were combined to reveal the underlying mechanisms. Although W doping can effectively enhance the surface acidity, NH3 adsorption on Lewis acid sites can still be restrained by competitive adsorption of SO2, whereas SO42− modification can enhance the adsorption stability of NH3 without being affected by SO2. Simultaneously, the NO adsorption ability on Fe sites can be significantly enhanced by W/SO42− co-modification. Furthermore, the W doping or SO42− modification can induce conversion of Fe3+ to Fe2+ to affect the redox property of Fe species. A proper amount of Fe2+ suppressed the oxidizability of FT catalyst to inhibit NH3 overoxidation to enhance N2 selectivity, and created more oxygen vacancies to generate larger amount of chemisorbed oxygen to facilitate NH3 dehydrogenation and NO oxidation. More importantly, the inhibition effect of SO2 adsorption on Fe sites was strengthened by W/SO42− co-modification. Consequently, the W/SO42− co-modified FT catalyst exhibited high activity with >90 % of NO conversion and >95 % of N2 selectivity within a broad window of 275–450 °C and possessed superior SO2 + H2O tolerance at 275 °C.

Highly active ternary Ir/In2O3-ZrO2 catalyst for CO2 hydrogenation towards methanol: The role of zirconia

Indium oxide supported iridium catalyst has been verified to be highly active and selective for CO2 hydrogenation to methanol. In this work, zirconia is introduced into the Ir/In2O3 system as a novel Ir/In2O3-ZrO2 ternary catalyst. The solid solution generated between ZrO2 and In2O3 exhibits a strong electronic metal-support interaction with iridium, rendering the supported iridium species highly dispersed in a form of clusters. Thereout, an active interface between iridium and the solid-solution carrier is thus generated, on which electron transport is more feasible with a stronger CO2 adsorption than that of on the Ir−In2O3 interfacial site. Moreover, compared to Ir/In2O3, this ternary catalyst exhibits better catalytic activity as well as the stability. Density functional theory (DFT) simulations, combined with the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, further demonstrate the CO-hydrogenation pathway is the most favored for methanol synthesis, providing a rationale for the superior methanol selectivity of the Ir/In2O3-ZrO2 catalyst during CO2 hydrogenation.

Ta4SBr11: A Cluster Mott Insulator with a Corrugated, Van der Waals Layered Structure.

The compound Ta4SBr11 was prepared by a comproportionation reaction of tantalum bromide with tantalum and elemental sulfur. The crystal structure, as refined by single-crystal X-ray diffraction, is composed of clusters with Ta4S cores, arranged in corrugated van der Waals layers. Individual layers appear to be displaced relative to each other along one direction. Successful crystal growth in a melt of CsBr yielded black platelets of Ta4SBr11, which were used to investigate the electrical properties of the compound. The electronic structure was studied by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and by density functional theory (DFT) band structure calculations, revealing this material to be a small-gap semiconductor. DFT results, in combination with magnetic susceptibility measurements, suggest that metallicity originating from the one unpaired Ta d electron per cluster is most likely suppressed by electronic correlations, forming a cluster Mott insulator.

Mixed bio-based surfactant-templated mesoporous silica for supporting palladium catalyst

The study aimed on the synthesis of bio-based surfactant-templated mesoporous silica for supporting palladium catalyst using mixed bio-based templating agents namely cashew nut shell liquid (CNSL) and castor oil for pore direction purposes. The materials prepared through co-condensation of 3-aminopropyltriethoxysilane (APTS) and tetraethyl orthosilicate (TEOS) in a 1:4 M ratio using 1:1, 4:1 and 9:1 ratio of CNSL and castor oil. The resulting porous materials were utilized to support the palladium(II) chloride catalyst, resulting in a heterogeneous catalyst-a better and more environmentally friendly catalyst than a homogeneous one. Different instruments were used to characterize the prepared materials such as nitrogen porosimeter, Powder X-ray Diffraction, Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Inductively coupled plasma optical emission spectroscopy. Physisorption studies of the prepared materials indicated that the largest pore diameter of 43.84 nm could be obtained by using a 1:1 M ratio of CNSL and castor oil. On the other hand, the largest surface area of 209 m2/g was obtained from a 9:1 whereas the largest pore volume was 1.55 cm3/g from a 4:1. Diffuse Reflectance Infrared Fourier Transform Spectroscopy analysis confirmed the presence of N-H group, the bending vibration bands at around 1640 and 1543 cm−1 indicating that the reaction of organoaminesilanes and tetraethyl orthosilicate had occurred. The palladium content of the supported catalyst was determined by ICP-OES which confirmed the attachment of palladium to the synthesized materials. The highest palladium loading was obtained from the adsorbent prepared by using 1:1 ratio of surfactants mixture which gave the adsorption value of 2.16 mmol/g. Powder X-ray Diffraction indicated that the synthesized organosilica materials are amorphous with improved crystallinity upon attachment of palladium catalyst. The incorporation of palladium in the synthesized materials using the mixed bio-based surfactant was successful.

Catalytic degradation of stable benzene molecules under room temperature conditions over Pt-loaded boron-carbon-nitride (Pt/BCN) catalysts

The catalytic degradation of volatile organic compounds (VOCs) such as benzene via ring-opening at room temperature is challenging due to the presence of π-bonds in the ring-forming carbon atoms. This study involved the preparation of a novel Pt-loaded boron-carbon-nitride (Pt/BCN) catalyst containing single-atom active sites for efficient catalysis of benzene degradation at room temperature in air. The micromorphology, surface structure, and coordination environment of the catalyst were analyzed using characterization techniques including aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC–HAADF–STEM) and X-ray absorption fine structure (XAFS). The degradation mechanism was investigated using electron paramagnetic resonance (EPR) and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). The experimental results demonstrate that Pt/BCN contains many Pt-N4 single-atom active sites that can generate hydroxyl radicals under room-temperature air conditions, leading to the oxidation of benzene to CO2 and H2O. Containing atomically dispersed active-site catalysts developed in this study offer a theoretical foundation for designing catalyst active centers in related fields and advancing the industrial application of room-temperature, low-carbon VOCs treatment technologies.

A detailed characterization study of Ni/CeO2 catalysts identifies Ni availability as the primary factor affecting CO2 methanation performance

The structure of a catalyst has a strong impact on its performance. Here we investigate the physicochemical properties of Ni/CeO2 in an attempt to draw structure–activity relationships for CO2 methanation. A combination of characterisation methods (X-ray diffraction (XRD), 4D Scanning Transmission Electron Microscopy (4D-STEM), CO chemisorption and oxygen storage capacity study etc.) clearly demonstrates the effect of Ni crystallite size, Ni availability (i.e. catalytically accessible Ni) and oxygen vacancies at the Ni-CeO2 interface in Ni/CeO2 during CO2 methanation. Among them, the role of exposed Ni active sites is highlighted, and two possible optimisation schemes i.e. changing the support calcination temperature and the final calcination atmosphere are proposed to obtain a better dispersal of Ni NPs (nanoparticles) on CeO2. Both modification methods do not affect the reaction route, and the activity differences of Ni/CeO2 can be explained by the various hydrogenation rate of formate species, as confirmed by in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) measurements.

A Study of the Influence of Thermoactivated Natural Zeolite on the Hydration of White Cement Mortars.

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally activated natural zeolite on the structural and physical-mechanical characteristics of cured mortars based on white Portland cement and river sand was investigated. The phase compositions were determined by wavelength dispersive X-ray fluorescence (WD-XRF) analysis, X-ray powder diffraction (PXRD), diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and scanning electron microscopy (SEM), as well as thermogravimetric analysis simultaneously with differential scanning calorimetry (TG/DTG-DSC). The results show that the incorporation of zeolite increases the amount of pores accessible with mercury intrusion porosimetry by about 40%, but the measured strengths are also higher by over 13%. When these samples were aged in an aqueous environment from day 28 to day 120, the amount of pores decreased by about 10% and the compressive strength increased by nearly 15%, respectively. The microstructural analysis carried out proves that these results are due to hydration with a low content of crystal water and the realization of pozzolanic reactions that last over time. Replacing some of the white cement with thermally activated natural zeolite results in the formation of a greater variety of crystals, including new crystalline CSH and CSAH phases that allow better intergrowth and interlocking. The results of the investigations allow us to present a plausible reaction mechanism of pozzolanic reactions and of the formation of new crystal hydrate phases. This gives grounds to claim that the replacement of part of the cement with zeolite improves the corrosion resistance of the investigated building solutions against aggressive weathering.

Efficient photocatalytic CO2 and Cr(VI) reduction on carbon spheres/g-C3N4 composites with enriched nitrogen vacancies

In this study, carbon spheres (CS)/g-C3N4 composite materials were fabricated by a hydrothermal method, and the characterizations have confirmed the successful anchoring of CS onto the surface of g-C3N4, constructing enriched nitrogen vacancies during the synthesis process. The photocatalytic CO2 reduction activity of g-C3N4 is enhanced by all of these advantageous factors. The significant enhancement can be attributed to the tight interfacial interaction between CS and g-C3N4, which endows with the photocatalyst a larger specific surface area, higher light utilization efficiency and stronger capability for photoinduced charges separation. Furthermore, the presence of nitrogen vacancies further accelerates the separation and migration efficiency of photogenerated charges, provides additional active sites to promote the adsorption and activation of CO2 molecules, thereby effectively boosting the photocatalytic activity for CO2 reduction. The CO2 conversion rate on CS/g-C3N4 composite materials is higher than that on the reference g-C3N4. The apparent quantum yield (AQY) is also superior to that of the reference g-C3N4 under three different monochromatic light irradiations. The stability of the catalyst was verified through cycling experiments, indicating promising potential practical industrial application. The CO2 reduction mechanism and transformation pathways were elucidated using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The photocatalytic reduction rate constant of Cr(VI) by 50CS/CN is 2.9 times higher than that by CN. This study introduces a facile approach for synthesizing g-C3N4-based photocatalytic materials, providing an interesting strategy to boost photocatalytic activity of g-C3N4 for photocatalytic CO2 and Cr(VI) reduction.

MOF-derived In2O3 nanotubes modified by Bi2Se3 for enhanced NOx detection at room temperature

The In2O3/Bi2Se3 composite was synthesized by loading Bi2Se3 flakes on MOF-derived In2O3 tubes through solvothermal method. The chemical composition, morphology and chemical state of elements for composite were examined through XRD, SEM, TEM and XPS. The In2O3/Bi2Se3 composite exhibited significantly enhanced sensing performance compared to pure In2O3 and Bi2Se3. The response value of In2O3/Bi2Se3 composite is 844 for 30 ppm NOx at 25 °C, which is 21 times that of pure In2O3, and it also displays shorter response /recovery time and lower detection limit. The remarkable gas-sensing properties of In2O3/Bi2Se3 composite are attributable to its large specific surface area, rapid electron mobility, abundant oxygen vacancies and the presence of n-n heterostructure. The adsorption behavior of NOx gas on the surface of In2O3/Bi2Se3 was explored using the in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectrum.

In-situ DRIFTS insights into the evolution of surface functionality of biochar upon thermal air oxidation

Biochar surface functionality is crucial for its application. Herein, the evolution of biochar surface functionality upon thermal air oxidation (TAO) was investigated in-situ by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and thermogravimetric analysis (TGA). The results show that, although the surface functionality of biochar is remarkably changed during TAO at the initial low temperature range, the biochar weight is still stable in the initial low temperature range, suggesting the chemisorption of O2 as intermediate oxygenated functional groups (OFGs) on biochar surface. Moreover, the evolution of biochar surface functionality upon TAO is highly affected on its preparation temperature and intrinsic minerals. Specifically, biochar produced at a high temperature is more resistant to TAO, and more favorable for the formation of ketone groups during TAO. While the biochars prepared at low or medium temperatures show a remarkable formation of carboxyl/lactone groups upon TAO, and the maximum temperature for the formation of carboxyl/lactone groups can be achieved at 400 °C. It's worth noting that the intrinsic minerals in biochar catalyze the TAO reaction, resulting in a much higher mass loss of biochar upon TAO. Furthermore, with the catalysis of intrinsic minerals, TAO is more suitable for enhancing the performance of biochar with intrinsic minerals. These results facilitate the design of engineered biochar via TAO for enhanced applications.

Divergent response of Chernozem organic matter towards short-term water stress in Poa pratensis L. rhizosphere and bulk soil in pot experiments: A spectroscopic study

Understanding and controlling rhizospheric processes under abiotic stress is one of the key challenges in addressing food security amid the climate crisis. In this work, the impact of short-term drought and overwatering on soil organic matter (SOM) of Haplic Chernozem in the rhizosphere of Poa pratensis L. and in bulk soil was investigated. The vegetation experiment was conducted in a climatic chamber at soil moisture levels of 35, 80, and 200 % of the field capacity. UV-Vis and spectrofluorometry were used to describe the water-extractable organic matter (WEOM) characteristics and fluorofores signature, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to describe functional group composition of SOM. Composition and properties of SOM and WEOM of Chernozem significantly change after exposure to short-term water stress. Drought does not affect the composition of rhizosphere SOM except increasing the proportion of polysaccharides, but leads to the decrease in aromaticity and increase in molecular weight of humic-like components of rhizosphere WEOM. These findings reflect Poa adaptation to water deficiency and microbial activity suppression which results in accumulation of SOM intermediate decomposition products. On the contrary, bulk WEOM wasn't affected by drought but SOM became enriched with aromatic and oxidised components. Overwatering leads to equalisation of bulk and rhizospheric SOM composition due to a decrease in the proportion of aromatic and carboxylic components of bulk SOM and the accumulation of microbial products in both bulk and rhizospheric SOM. In general, rhizospheric WEOM undergoes relatively significant changes relative to the optimum water regime under moisture deficit, and bulk WEOM — under overwatering. The findings illustrate the involvement of the both WEOM and SOM in maintaining resilience of the soil-plant system as well as the difference in watering conditions impact on SOM in rhizosphere and bulk soil. SOM spectral data can be used for assessing the state of soil systems, such as changes in microbial activity and adaptation of the soil-plant system to abiotic stress. Our findings also illustrate the differences in the organic matter transformation of the Poa pratensis rhizosphere and the bulk Chernozem depending on environmental factors.

Unraveling high-temperature mechanism of NO + CO reaction on BaO-Y2O3: An in situ DRIFTS and microkinetic study

Understanding high-temperature mechanism of NO reduction by CO on heat-resistant metal oxides is crucial for exhaust aftertreatment systems. We employed the NO + CO light off experiment, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), density functional theory (DFT), and microkinetic study to elucidate the reaction mechanism on BaO-Y2O3 nanocatalyst. The catalytic cycle consisting of “decomposition-oxidation” mode, Mars-van Krevelen (MvK) mechanism, and Langmuir-Hinshelwood (L-H) mechanism is described by in situ DRIFTS and DFT calculations. Their reaction energies and activation barriers are then employed for the microkinetic analysis, revealing that the activity rate is temperature-dependent and aligns with the experimental result. The high-temperature reaction process is primarily governed by the MvK mechanism with rate-determining steps (RDS) of CO + OL ↔ CO2 + Ov, followed by the “decomposition-oxidation” mode. Critically, local CO32- coverage on the BaO surface can facilitate NO and CO adsorption while withstanding the elementary steps such as N2O dissociation and CO oxidation by lattice oxygen. BaCO3-Y2O3 model can be used to interpret the low-temperature reaction process with the RDS of N2O2 ↔ N2O + O, but it impedes reaction kinetics at high temperatures with the rate contribution also predominantly originating from the MvK mechanism. This work provides fundamental insights into how the reaction proceed, and guide the design and optimization of catalysts that can withstand high temperature while maintaining high activity.

Construction of biochar assisted S-scheme of CeO2/g-C3N4 with enhanced photoreduction CO2 to CO activity and selectivity

The multi-interface contacted S-scheme photocatalyst was used for CO2 reduction in this research. A hybrid nanostructures catalyst was constructed using g-C3N4 nanosheet, oxidized CeO2 nanoparticles, and biochar (BIO, cattail-derived). The g-C3N4-BIO/CeO2 catalyst exhibited high selectivity (> 95 %) in converting CO2 to CO in a gas-solid-liquid phase CO2 reduction system. Theoretical and experimental evidence suggests that the multi-interface and interfacial internal electric field (IEF) play a crucial role in enhancing electron transfer and redox ability in CO2 reduction processes. Ce4+ species in CeO2 have the capability to donate two electrons, facilitating the two-electron reduction process involved in the transformation of CO2 to CO. Additionally, Ce4+ in CeO2 acted as an electron trapping agent and could be reduced to Ce3+ ion after trapping electrons, which facilitated the separation process of photogenerated carriers inside CeO2. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrated that COOH* intermediate played a key role as the rate determining step in the overall CO2 photoreduction to CO. This investigation will contribute to the development and application of new and environmentally friendly BIO-based S-scheme photocatalysts.

Combining ACE, PLS-R, and SVM-R for rapid detection of adulteration in saffron samples by diffuse reflectance infrared fourier transform spectroscopy

Accurate estimation of saffron purity is essential for ensuring product integrity, particularly in the presence of common chemical adulterants such as tartrazine, sunset yellow, and quinoline yellow. This study introduces the alternating conditional expectations (ACE) algorithm, coupled with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), as an innovative chemometric approach to address this challenge. The ACE algorithm utilizes optimal transformations for both independent and dependent variables, revealing non-linear relationships and maximizing linear effects between transformed variables. To prepare the spectral data for ACE modeling, we will perform moving average smoothing and Standard Normal Variate (SNV) transformation for preprocessing. Subsequently, we will employ the duplex algorithm to select both calibration and prediction sets from the preprocessed data matrix. The effectiveness of the ACE model was evaluated using several metrics, including the coefficient of determination (R2), adjusted R-squared (R2adj), sum of squared errors (SSE), Regression Sum of Squares (SSR) and mean squared error (MSE). ACE model exhibited excellent performance in determining saffron content even in the presence of adulterants like tartrazine, sunset yellow, and quinoline yellow, on both calibration and prediction sets. Our model achieved excellent performance on both datasets. On the calibration set, a high R2 value (0.9951) indicates a strong correlation between predicted and observed saffron content in the model. The R2adj (0.9950) further strengthens this conclusion by accounting for model complexity, suggesting the model avoids overfitting. These findings are complemented by robustness measures. The statistical parameters of the ACE model, such as total sum of squares (SST) (1.103∗104), SSR (1.098∗104), SSE (54.414), and MSE (0.878), were calculated to compare the performance of the developed methods for determining Saffron's concentration in each mixed sample.

Controlling charge migration and CO2 conversion through surface decoration of 2D-hydrotalcite on bismuth oxybromide for enhanced artificial photosynthesis

Photocatalytic reduction of CO2 in pure H2O media to produce chemicals presents an appealing avenue for simultaneously alleviating energy and environmental crises. However, the rapid recombination of photogenerated charge carriers presents a significant challenge in this promising field. Heterojunction engineering has emerged as an effective approach to address this dilemma. Here, by decorating 2D NiAl-layered double hydroxides (NAL) onto bismuth oxybromide (BOB), we have created a S-scheme heterojunction (N1B1 composite). This catalyst affords CO2-to-CO yields of 102.30 μmol g−1 with a selectivity of 100 %. Ultraviolet photoelectron spectroscopy (UPS) and in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) reveal that charge transfer occurs efficiently from BOB to 2D-NAL upon light irradiation. The designed N1B1 heterojunction achieves 7.3-fold and 2.1-fold increase in the internal electric field strength compared to bare 2D-NAL and BOB, respectively, which should be accountable for the improved charge migration. Additionally, pulsed chemisorption and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) show the presence of multiple carbonate intermediates with activated OCO bonds upon N1B1 composite, with *CO2− being identified as the most crucial species for CO production.

Adsorption of CO2/CH4 on the aromatic rings and oxygen groups of coal based on in-situ diffuse reflectance FTIR

The adsorption mechanisms of CH4 and CO2 on the coal surface is the theoretical basis for CO2 sequestration with enhanced coalbed methane recovery (CO2-ECBM). Molecular simulation is the main method to study the adsorption mechanism at present, but the model used in the process of molecular simulation could not accurately characterize the coal macromolecular structure. Therefore, we used in-situ diffuse reflectance Fourier-transform infrared spectroscopy (FTIR) to study the adsorption of CO2/CH4 on the aromatic rings and oxygen groups of coal. The results showed that CO2 and CH4 were physisorbed on the aromatic rings, and the aromatic rings represented the primary competitive adsorption sites for CO2 and CH4, CO2 was preferentially adsorbed at the top of the aromatic ring compared to CH4. Both carboxyl and carbonyl groups were beneficial for CO2 adsorption but not for CH4 adsorption. Compared to aromatic rings, the adsorption affinity of carboxyl groups for CO2 were stronger. The results of this study revealed the adsorption mechanisms of CO2 and CH4 on the aromatic rings and oxygen groups, as well as the impact of oxygen groups on the gas adsorption capacity, providing a theoretical basis for applying CO2-ECBM in the medium-volatile bituminous coal reservoirs.

Photocatalytic CO2 reduction and destruction of rhodamine B on Bi0/BiOCl with tunable oxygen vacancies induced by 60 CO γ-rays irradiation

In this work, Bi0/OVs-BiOCl photocatalysts were in-situ constructed by irradiating BiOCl with 60Co γ-rays. The powerful penetrating ability of γ-rays induce the Bi-O bonds in BiOCl to break, thereby leading to the deoxygenation (OVs) and the formation of metal Bi0. The presence of Bi0 and OVs endows the photocatalysts with enhanced separation of photogenerated charges and enriched active sites. Under the excitation of simulated sunlight, the BOC-5 sample with an irradiation dosage of 5 KGy demonstrates the best photocatalytic performance, and the yield of CO on the sample is 2.19 μmol·g−1·h−1, which is 2.27 times higher than that on the reference sample. In-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) reveals the formation of intermediates during the conversion of CO2 to CO. Under irradiation of a 300 W xenon lamp, the degradation rate of rhodamine B (RhB) on the BOC-5 sample is 0.05843 min−1, which is 3.42 times of that on the reference sample (0.01708 min−1). The main active species in the degradation process were explored using electron paramagnetic resonance (EPR) and free radical capture experiments at room temperature. This study provides a novel strategy for the preparation of BiOCl-based photocatalysts with high photocatalytic activity through 60Co γ-rays irradiation.