Diffuse Reflectance Infrared Fourier Transform Spectra Research Articles

Hierarchically ordered microporous Ag2S QDs-CoOx/NC nanostructures for enhancing photocatalytic CO2 reduction to chemical fuels

Rational design of advanced architectural photocatalysts with efficient separation and transfer of photoinduced charge carriers, and well solar light absorption ability is of critical significance for solar energy utilization and CO2-to-fuel conversion. Herein, a novel three-dimensional (3D) ordered hollow-wall hybrid composite (3DOM Ag2S-CoOx/NC) has been developed by integrating ultrafine Ag2S quantum dots (QDs) on the surface of metal–organic frameworks (MOFs)-derived hierarchically ordered macroporous nitrogen-doped carbon skeletons with implanted CoOx nanoclusters (3DOM CoOx/NC). Compared with pristine 3DOM CoOx/NC and traditional ZIF-67-derived CoOx/NC, the constructed 3DOM Ag2S-CoOx/NC composite exhibits remarkable performances toward the photocatalytic conversion of CO2 and H2O vapor without any sacrifice reagents to fuels (CO-66.00 μmol g−1h−1, CH4-1.21 μmol g−1h−1 and C2H4-2.33 μmol g−1h−1) and a higher C2H4 selectivity (16.47%) in the gas–solid system under light irradiation (λ > 420 nm). Impressively, dual Z-scheme charge transfer pathways in the 3DOM Ag2S-CoOx/NC can provide good channels for boosting electron transfer and charge separation. Experimental characterizations combined with density functional theory (DFT) calculations further elucidate that the key role of Ag2S QDs is served as an auxiliary in the 3DOM Ag2S-CoOx/NC catalyst to improve the electronic structure and further facilitate adsorption/activation capacity of CO2 and H2O. Moreover, the multiple photocatalytic mechanisms including related key intermediates and conversion process of CO2 molecules are further identified by in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). This innovation provides a novel strategy to design well-designed hierarchically porous hybrid structures for photocatalytic CO2 reduction to high-value fuels.

Mesoporous α‑Fe2O3 nanostructures decorated with perovskite Cs3Bi2Br9 quantum dots as an S-scheme photocatalyst for efficient charge transfer and CO2 conversion

In view of the greenhouse effect caused by excessive CO2 emission in the atmosphere, the efficient capture and conversion of CO2 to chemical feedstock is imminent. Herein, a novel Cs3Bi2Br9/α‑Fe2O3 (CBB/α‑Fe2O3) composite was constructed by decorating lead-free perovskite Cs3Bi2Br9 quantum dots (QDs) on the pores of mesoporous α‑Fe2O3 nanostructures. The developed CBB/α‑Fe2O3 composite possesses bifunctional advantages for both the efficient capture and conversion of CO2, with a CO production yield of 84.12 μmol g−1h−1 for the optimized sample. Experimental results and theoretical predictions indicate that the electrons transfer via an S-scheme route in the CBB/α‑Fe2O3 composite, which not only boosts the charge separation but also retains the strong reduction ability of Cs3Bi2Br9. By combination of in-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) with theoretical calculations, the mechanism of the photocatalytic CO2 reduction over the CBB/α‑Fe2O3 composite was explored in depth. This study opens a new avenue for the exploitation of photocatalysts with high CO2 capture ability and conversion efficiency.

Regulating Oxygen Vacancies and Fermi Level of Mesoporous CeO2-x for Intensified Built-In Electric Field and Boosted Charge Separation of Cs3 Bi2 Br9 /CeO2-x S-Scheme Heterojunction.

Regulating the built-in electric field (BEF) in the heterojunction is is a great challenge in developing high-efficiency photocatalysts. Herein, by tailoring the content of oxygen vacancies in the constituent reduction semiconductor (mesoporous CeO2-x ), a precise Fermi level (EF ) regulation of CeO2-x is realized, yielding an amplified EF gap and intensified BEF in the Cs3 Bi2 Br9 perovskite quantum dots/CeO2-x S-scheme heterojunction. Such an enhanced BEF offers a strong driving force for directional electron transfer, boosting charge separation in the S-scheme heterojunction. As a result, the optimized Cs3 Bi2 Br9 /CeO2-x heterojunction delivers a remarkable CO2 conversion efficiency, with an impressive CO production rate of 80.26µmolg-1 h-1 and a high selectivity of 97.6%. The S-scheme charge transfer mode is corroborated comprehensively by density functional theory (DFT) calculations, insitu X-ray photoelectron spectroscopy (XPS), and photo-irradiated Kelvin probe force microscopy (KPFM). Moreover, diffuse reflectance infrared Fourier transform spectra (DRIFTS) and theoretical calculations are conducted cooperatively to reveal the CO2 photoreduction pathway.

Applying DRIFT Spectroscopy for High Temperature Electrochemical Cells-Lessons from SMOX Based Gas Sensors

In operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, the metal oxide sample is illuminated by the infrared beam, and the scattered (rather than transmitted) light is collected with appropriate optics for analysis. In addition to being better suited for operando methods, DRIFT spectroscopy has also been found to be more surface sensitive than other IR techniques suitable for powder samples, such as TIRS, ATR-IRS, and PM-IRRAS.(Roedel et al., 2008) DRIFT spectroscopy has allowed for significant gains in understanding the surface chemistry of semiconducting metal oxide (SMOX) based sensors to be made.Despite the potential usefulness in unravelling different surface mechanisms, ranging from the influence of humidity on the oxygen reduction reaction in fuel cell cathodes to insights about the anodic coking mechanisms when using hydrocarbon fuels, the use of DRIFTs for metal oxide electrochemical cells is still in its infancy, with only a handful of near operando studies being reported. (Cumming et al., 2015; Hauser et al., 2020; Tezel et al., 2022) One critical consideration is the potentially problematic intrinsic IR radiation of samples and the limited stability of cell materials at the high relevant operation temperatures. Nonetheless, using clever cooling systems that prevent the windows from overheating and intricate cell designs to allow for separate oxygen and fuel supply, Cumming et al. and more recently Hauser et al. were able to measure DRIFT spectra at elevated temperatures on cells. (Cumming et al., 2015; Hauser et al., 2020) In both cases, DRIFT spectra were depicted up to 600 ˚C without reports of significant errors due to radiation stemming from the sample. As a result, it is promising that through further optimization, DRIFT spectroscopy could become a useful tool for studying metal oxide based electrochemical systems.For the further optimization, lessons learned during the development of operando cells for SMOX based gases sensors are pertinent. Here a way forward for the optimization will be presented. Starting with practical aspects of DRIFT spectroscopy, e.g. need for precisely controlled room environments in non-evacuated systems or increased signal intensity through window optimization. Common artefacts will be shown, and avoidance strategies will be shown, e.g. ice bands that can be removed through detector evacuation. Additional considerations that are relevant specifically when working with metals oxides will be reviewed and the advantages of selecting the referencing method of Olinger and Griffiths over the traditionally used Kubelka-Munk will be elaborated.(Cumming et al., 2015; Jill M Olinger & Peter R Griffiths, 1988) The usefulness of using isotopically labelled gases to differentiate surface species, e.g. separate metal-oxygen groups from metal-hydroxides, will be discussed. Finally, the potential pitfalls of comparing different samples quantitatively will be highlighted. Overall, this presentation will provide a useful guideline for the future design of an operando DRIFT chamber for oxide based electrochemical cells.BibliographyCumming, D. J., Tumilson, C., Taylor, S. F. R., Chansai, S., Call, A. v., Jacquemin, J., Hardacre, C., & Elder, R. H. (2015). Development of a diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) cell for the in situ analysis of co-electrolysis in a solid oxide cell. Faraday Discussions, 182, 97–111. https://doi.org/10.1039/c5fd00030kHauser, D., Nenning, A., Opitz, A. K., Klötzer, B., & Penner, S. (2020). Spectro-electrochemical setup for in situ and operando mechanistic studies on metal oxide electrode surfaces. Review of Scientific Instruments, 91(8). https://doi.org/10.1063/5.0007435Jill M Olinger, & Peter R Griffiths. (1988). Quantitative effects of an Absorbing Matrix on Near-Infrared Diffuse Reflectance Spectra. Anal. Chem., 60(21), 2427–2435.Roedel, E., Urakawa, A., Kureti, S., & Baiker, A. (2008). On the local sensitivity of different IR techniques: Ba species relevant in NOx storage-reduction. Physical Chemistry Chemical Physics, 10(40), 6190–6198. https://doi.org/10.1039/b808529cTezel, E., Guo, D., Whitten, A., Yarema, G., Freire, M., Denecke, R., McEwen, J.-S., & Nikolla, E. (2022). Elucidating the Role of B-Site Cations toward CO2 Reduction in Perovskite-Based Solid Oxide Electrolysis Cells . Journal of The Electrochemical Society, 169(3), 034532. https://doi.org/10.1149/1945-7111/ac5e9b

Space-Confined Growth of Cs2CuBr4 Perovskite Nanodots in Mesoporous CeO2 for Photocatalytic CO2 Reduction: Structure Regulation and Built-in Electric Field Construction.

Halide perovskites have shown great promise in photocatalytic CO2 conversion. However, their practical application is seriously hindered by severe charge recombination and inadequate adsorption/activation toward CO2 molecules. Herein, the space-confined growth of lead-free Cs2CuBr4 perovskite nanodots in mesoporous CeO2 was realized by a facile impregnation approach. An outstanding CO2 photoreduction performance is achieved by the optimum Cs2CuBr4/CeO2 heterojunction with CO and CH4 yields of 271.56 and 83.28 μmol g-1, respectively. Experimental characterizations and theoretical calculations cooperatively validate the S-scheme charge transfer mechanism in the Cs2CuBr4/CeO2 heterojunction. The CO2 photoreduction pathway is also revealed by combining in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) and density functional theory (DFT) calculations. This study provides useful guidance for the design of high-performance halide perovskite/mesoporous material heterostructure photocatalysts for artificial photosynthesis.

Insights into the formation and stability of soil aggregates in relation to the structural properties of dissolved organic matter from various organic amendments

Organic matter is an important determinant of soil aggregate formation and stability. However, the role of its structure, especially that of dissolved organic matter (DOM) from organic amendments (OAs), in the aggregation process remains imprecise. The purpose of this study was to understand the relationship between the chemical structure of water-extractable organic matter (WEOM), potential source of DOM from OAs, and their aggregate formation/stability functionality through model experiment. The WEOM samples were prepared from bark compost (BC), coffee residue compost (CRC), cattle manure compost (CMC), sewage sludge compost (SSC), fish cake (FC), and rapeseed oil cake (ROC) and characterized using high-performance size exclusion chromatography and 13C nuclear magnetic resonance and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. An upland field soil was packed in glass columns and each WEOM solution or ultrapure water (Control) was applied repeatedly during a 30-day period. Aggregate size distribution (>2000, 500–2000, 250–500, 53–250, and <53 µm) was then measured and aggregate stability indices, mean weight diameter (MWD), and geometric mean diameter (GMD) were calculated. The addition of WEOM increased the distributions of soil mass and soil organic carbon (C) into the > 2000 µm aggregate fraction compared to Control treatment, and the ROC-, CRC-, and SSC-WEOM treatments resulted in greater MWD and GMD than Control and/or the other WEOM treatments. The % O-alkyl C (29–59% of total C) and the relative abundance of high-molecular-weight (HMW) fraction (>10 kDa; 2.3–7.1% of total) in WEOM correlated positively with the proportion of > 2000 µm aggregate fraction. The relative abundance of HMW fraction also correlated positively with MWD. These findings suggest that the high amounts of polysaccharides, suggested by % O-alkyl C and supported by DRIFT spectra, and/or other HMW components are desirable structural characteristics of WEOM for promoting macroaggregate formation and aggregate stability.

New insights into the relationship between Cu–Ce interaction and reactive Cu species in CuOx-CeO2 catalysts for preferential oxidation of carbon monoxide in excess hydrogen

A group of CuOx-CeO2 catalysts for preferential oxidation of carbon monoxide (CO-PROX) is designed by constructing different distribution status of Cu species on similar CeO2 support to adjust the Cu–Ce interaction strength. Cycled temperature programmed reduction by hydrogen (H2-TPR) indicates the strength of Cu–Ce interaction can impact the amount and redox properties of surface highly dispersed CuOx and strongly bonded Cu-[Ox]-Ce species, which respectively determines the catalytic performance at low and high temperature. Temperature programed desorption of H2 (H2-TPD) reveals the presence of large amounts of Cu-[Ox]-Ce species can inhibit H2 adsorption and dissociation, which increases the O2 selectivity toward CO oxidation. Moreover, temperature programmed desorption of CO2 (CO2-TPD) and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) illustrates that H2O and CO2 influences the low-temperature catalytic performance mainly by competitive adsorption with CO on surface highly dispersed reactive Cu+ sites. This work aims to shed light on the underlying Cu–Ce interaction regime, and guide the design of high-performance CuO–CeO2 catalysts in realistic reaction conditions.

Identifying the promotional mechanism for the activity and SO2 resistance of Ce-doped K-OMS-2 for the low-temperature SCR of NO with NH3

Mn-based catalysts for the low-temperature selective catalytic reduction (SCR) of NOx by NH3 can be strongly deactivated due to the generation of MnSO4 derived from upstream SO2 and H2O. In this study, a catalyst architecture based on a Ce-doped manganese oxide octahedral molecular sieve (Ce-OMS-2) was successfully synthesized to promote NH3-SCR activity and enhance SO2 tolerance at low temperatures. We investigated the role of Ce and its specific octahedral molecular sieve structure on the anti-SO2 poisoning effect of Ce-OMS-2. Maintaining the manganese oxide octahedral molecular sieve structure with polyvalent manganese species and active oxygen species and the charge transfer between Mn and Ce via the Ce-O-Mn bond in the Ce-OMS-2 catalyst are found to be the key factors for the realization of excellent NH3-SCR activity and SO2 tolerance. In-depth in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) show that the number of Brønsted acid sites in Ce-OMS-2 can also favor SO2 resistance. This study provides new insight into the mechanism for de-NOx activity and SO2 tolerance on Ce-OMS-2 catalyst and is beneficial for the design of anti-SO2 NH3-SCR catalysts.

DRIFT spectroscopic determination of clay and organic matter in sediment by mixed soil-sediment calibration approach.

Bioavailability and movement of pollutants through land and underground flows are strongly related to some of the sediment characteristics, such as clay minerals and organic matter. Therefore, the determination of clay and organic matter content in sediment is of great importance for environmental monitoring. Clay and organic matter in sediment were determined using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in combination with multivariate analysis methods. Sediment from different depths was used in combination with the soil samples of different texture. Using multivariate methods and DRIFT spectra, sediments from different depths were successfully grouped according to similarity to different texture soils. Also, a quantitative analysis of clay and organic matter content was performed, where a new calibration approach was used in which sediment samples combined with soil samples were used for principal component regression (PCR) calibration. PCR models for the assessment of clay and organic matter were determined for a total of 57 sediment samples and 32 soil samples, and satisfactory determination coefficients were obtained for linear models (0.7136 for clay and 0.7062 for organic matter). The obtained RPD values for both models gave very satisfactory values of 1.9 for clay, i.e., 1.8 for organic matter.

Conversion of Recovered Ammonia and Carbon Dioxide into Urea in the Presence of Catalytically Active Copper Species in Nanospaces of Porous Silica Hollow Spheres.

The present study firstly reported porous silica hollow spheres as a host material for recovery of ammonia and carbon dioxide and conversion of the compounds into urea. These compounds were effectively introduced into the hollow spheres from an aqueous solution including ammonium and carbonate ions accompanied with catalytically active copper ions from the analyses of diffuse reflectance infrared Fourier transform (DRIFT) spectra and diffusion reflectance ultraviolet-visible and near-infrared (DR UV-vis-NIR) spectra. The ammonium and carbonate ions were converted into urea in the hollow spheres at 323 K under 0.5 MPa of argon atmosphere from the results of the DRIFT spectra. From the results of nitrogen sorption isotherms and X-ray photoelectron spectra (XPS) spectra, the amount of the generated urea depended on the amount of the introduced ammonium ions and the size distribution of the nanospaces in the hollow spheres. Urea was highly generated in the hollow spheres with a high amount of ammonium ions and well-ordered nanospaces from the reactants at high density.

Sm-modified Mn-Ce oxides supported on cordierite as monolithic catalyst for the low-temperature reduction of nitrogen oxides

Nitrogen oxides (NOx) are typical atmospheric pollutants that harm the environment and human body, and selective catalytic reduction (SCR) with NH3 is one of the most effective technologies to deal with NOx emissions at present. In this work, a monolithic catalyst, Sm-modified Mn-Ce composite oxides (Sm-MnCe) supported on cordierite (CC), is prepared by impregnation for the first time, and their denitration (de-NOx) performance in NH3-SCR reaction is evaluated in detail. The results show that 0.1Sm-MnCe/CC (Sm/Mn mole ratio is 0.1) has the best de-NOx efficiency with above 80 % NOx conversion from 60° to 270°C, and the high NOx conversion can be maintained within 15 h in the presence of 100 ppm SO2. It is found that appropriate introduction of Sm increases the specific surface area and acid sites, improves the redox environment, elevates the content of Mn4+ on the catalyst surface, which are conducive to the improvement of catalytic activity. In addition, the interaction between active components (Sm, Mn and Ce) also plays a positive role for the excellent de-NOx activity. It is revealed by in-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) that the NH3-SCR reaction over the 0.1Sm-MnCe/CC catalyst follows Eley-Rideal (E-R) and Langmuir-Hinshel (L-H) mechanisms. This work provides ideas for the preparation and modification of monolithic catalysts, which is conducive to promoting the practical industrial application of low-temperature SCR de-NOx technology.

Bimetallic modification of MnFeOx nanobelts with Nb and Nd for enhanced low-temperature de-NOx performance and SO2 tolerance

Nitrogen oxide (NOx) is one of the key factors contributing to air pollution, and selective catalytic reduction with ammonia (NH3-SCR) is widely used for denitrification (de-NOx). To effectively deal with the NOx pollution, it is urgent to develop efficient catalyst working at below 300 °C with a wide operating temperature window. Herein, a series of ferromanganese oxides (MnFeOx) nanobelts are bimetallically modified with niobium (Nb) and neodymium (Nd) for the first time via electrospinning method. The resultant MnFeNbNdOx catalysts present improved low-temperature de-NOx performance and sulfur dioxide (SO2) tolerance, particularly MnFeNb0.2Nd0.1Ox who achieves a NOx conversion up to over 90 % during the range of 120–330 °C and an enhanced tolerance of water (H2O) and SO2. Experimental and theoretical calculations confirm that strong adsorption of nitric oxide (NO) and ammonia (NH3) and weak adsorption of SO2 with the synergy of Nd, Nb and Mn enable MnFeNb0.2Nd0.1Ox excellent SCR activity and good SO2 tolerance. In-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) further reveal that the de-NOx reaction over MnFeNb0.2Nd0.1Ox follows both Eley-Rideal (E-R) and Langmuir-Hinshel-wood (L-H) mechanisms. This study will inspire the further design and study of the synergy of transition metals and rare earth elements for de-NOx.

Where and why do particulate organic matter (POM) and mineral-associated organic matter (MAOM) differ among diverse soils?

Soil organic matter (SOM) has often been separated into operational physical fractions, such as particulate organic matter (POM) and mineral-associated organic matter (MAOM), to improve our understanding of SOM persistence. While it is generally assumed that POM and MAOM have distinct biogeochemical characteristics, it remains unresolved where and why POM and MAOM differ in their composition and relationships to total SOM decomposition among heterogenous soils. We analyzed elemental, isotopic, and chemical composition, including diffuse reflectance infrared Fourier transform (DRIFT) spectra, of POM and MAOM in 156 soil samples collected from 20 National Ecological Observatory Network (NEON) sites spanning diverse ecosystems (tundra to tropics) across North America. We used a classic size separation method for POM (53–2000 μm) and MAOM (<53 μm) following chemical dispersion. Values of C/N, δ13C, and DRIFT spectra for C–H (aliphatic)/CO were correlated and often similar in POM and MAOM fractions across diverse soils; DRIFT spectra for CC (aromatic)/CO were often similar but uncorrelated between fractions. A prevalent hypothesis holds that MAOM is dominated by microbial-derived OM, yet our findings suggest that plant-derived OM can also contribute substantially to MAOM, especially in wet forests receiving >1200 mm annual precipitation (with MAOM C/N > 15). Multiple statistical analyses showed that C quantity and chemical composition of MAOM could as effectively predict soil C decomposition during an 18-month incubation as measures of POM. Thus, POM and MAOM both likely contributed significantly to decomposition over timescales of months, possibly because characteristics of POM and MAOM were often related and/or a large pool size of MAOM could compensate for its lower decomposition rate relative to POM. Further, we found that soil geochemical composition (such as silt and clay, calcium, oxalate-extractable iron and aluminum), along with climate and ecosystem type, could partly predict differences in quantity and composition between POM and MAOM. Overall, relative coupling vs. decoupling between POM and MAOM among soils was predictable based on geochemistry, and these similarities/differences provide insight into variation in the plant-derived sources of MAOM across diverse ecosystems. The importance of MAOM to short-term soil C decomposition has probably been underappreciated.

Alternative flotation collectors for the environmental desulfurization of gersdorffite (NiAsS) bearing mine tailings: Surface chemistry

Environmental desulfurization by froth flotation is a promising technique for the control of acid mine drainage (AMD) and has already been applied in a wide variety of mining operations to prevent environmental risks. This paper aims to address the flotation challenges of gersdorffite for environmental purposes. Gersdorffite, a Ni-As-sulfosalt (NiAsS) frequently encountered in many gold mine wastes, is a major source of contamination. Gersdorffite surface characterization was conducted using diffuse reflectance infrared fourier transform (DRIFT) spectroscopy and optical microscopy, to gain a better understanding of the physicochemical evolution of the mineral surface. The main parameters evaluated were the impact of air-oxidation (aging) and the effect of pH at different values using different reagents (soda ash (NaOH) and lime (CaO)) on the mineral surface chemistry. Collector adsorption behavior was also studied using four collector types as alternatives to xanthate, mainly based on dithiophosphates (DTP) and mercaptobenzothiazole (MBT). Dry grinding of the gersdorffite generated a thin and heterogeneous particle coating mainly composed of arsenic oxides (arsenite and arsenate) and nickel sulfates (NiSO4), with minor elemental sulfur. Hydroxylated Ni species (Ni-OH) were also observed. MBT molecules were found to be the most active compound responsible for the adsorption of the collectors as demonstrated by the adsorption isotherms and the DRIFT spectra. The results of this study have led to a better understanding of gersdorffite surface chemistry before and after the collector adsorption, which should impact its flotation behavior.

Constructing a Pt/YMn2O5 Interface to Form Multiple Active Centers to Improve the Hydrothermal Stability of NO Oxidation.

The hydrothermal stability of NO oxidation is the key to the practical application of diesel oxidation catalysts in diesel engines, which in the laboratory requires that NO activity does not decrease after aging for 10 h with 10% H2O/air at 800 °C. On the one hand, the construction of a metal/oxide interface can lead to abundant oxygen vacancies (Ov), which compensate for the loss of activity caused by the aggregation of Pt particles after aging. On the other hand, YMn2O5 (YMO) has excellent thermal stability and NO oxidation capacity. Therefore, a Pt/YMn2O5-La-Al2O3 (Pt/YMO-LA) catalyst was prepared by the impregnation method. The support of the catalyst, YMn2O5-La-Al2O3 (YMO-LA), was obtained by mixing high specific surface LA and YMO ball-milling. Under laboratory-simulated diesel exhaust flow, the NO oxidation performance of Pt/YMO-LA did not decrease after hydrothermal aging. Combining high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and oxygen temperature-programmed desorption (O2-TPD), the Pt/YMn2O5 interface was formed after hydrothermal aging, and the increased Ov can provide reactive oxygen to Pt and YMO. The cooperative catalysis of multiple active centers composed of Pt, YMO, and Ov is the crucial factor to maintain the NO oxidation performance. In addition, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) show that an increase in Ov is beneficial to the adsorption and desorption of more nitrate and nitrite intermediates, thus achieving the hydrothermal stability of NO oxidation.

Unveiling structure–property relationships of Fe-promoted Rh-Mn/UiO-66-drived catalysts for C2 oxygenates formation from syngas

The effect of iron promoter on the catalytic performance of Rh-Mn/UiO-66-drived catalyst was studied by syngas conversion. The catalysts were completely characterized by means of X-ray diffraction (XRD), N2 sorption, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), diffuse reflectance infrared Fourier transform spectra (DRIFTS), and temperature-programmed surface reaction (TPSR). When the amount of Fe doping reached 0.3 wt%, the catalyst has the excellent catalytic activity with the highest C2+ oxygenates yield of 300.1 g/(kg·h). The results indicated that the appropriate addition of iron can enhance the Rh-Fe interaction, which promote the reduction of Rh active sites. The Rh0-rich state would be observed on the catalysts doped by the appropriate amount of Fe, resulting in the enhancement of CO dissociation ability and strength of the Rh-CO bond, which should be responsible for the higher conversion rate and selectivity of C2+ oxygenates.

Unveiling the effect of interstitial dopants on CO2 activation over CsPbBr3 catalyst for efficient photothermal CO2 reduction

Halide perovskites, enabled by their superior light harvesting ability and high carrier mobility, have emerged as promising catalysts for solar CO2 reduction. However, the catalytic performance remains largely limited due to the challenge of efficient CO2 activation on pristine perovskite surface. Herein, we elaborately doped the CsPbBr3 with interstitial Cu ions to reveal the effect of dopants on the CO2 activation for photothermal CO2 reduction using H2O as the proton source. Initially, the interstitial Cu dopants would significantly suppress the charge carrier recombination in CsPbBr3, leaving more carriers to participate in the surface catalytic reactions. Meanwhile, the Cu dopants would modulate the surface sites for better adsorption and activation of CO2 molecules and CO intermediates, as evidenced by the results of CO2 and CO temperature-programed-desorption profiles. Furthermore, analysis of in-situ diffuse-reflectance infrared Fourier transform spectra (DRIFTS) and theoretical calculations indicates that the CO2 reduction to CH4 follows *COH pathway on Cu:CsPbBr3, but *CHO pathway on CsPbBr3, where the former is more thermodynamically favorable. It is then revealed that the Cu dopants would facilitate the CO2 reduction by supplying more carriers, adsorbing more CO2 molecules and catalyzing the CO2 dissociation more easily. As a result, our Cu:CsPbBr3 achieved an impressive activity of 14.72 μmol·g−1·h−1 for CH4 production and a CH4 selectivity of 96.9%, which are both higher than those of the pristine CsPbBr3 (3.62 μmol·g−1·h−1 and 81.1%). Our work provides an insightful understanding of the roles of dopants in the CO2 activation for photothermal catalytic CO2 reduction on halide perovskite catalysts.

Acrylonitrile and Pullulan Based Nanofiber Mats as Easily Accessible Scaffolds for 3D Skin Cell Models Containing Primary Cells.

(1) Background: Three-dimensional (3D) collagen I-based skin models are commonly used in drug development and substance testing but have major drawbacks such as batch-to-batch variations and ethical concerns. Recently, synthetic nanofibrous scaffolds created by electrospinning have received increasing interest as potential alternatives due to their morphological similarities to native collagen fibrils in size and orientation. The overall objective of this proof-of-concept study was to demonstrate the suitability of two synthetic polymers in creating electrospun scaffolds for 3D skin cell models. (2) Methods: Electrospun nanofiber mats were produced with (i) poly(acrylonitrile-co-methyl acrylate) (P(AN-MA)) and (ii) a blend of pullulan (Pul), poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) (Pul/PVA/PAA) and characterized by scanning electron microscopy (SEM) and diffuse reflectance infrared Fourier transform (DRIFT) spectra. Primary skin fibroblasts and keratinocytes were seeded onto the nanofiber mats and analyzed for phenotypic characteristics (phalloidin staining), viability (Presto Blue HS assay), proliferation (Ki-67 staining), distribution (H/E staining), responsiveness to biological stimuli (qPCR), and formation of skin-like structures (H/E staining). (3) Results: P(AN-MA) mats were more loosely packed than the Pul/PVA/PAA mats, concomitant with larger fiber diameter (340 nm ± 120 nm vs. 250 nm ± 120 nm, p < 0.0001). After sterilization and exposure to cell culture media for 28 days, P(AN-MA) mats showed significant adsorption of fetal calf serum (FCS) from the media into the fibers (DRIFT spectra) and increased fiber diameter (590 nm ± 290 nm, p < 0.0001). Skin fibroblasts were viable over time on both nanofiber mats, but suitable cell infiltration only occurred in the P(AN-MA) nanofiber mats. On P(AN-MA) mats, fibroblasts showed their characteristic spindle-like shape, produced a dermis-like structure, and responded well to TGFβ stimulation, with a significant increase in the mRNA expression of PAI1, COL1A1, and αSMA (all p < 0.05). Primary keratinocytes seeded on top of the dermis equivalent proliferated and formed a stratified epidermis-like structure. (4) Conclusion: P(AN-MA) and Pul/PVA/PAA are both biocompatible materials suitable for nanofiber mat production. P(AN-MA) mats hold greater potential as future 3D skin models due to enhanced cell compatibility (i.e., adsorption of FCS proteins), cell infiltration (i.e., increased pore size due to swelling behavior), and cell phenotype preservation. Thus, our proof-of-concept study shows an easy and robust process of producing electrospun scaffolds for 3D skin cell models made of P(AN-MA) nanofibers without the need for bioactive molecule attachments.

Promotional effect of Cu additive for the selective catalytic oxidation of n-butylamine over CeZrOx catalyst

The catalytic elimination of nitrogen-containing volatile organic compounds (NVOCs) still encounters bottlenecks in NOx formation and low N2 selectivity. Here, a series of Cu-promoted Ce-Zr mixed oxide catalysts were synthesized using a simple precipitation approach, and n-butylamine was adopted as the probe pollutant to evaluate their catalytic performance. The CeCu10%ZrOx catalyst exhibited the best catalytic activity, with 100% n-butylamine conversion and 90% N2 selectivity at 250 °C. Concurrently, this sample also displayed good water resistance. A detailed characterization of the catalyst was performed through a series of experimental studies and theoretical calculations. The addition of Cu increased the redox property and promoted the production of oxygen vacancies, all of which were favorable for the greatest n-butylamine selective catalytic oxidation performance. The changes of oxygen vacancies over CeCu10%ZrOx in reaction process were studied by in situ Raman spectra. Moreover, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) and theoretical calculations were employed to explore the reaction mechanism of n-butylamine selective oxidation. The high activity and selectivity of this catalyst confirm the practical feasibility of the selective oxidation of n-butylamine to CO2 and N2, and the exploration of the reaction mechanism provides new insights into the further design of catalysts.

Role of water on ozonation of cinnamaldehyde to benzaldehyde under Ca(OH)2 catalysis: A combined in situ DRIFTS and DFT study

The role of water on cinnamaldehyde ozonation to benzaldehyde under Ca(OH)2 catalysis was studied by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) and Density Function Theory (DFT). According to the thermogravimetry results, the water, generated in the ozonation, reacted with CaO to form Ca(OH)2 and then existed on the Ca(OH)2 surface in the form of adsorbed and interlayer water. The experiment results showed that lab-made and pre-processed Ca(OH)2 had better catalytic activities because their specific surface area values were 3.59 and 4.46 times larger than CaO. DFT results indicated that the competitive adsorption between water and ozone was weak due to the difference of their average adsorption energy difference. The major effect of water was to promote ozonide decomposition and ·OH formation. At the presence of water, the DRIFTS signals of physisorption ozone and ozonide disappeared within 20 min, but the signals of oxygen atoms and O2– had about 12% and 33% increasing, respectively. As the water content increased in the system and the key intermediates, ozonides, and ·OH, changed, the ozonation mechanism was changed from the Criegee mechanism to the free radical mechanism, resulting in a significant decrease in the selectivity of benzaldehyde.