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Aiming at the problem of the poor performance of an Mn-MOF-74-derived Mn 3 O 4 catalyst in low-temperature carbon monoxide (CO) oxidation, copper (Cu) and cerium (Ce) elements were used to modify the Mn 3 O 4 catalyst to improve its performance in low-temperature CO oxidation. According to the results of catalytic performance testing, the CO oxidation activity of the Cu 0.3 Mn 2.7 O 4 catalyst was significantly improved compared with that of the pristine Mn 3 O 4 catalyst, when a CO conversion rate of 90% was achieved at 118 °C. According to X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analyses, the (Mn 2+ + Mn 3+ )/(Mn 2+ + Mn 3+ + Mn 4+ ) ratio and the O ads /O total ratio increased after Cu doping, indicating promoted oxygen vacancy generation. In addition, the increased specific surface area was beneficial for the adsorption of reactant molecules and the exposure of active sites. According to H 2 -temperature-programmed reduction characterization, Cu doping significantly enhanced the performance of the Cu 0.3 Mn 2.7 O 4 catalyst during low-temperature redox. Finally, these factors synergistically promoted the degradation of CO over the Cu 0.3 Mn 2.7 O 4 catalyst. In addition, operando diffuse reflectance Fourier transform infrared spectroscopy results suggested the presence of more terminal-type oxygen, which is essential for the catalytic oxidation of CO on the surface of the Cu 0.3 Mn 2.7 O 4 catalyst. Moreover, the Cu 0.3 Mn 2.7 O 4 catalyst also showed excellent resistance to carbonate, and remarkable stability.

The pressure dependent reaction mechanism of CO 2 hydrogenation over In 2 O 3 was investigated. CO 2 hydrogenation on In 2 O 3 can produce methanol only at high pressure, while the atmospheric pressure operation leads to the formation of CO. The conversion from HCOO* to H 3 CO* is accelerated at high pressure, leading to the formation of methanol with the formate route (CO 2 * → HCOO* → H 3 CO* → H 3 COH).

The pressure dependent reaction mechanism of CO2 hydrogenation over In2O3 was investigated. CO2 hydrogenation on In2O3 can produce methanol only at high pressure, while the atmospheric pressure operation leads to the formation of CO. The conversion from HCOO* to H3CO* is accelerated at high pressure, leading to the formation of methanol with the formate route (CO2* → HCOO* → H3CO* → H3COH). [ABSTRACT FROM AUTHOR]

Anaerobic thermal-assisted photocatalytic methanol conversion in the gas phase in the presence of water vapor has been suggested as an interesting way to generate formaldehyde as a valuable coupled product in addition to H2 production. Here, the reaction mechanism and photocatalyst deactivation are investigated in detail using in situ diffuse reflectance infrared fourier transform (DRIFTS) and electron paramagnetic resonance (EPR) spectroscopy. EPR shows that paramagnetic oxygen vacancies are not involved in the reaction mechanism over undoped SrTiO3. Instead, on an optimized 0.1 wt% Pt/SrTiO3 photocatalyst, methoxy species are formed by dissociative adsorption of methanol leading to formaldehyde formation while the formation of CO, CO2 (via a formate intermediate) and methyl formate occurs through three concurrent reactions from formyl species. Our findings suggest that CO adsorbed on Pt is a spectator species not perturbing the reaction kinetics, and deactivation is shown to be strongly correlated with the accumulation of formate groups on SrTiO3, which is more pronounced at high reaction temperatures. The mechanistic understanding provided here forms the basis for the further optimization of photocatalysts to increase methanol conversion and improve formaldehyde selectivity. [ABSTRACT FROM AUTHOR]

Dendritic plasmonic colloidosome, also known as "black gold", is a unique plasmonic material with broad-spectrum light absorption extending from visible to near-infrared wavelengths. Black gold has demonstrated remarkable performance in challenging and industrially relevant reactions, such as CO2 reduction, alcohol oxidation, acetylene semi-hydrogenation, and purification of seawater. Unfortunately, one of the major shortcomings of black gold lies in its intricate multi-step synthesis procedure. This involves the step-by-step growth of Au nanoparticles on a dendritic fibrous nanosilica (DFNS) support, a task spanning several days. Furthermore, the need for solid separation through centrifugation after each cycle is an additional bottleneck. Consequently, this complexity poses a challenge for industrial scaling. In this work, we report a simplified and efficient one-pot synthesis of plasmonic black gold. The one-pot method streamlines the synthesis process, significantly reducing the time from days to hours and eliminating the need for solid separation steps, thereby enhancing sustainability. Characterization studies reveal the optimal reaction time of an hour (instead of days) during the growth step, resulting in black gold materials closely resembling those synthesized via the conventional cycle-by-cycle method. We further demonstrated that DPC-60 synthesized via a one-pot protocol efficiently catalyzes CO oxidation under light, achieving 87% CO conversion at 4.0 W cm−2 without external heating. In situ DRIFTS studies revealed key adsorption sites involved in the CO oxidation reaction, with bridged CO adsorbed on Au0 sites reacting faster than linearly adsorbed CO, and CO on high-coordinated Au0 sites exhibiting a faster reaction rate than that on low-coordinated sites. Thus, the one-pot synthesis will facilitate rapid exploration of black gold's applications in a range of fields and also pave the way for scalable industrial deployment. [ABSTRACT FROM AUTHOR]

Direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH holds significant economic and environmental value. Numerous catalysts have been employed for this reaction, yet further enhancement of its activity requires a deeper understanding of the catalyst's structure–activity relationship and catalytic mechanism. In this study, we utilized structurally well-defined and highly tunable MOF-808 as a research platform. Functionalizing MOF-808 with ethylenediamine (MOF-808-ED) boosted the space time yield of DMC from 3.25 mmol g−1 h−1 to 7.23 mmol g−1 h−1. The experimental results demonstrate that the reaction involves acid–base synergistic catalysis, where an appropriate balance of acid–base site content is crucial for CO2 and CH3OH to produce DMC, as it facilitates the formation of the key intermediates (CH3OCOO*). Additionally, the nucleophilicity of N is stronger than that of O, further promoting the catalyst's enrichment and activation of CO2. Finally, employing in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) testing, we elucidated the mechanism by which the MOF-808-ED catalyst, with –NH2 as base sites and Zr as acid sites, facilitates the synergistic catalysis of the reaction. This study provides insights into the synergistic effects of acid–base sites on the synthesis of DMC from CO2 and methanol, offering valuable guidance for the development of high-performance catalysts. [ABSTRACT FROM AUTHOR]

To develop high energy density Li batteries, Li metal anodes and in situ plated Li anodes (i.e., the so-called anode-free approach) have been extensively studied. However, the high reactivity of the Li metal surface can lead to chemical reactions with electrolyte components upon contact. Consequently, the so-called native solid electrolyte interphase (SEI) species are formed spontaneously when the Li anode is in contact with the electrolyte. This study illustrates the formation chemistry of native SEI over a Li metal surface using lithium bis(trifluoromethanesulfonyl)imide in tetramethylene sulfone and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (LiTFSI/TMS-TTE) electrolyte with and without lithium polysulfide (PS) additive. All electrolyte components were found to decompose over the Li surface based on diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and ab initio molecular dynamics (AIMD) simulation. The degradation mechanism and the evolved SEI species of each electrolyte component were carefully evaluated. The PS additive can significantly influence the composition of native SEI via its decomposition prior to all other electrolyte components, which can consequently suppress the degradation of the other electrolyte components, namely, TTE, TMS, and LiTFSI. The results indicate the importance of proper selection of electrolyte components, which can lead to the possibility of tuning such native SEI species to stabilize the Li surface in subsequent electrochemical cycling. [ABSTRACT FROM AUTHOR]

CuO/TiO2 catalysts with varying Sb doping ratios were synthesized and applied in the NH3-SCR process. The results of activity tests revealed that the addition of Sb effectively enhanced the performance of low-temperature SCR. Particularly, the CuSbTiOx-0.2 catalyst exhibited the highest activity, achieving over 91% conversion at 250 °C, along with the highest N2 selectivity and exceptional resistance to SO2. Comprehensive characterization analyses demonstrated that CuSbTiOx-0.2 possessed a significantly large specific surface area, the strongest surface acidity, and superior redox performance among the catalysts studied. In situ DRIFTS experiments provided further insights, indicating that Sb modification generated more active species, thereby enhancing the reactivity of ad-NH3 and ad-NOx species. The SCR reaction mechanism for CuSbTiOx-0.2 predominantly followed the Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms. These findings have the potential to advance the development of novel and effective non-vanadium SCR catalysts. [ABSTRACT FROM AUTHOR]

Heterogenized molecular catalysts have shown interesting activities in different chemical transformations. In our previous studies, a molecular catalyst, Re(bpy)(CO)3Cl where bpy is 2,2′-bipyridine, was covalently attached to silica surfaces via an amide linkage for use in photocatalytic CO2 reduction. Derivatizing the bpy ligand with electron-withdrawing amide groups led to detrimental effects on the catalytic activity of Re(bpy)(CO)3Cl. In this study, an alkyl amine linkage is utilized to attach Re(bpy)(CO)3Cl onto SiO2 in order to eliminate the detrimental effects of the amide linkage by breaking the conjugation between the bpy ligand and the amide group. However, the heterogenized Re(I) catalyst containing the alkyl amine linkage demonstrates even lower activity than the one containing the amide linkage in photocatalytic CO2 reduction. Infrared studies suggest that the presence of the basic amine group led to the formation of a photocatalytically inactive Re(I)-OH species on SiO2. Furthermore, the amine group likely contributes to the stabilization of a surface Re(I)-carboxylato species formed upon light irradiation, resulting in the low activity of the heterogenized Re(I) catalyst containing the alkyl amine linkage. [ABSTRACT FROM AUTHOR]

The optimization of electron transfer on Pt–CeO2 (PCH) was achieved by adjusting strong metal–support interaction (SMSI). With an increase in SMSI, there was an initial increase followed by a decline in the concentration of total acid sites and oxygen vacancies (Ov) on PCH. The activity of PCH showed the same trend. Lewis acid is the main acid site of PCH, which facilitates the activation of lattice oxygen and the formation of Pt0 species, which improves the oxygen cycling ability of PCH. Brønsted acid assists in the formation of Ov. PCH450 showed the best co-catalytic activity for toluene and CO due to its highest Brønsted/Lewis acid value (0.211) and abundant Ov. At a 90% conversion rate (T90), the conversion temperature of toluene in mixed pollutants is advanced by 15 °C and that of CO is delayed by 28 °C. The findings of in situ DRIFTS indicated that CO shortens the reaction path of toluene, and toluene reduces the reaction rate of CO. Therefore, CO promotes toluene catalysis on PCH. Despite the competitive adsorption of mixed pollutants in the co-catalytic system, their reaction pathways remain independent. This study provides a theoretical basis for the thermal catalytic technology of industrial waste gas. [ABSTRACT FROM AUTHOR]

A series of copper foam-based monolithic catalysts were prepared by the hydrothermal method, electrophoretic deposition method, and impregnation method using ZIF-67 as a sacrificial template agent. Among them, the Co3O4@CF-H catalyst prepared by the hydrothermal method exhibited excellent toluene catalytic oxidation activity with a T90 (temperature at 90% conversion of toluene) of 218 °C when the weight hour space velocity (WHSV) was 15 000 mL g−1 h−1. The favorable catalytic performance for toluene was maintained even at higher space velocity (WHSV = 60 000 mL g−1 h−1 and T90 = 234 °C) and in an oxygen-poor environment (T90 = 232 °C at 3 vol% O2 content). Particularly, the Co3O4@CF-H catalyst exhibited excellent resistance to CO2 interference and stability. The excellent catalytic performance of the Co3O4@CF-H monolithic catalysts, analyzed in conjunction with a variety of characterization results, was attributed to their strong cobalt–copper interaction, excellent low-temperature reduction and oxygen mobility, as well as the abundance of reactive oxygen and Co3+ species. In situ DRIFTS results revealed that the degradation path of toluene on the Co3O4@CF-H catalyst may be as follows: toluene → benzyl alcohol → benzaldehyde → benzoic acid → maleic anhydride → acetone → CO2 and H2O. DFT calculations illustrated that the loading of Co3O4 and the presence of Cu0 in the copper foam skeleton were both beneficial for improving the catalytic activity. Specifically, it favored the adsorption of oxygen and toluene, and facilitated the dissociation and activation of O2. Overall, this work provides a monolithic catalyst with potential applications for the treatment of VOC exhaust gases. [ABSTRACT FROM AUTHOR]

The effectiveness of photogenerated carrier separation and the restricted number of active sites result in unsatisfactory CO2 photoreduction efficacy. Furthermore, the CO2 photoreduction process always shows the drawback of low product selectivity. Herein, a unique urchin-structured Ga2O3-based photocatalyst with Pd loading was designed and the relationship between the loading amount and the optimal catalytic performance was investigated. Results show that Ga2O3 synthesized at 90 °C with 2% Pd loading amount (2%Pd/Ga2O3-90) gives an excellent yield of up to 107.48 μmol g−1 h−1 and 99.5% selectivity of CH4. The larger specific surface area (44.7 m2 g−1) of Ga2O3 prepared at 90 °C (Ga2O3-90) can provide more active sites, simultaneously, the highly dispersed Pd nanoparticles act as both active sites for CO2 adsorption and activation and as centers for electron capture to facilitate the photogenerated carrier separation effectively. Furthermore, the in situ DRIFTS spectra and CO adsorption isotherm of 2%Pd/Ga2O3-90 confirm the presence of key intermediates such as *CO, and *CHO, indicating that CO can be captured by Pd and further protonated, thereby exhibiting 99.5% selectivity of CH4. This work provides valuable insights into the preparation of catalysts with a high specific surface area and highly selective CO2 photoreduction to CH4. [ABSTRACT FROM AUTHOR]

Humid CO2 adsorption in K+-exchanged zeolites featuring double-eight membered ring (D8R) structures results in CO2 outcompeting and desorbing dimeric water under equilibrated conditions, which is not observed for either the H+-form of the same zeolites or larger-pore zeolites. [ABSTRACT FROM AUTHOR]

Photo-thermal carbon dioxide (CO2) reduction has recently gained significant attention as a strategy to harness solar energy and address environmental challenges. Among other photo-thermal catalysts, indium oxide (In2O3) has emerged as a promising candidate for the CO2 hydrogenation reaction. However, owing to its wide band gap semiconductor nature and relatively low CO2 adsorption capacity, modifications are imperative to facilitate efficient light absorption and CO2 activation. In this study, we report alkali-promoted In2O3 catalysts for efficient and selective photo-thermal CO2 hydrogenation to carbon monoxide (CO). By virtue of the enhanced CO2 adsorption capacity, Cs-promoted In2O3 demonstrated superior catalytic performance with a CO production rate of 28 mmol g−1 h−1 and 100% selectivity under full solar spectrum irradiation and without external heating, which is more than 3 times higher compared to that of pure In2O3. Mechanistic studies indicated that non-thermal effects dominate the reaction pathway, particularly at low reaction temperatures and high light intensities, accompanied by minor pure thermal effects. Additional experiments revealed that the in situ formation of defective sites on the indium oxide catalyst surface under illumination could enhance the light absorption ability, thereby significantly enhancing CO production. Diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrated that light irradiation could stabilize key reaction intermediates and accelerate the CO2 hydrogenation reaction at low temperatures, ultimately boosting CO production compared to dark conditions. [ABSTRACT FROM AUTHOR]

Oxidative dehydrogenation (ODH) of propane is a promising alternative route for propene production. In this work, we developed a series of vanadium and gallium oxides supported on γ-Al2O3 catalysts by an incipient wetness impregnation method. Among the employed catalysts, the VGA-2 showed superior catalytic activity, and the catalyst was demonstrated for longevity in ODH of propane with a stable activity using a continuous flow fixed bed reactor at 400 °C. H2-TPR and UV-visible spectra showed the presence of highly dispersed monomeric VOx species with tetrahedral coordination geometry, which influences product selectivity. The characterization results also conferred that the redox nature of vanadium (V5+ and V4+) oxide and higher V5+ content on the surface of the VGA-2 catalysts are more favourable for C–H activation. In addition, the pyridine-FTIR and 71Ga solid-state NMR studies further substantiated the presence of Lewis acid sites and tetrahedrally coordinated Ga3+Ox species that are highly responsible for the ODHP activity, respectively. Furthermore, in situ-DRIFTS studies conferred that the propane adsorption at ambient temperature showed the formation of intermediate propoxide species with the evolution of σ-bonds and with further increase in the temperature to 325 °C; the stretching vibrations of the ＝C–H and –C–H bonds in the propylene molecule were observed. The spent catalysts were also analyzed by thermogravimetric analysis, where the optimized catalyst (VGA-2) showed the least coke deposition. [ABSTRACT FROM AUTHOR]

Metal halide perovskites with suitable energy band structures and excellent visible-light responses have emerged as promising photocatalysts for CO2 reduction to valuable chemicals and fuels. However, the efficiency of CO2 photocatalytic reduction often suffers from inefficient separation and sluggish transfer. Herein, a step-scheme (S-scheme) CsPbBr3/BiOBr photocatalyst with oxygen vacancies possessing intimate interfacial contact was fabricated by anchoring CsPbBr3 QDs on BiOBr-Ov nanosheets using a mild anti-precipitation method. The results showed that CsPbBr3/BiOBr-Ov-2 with an internal electric field (IEF) heterojunction exhibited a boosted evolution rate of 27.4 μmol g−1 h−1 (CO: 23.8 μmol g−1 h−1 and CH4: 3.6 μmol g−1 h−1) with an electron consumption rate (Relectron) of 76.4 μmol g−1 h−1, which was 5.9 and 3.2 times that of single CsPbBr3 and BiOBr-Ov, respectively. Density functional theory (DFT) calculations revealed that BiOBr with oxygen vacancies can effectively enhance the adsorption and activation of CO2 molecules. More importantly, in situ infrared Fourier transform spectroscopy (DRIFTS) spectra show the transformation process of the surface species, while the femtosecond transient absorption spectrum (fs-TA) reveals the charge transfer kinetics of the CsPbBr3/BiOBr-Ov. Overall, this work provides some guidance for the rational design of S-scheme heterojunctions and vacancy-engineered photocatalysts, which are expected to have potential applications in the fields of photocatalysis and solar energy conversion. [ABSTRACT FROM AUTHOR]

Oxygen vacancy regulation in metal catalysts has emerged as a crucial strategy for efficiently degrading volatile organic compounds (VOCs), while the acquisition of kinetic and mechanistic insights into the oxygen vacancy roles remains highly desirable yet challenging. Herein, we conduct a combined kinetics and mechanistic investigation into the oxygen vacancy effects of Cu catalysts on toluene oxidation. Cu catalysts with varying oxygen vacancy contents are prepared using three representative metal oxide supports, including reducible ZrO2 with strong oxygen storage capacity, reducible ZnO, and unreducible Al2O3. Toluene oxidation and CO oxidation are tested for these catalysts, revealing the superior catalytic activity of the Cu/ZrO2 catalyst. Multiple characterization studies demonstrate that the strong reducibility and abundance of oxygen vacancies within the Cu/ZrO2 catalyst are the key factors for these reactions. A redox-based kinetics strategy is further applied to decouple the reduction and oxidation steps, thus affording a rate diagram to elucidate the promotional effects of oxygen vacancies on toluene decomposition. Additionally, in situ DRIFTS study unveils the reaction pathway, showing the transformation from toluene into benzyl alcohol, benzaldehyde, benzoate, phenol, anhydride, carbonate, and ultimately CO2. As a result, the oxygen vacancy-tuned rate-relevant step is disclosed, shifting from C–H bond cleavage for the Cu/Al2O3 catalyst with limited oxygen vacancies to the C＝O and C＝C bond cleavage for the Cu/ZnO and Cu/ZrO2 catalysts with more oxygen vacancies. The kinetic and mechanistic insights gained here would help guide the design of highly efficient oxidative catalysts by tuning the oxygen vacancies of the support. [ABSTRACT FROM AUTHOR]

BixOyBrz, as a new class of promising layered materials for photocatalysis, have been extensively applied in CO2 reduction. Herein, a series of BixOyBrz with varied Br concentrations were synthesized to probe the contribution of the Br element to the Bi electronic structure, which dominates the conduction band (CB) of BixOyBrz materials. As the O atoms were replaced by the less-electronegative Br, the electronic environment around Bi3+ is altered, further resulting in a shift in the position of the ECB for BixOyBrz. Moreover, Br slabs are interleaved with the [BiO] layers, resulting in increased internal electric field (IEF) strength, which provides a strong driving force for the mobilization of photogenerated carriers. In conjunction with the optimal band structure and efficient carrier separation, BiOBr exhibits the highest catalytic activity with a CO yield of 24.8 μmol g−1. Meanwhile, in situ DRIFTS spectra illustrate the high-proportioned *CO2− active species on BiOBr, indicating the favorable conversion and activation of CO2. This study may provide insights into the role of the Br element in BixOyBrz materials and new opportunities for exploring efficient photocatalysts for CO2 photocatalysis. [ABSTRACT FROM AUTHOR]

We analyzed the effect of the calcination atmosphere and visible-light contribution to an accelerated reaction rate and improved H2 selectivity over 2 wt% Ni/CeO2−x nanorod catalysts. Spectroscopic and structural characterization was performed by operando DRIFTS, in situ Raman, UV-vis and XAS techniques, which were complemented by DFT calculations. Calcination in an argon or H2 atmosphere yields 15% more active catalysts in the thermally driven reaction, which are also more susceptible to light-induced rate acceleration compared to the catalyst calcined in air. The most active 2Ni/CeO2 catalyst calcined in hydrogen converts methane with a rate of 7.5 mmol (gcat min)−1 and produces a H2/CO ratio of 0.6 at 460 °C when stimulated by a combination of visible light and thermal energy. In the absence of visible light illumination and at an identical catalyst temperature, the achieved methane rate was 4.2 mmol (gcat min)−1 and the H2/CO ratio was 0.49. The non-oxidative calcination improves nickel dispersion and the formation of subnanometer sized Ni clusters, together with a higher abundance of surface and bulk oxygen vacancies in ceria nanorods. The Ni–Ov–Ce3+components constitute the catalytically active sites under visible light illumination, which enable the DRM reaction to proceed with an Ea value of 20 kJ mol−1. Visible light also induces the following changes in the 2Ni/CeO2−x catalyst during the DRM reaction: (1) decomposition and desorption of carbonates from the nickel–ceria interface sites, (2) reduced population of nickel surface with carbonyl species and (3) promoted adsorption and dissociation of methane. [ABSTRACT FROM AUTHOR]

By comparing data from an extensive set of Sr and Cr isotope measurements performed on two different thermal ionization mass spectrometers (TIMS), using three sets of Faraday cups with different usage histories, we assess the effects of Faraday cup deterioration on high-precision isotope measurements by TIMS. We find that dynamic 84Sr/86Sr and 87Sr/86Sr measurements provide stable and reproducible results over the entire 56 months of this study, regardless of which set of Faraday cups is used. By contrast, static 84Sr/86Sr and 87Sr/86Sr measurements lead to deviant results, drifts over time, and in general exhibit larger scatter. For the most part, these differences can be attributed to changing Faraday cup efficiencies. For the instruments of this study we find that the center cup is most affected, consistent with this cup often receiving the highest ion beam intensities during measurements conducted in our laboratory. For Cr isotopes, we find that the correlation between mass fractionation-corrected 53Cr/52Cr and 54Cr/52Cr ratios observed for static measurements in several prior studies also reflects different Faraday cup efficiencies. Again, the changing efficiency of predominantly the center cup can account for the observed drift and correlation in 53Cr/52Cr and 54Cr/52Cr. Multi-static Cr isotope measurements reduce this drift, but still result in a residual correlation between the two ratios, suggesting this correlation in part also reflects unaccounted mass fractionation effects. [ABSTRACT FROM AUTHOR]

Constructing mixed-metal nodes and heterojunctions in UiO-66-NH2 (UNH) are two effective strategies to improve the photocatalytic activity and CH4 selectivity in CO2 photoreduction. In this study, ZnO-loaded CeO2 (CeO2/ZnO) was added to the solvothermal synthesis system of UNH, in order to introduce Zn2+ and nano-CeO2 simultaneously into the UNH framework. The XRD, SEM, FT-IR and XPS characterization results proved that Zn2+ partially replaced Zr4+ to form mixed-metal nodes, and the nano-CeO2 was encapsulated in the UNH framework. The optimal catalyst exhibited a CO yield of 22.52 μmol g−1 h−1 and a CH4 yield of 53.18 μmol g−1 h−1 with a CH4 selectivity of 90.42%. The photoelectrochemical characterization and ESR radical trapping experiment results confirmed that Zn-doped UNH was conducive to the enhancement of light utilization, and the direct Z-scheme heterojunction which was constructed between Zn-doped UNH and CeO2 facilitated the separation and migration of photogenerated carriers. The in situ DRIFTS results indicated that the reaction mechanism of CO2 on the catalyst followed the formaldehyde pathway, and the *HCOO species was the key intermediate for CH4 generation. [ABSTRACT FROM AUTHOR]

High transformation of the propane and CO2 reaction to propylene (PDH–CO2) is impelled by the reverse water–gas shift entails strong catalysts toward the reverse water–gas shift (RWGS) as well as propane dehydrogenation (PDH). A series of Co-modified Fe2O3–ZrO2 with proportions of 3–9 wt% (nCoFe–ZrO2) were synthesized using an oxalate coprecipitation method and their catalytic activity for PDH–CO2 at 550 °C was studied. 7CoFe–ZrO2 displayed the highest conversion to both CO2 and propane (37.6% and 47.4%) and propylene yield (38.1%) at a lower apparent activation energy. The interaction between Co species and Fe species and its effects on the active Fe3O4 and the adsorption of propane/CO2 were revealed using XRD, UV-Vis DRS, SEM/TEM, XPS, NH3/CO2/C3H8-TPD, and H2-TPR analysis. With Co-modification, the reduction of Fe2O3 to Fe3O4 was enhanced, which accelerated RWGS in addition to PDH. The key role of the *OOCH intermediate for promoting PDH and RWGS during PDH–CO2 reaction was traced through in situ DRIFTS characterization. [ABSTRACT FROM AUTHOR]

Furfural is a large-volume and widely available biomass-derived platform compound, and its transformation into valuable pentanediols is important for the sustainable production of bio-based polymers. Herein, we report a new catalyst system composed of Pt–Fe bimetallic nanoparticles highly dispersed on a commercial magnesium titanate (MT) support. HAADF-STEM, CO-DRIFTS and XPS characterization studies revealed that Pt was in the metallic state with a particle size of 1–2 nm, while Fe existed as Fe2+ and was decorated on the Pt particles. The electron transfer from Fe to Pt weakened the hydrogenation activity of the furan ring and meanwhile promoted selective ring-opening to 1,2-pentanediol (1,2-PeD). Reaction kinetics studies revealed the reaction rate with respect to hydrogen pressure was close to zero order, which allowed the reaction to proceed at a hydrogen pressure as low as 0.1 MPa. Under mild conditions of 140 °C and 0.1 MPa, the 0.1Pt0.05Fe/MT catalyst offered by far the highest production rate of 178 mol 1,2-PeD per mol Pt per hour, and the Pt–Fe bimetallic catalyst was stable during 200 h of time-on-stream, showing great potential for practical applications. [ABSTRACT FROM AUTHOR]

Reducing the utilization of precious metals and minimizing their depletion has been a pivotal concern in precious metal catalyst research. Hence, we employed a wet impregnation method to fabricate hollow carbon and silicon nanospheres (PdFe/NxC@mSiO2), encapsulating PdFe bimetallic nanoparticles. These bimetallic nanoparticles were enclosed within the hollow spheres, forming an alloy facilitated by nitrogen anchoring. The Pd4Fe1/NxC@mSiO2 catalyst exhibited enhanced dispersion of Pd, strengthened metalcarrier interaction, and superior ability for CO adsorption enrichment compared to single Pd catalysts. In situ DRIFTS analysis further revealed that the PdFe alloy catalysts, prepared via Fe doping, exerted reduced force on CO and improved CO insertion efficiency. Consequently, the Pd4Fe1/NxC@mSiO2 catalyst demonstrated heightened catalytic activity. In comparison to the individual Pd catalyst, this catalyst showed exceptional catalytic activity in the acetylene dialkoxycarbonylation process, with strong selectivity for 1,4-dicarboxylate (485%) and considerable acetylene conversion (490%). Moreover, this catalyst displayed remarkable recyclability, remaining active even after five cycles. [ABSTRACT FROM AUTHOR]

Unlike coal, oil, or natural gas, waste cooking oil (WCO) acts as a renewable source of carbon. It can be converted into energy, fuels, and fine chemicals, instead of being disposed of. This only requires appropriate logistics and a local supply chain network. In such a scenario, WCO can be viewed as a potential feedstock for the production of petrochemicals, particularly critical aromatic platform molecules for high-value chemicals. The study examined, the direct conversion of WCO into aromatic hydrocarbons on an imidazole-supported zeolite (ISZ) catalyst was investigated. The formation of aromatics was found to depend on the pore structure and acidity of the catalyst. The addition of metal oxides over ISZ enhances the Lewis acidic sites, which predominantly enhances the dehydrogenation reaction and yields more aromatic hydrocarbons. In addition, it was found that the average pore size of the catalyst is 6.3 nm, which effectively helps diffuse monoaromatics (C6–C8). To investigate the changes occurring on the catalyst surface during the reaction at different temperatures (25–500 °C), surface intermediates and products formed were closely monitored using in situ DRIFTS. Pyro-probe GC-MS study of the model compounds found in WCO showed that the cracking, cyclisation, and dehydrogenation pathway is responsible for the formation of aromatic hydrocarbons. The Zn20Cr3/ISZ showed excellent stability and good selectivity of C6–C8 aromatic species (65.9%) at 430 °C under atmospheric pressure and promise as a suitable catalyst candidate for high yield aromatics from WCO. [ABSTRACT FROM AUTHOR]

Local microenvironments of the ECO2RR play an important role in tuning the adsorption energy of crucial intermediates, which helps enhance ECO2RR selectivity. Different types of organic polymers were used in this work to modify porous Cu NSs to regulate the local microenvironment and enhance the selectivity of the ECO2RR to C2H4. It is found that when porous Cu NSs are modified with anionic polystyrene vinylbenzyl methylimidazolium chloride (PSMIM), the selectivity of C2H4 reaches (62.34 ± 1.48)%, while the selectivity of C2H4 on the cationic perfluorosulfonic acid polymer Nafion-modified electrode is only (25.41 ± 1.80)%. CO-DRIFTS, in situ ATR-SEIRAS, and molecular dynamics simulation prove that the presence of PSMIM facilitates the adsorption of CO gas and *CO intermediates on the electrode. High *CO coverage is advantageous for the dimerization of *CO, leading to an enhanced selectivity of C2H4. Developing PSMIM-Cu NS electrodes is expected to further accelerate the practical application of porous Cu NSs for the ECO2RR to produce C2H4. [ABSTRACT FROM AUTHOR]

In situ methanol steam reforming for hydrogen production is a promising technology to provide a hydrogen source for full cells. However, the conventional methanol steam reforming usually encounters catalyst inefficiency and instability, which make its industrial application difficult. This work proposes a novel and stable Ni-based catalyst supported by spongy mesoporous alumina and achieves an enhancement of hydrogen production. The prepared Ni/γ-Al2O3 catalyst exhibits a higher hydrogen production yield of 0.26 mol h-1 than the commercial Ni/γ-Al2O3-Com catalyst (0.21 mol h-1) at 450 °C, with an improvement of the hydrogen flow rate of 23.8%. The Ni/γ-Al2O3 catalyst also presents a much superior performance to the reported noble metal-based catalysts and Ni-based catalysts. The special spongy mesoporous structure provides favorable conditions for high catalytic activity, mainly based on the high dispersion of the Ni metal site and the high catalyst stability. The Ni metal particles are highly dispersed over spongy mesoporous Al2O3 with an average particle size of only 3.7 nm. Characterization analysis shows that the spongy mesoporous structure of the catalyst enables quick adsorption of the reactants and reaction intermediates, and the highly dispersed Ni metal site can lead to the rapid dehydrogenation of methanol to increase the hydrogen yield. Moreover, the stability of the prepared Ni/γ-Al2O3-5H catalyst is much superior to that of the commercial Ni/γ-Al2O3-Com catalyst, where Ni/γ-Al2O3-5H retained 100% of methanol conversion for 12 h, and the spongy mesoporous structure and the high dispersion of Ni particles were also well maintained. In addition, the reaction mechanism of methanol steam reforming over the Ni/γ-Al2O3-5H catalyst is revealed in detail, especially based on the in situ DRIFTS characterization results. This research provides valuable insights for the development of catalytic methanol steam reforming for hydrogen production and in the field of green chemistry. [ABSTRACT FROM AUTHOR]

A Ni-based pyrazolate MOF (NiBDP) is studied for SO2 adsorption under static conditions, demonstrating a high SO2 uptake of 8.48 mmol g-1 at 298 K and 1 bar while maintaining a high chemical stability. The influence of Ni(II) coordinatively unsaturated metal sites and coordinated water on the SO2 adsorption performance of this MOF is investigated by using a combination of experimental techniques, including FTIR and in situ DRIFTS measurements, along with Density Functional Theory calculations. The porefilling of the SO2 adsorbates within the material, at the molecular level, is further unravelled through grand Canonical Monte Carlo simulations employing a newly DFT-derived accurate set of force field parameters. [ABSTRACT FROM AUTHOR]

ZSM-5 molecular sieves (ZSM-5-T1, ZSM-5-T2, ZSM-5-T3) were synthesized using SiO2, SiO2-8.7% C, and SiO2-23.6% C as templates from rice husk powder, respectively. Pt species were fixed within the ZSM-5 skeleton via the isovolumetric impregnation method, and the resulting catalysts were employed for the efficient oxidation of toluene (C7H8). Notably, Pt/ZSM-5-T2 exhibited the highest C7H8 catalytic oxidation activity (R175 °C = 0.733 µmol g-1 s-1, WHSV = 60 000 mL h-1 g-1) among the three variants. Furthermore, this catalyst displayed excellent water resistance when exposed to various concentrations of water vapor (2 vol%, 5 vol%, 8 vol% and 10 vol%) during the activity test. The characterization results provided insight into the exceptional catalytic performance of the Pt/ZSM-5-T2 catalyst, attributing it to its high specific surface area, appropriate hydrophilicity, abundant Lewis acid sites, and a high Pt0/(Pt0 + Pt2+) ratio. In situ DRIFTS analysis further suggested that the key step in the oxidation of C7H8 to benzyl alcohol involves C-H cleavage on Pt/ZSM-5. Simultaneously, the application of a life-cycle assessment (LCA) revealed that this strategy, involving the substitution of chemicals with biomass, led to a remarkable 41-43% reduction in carbon footprint. This environmentally friendly approach underscores the potential for repurposing rice husk powder waste. Pt/ZSM-5-T2 meets the requirements for practical applications, paving the way for sustainable resource utilization in the realm of environmental preservation. [ABSTRACT FROM AUTHOR]

The Al(III)-based MOF CYCU-3 exhibits a relevant SO2 adsorption performance with a total uptake of 11.03 mmol g−1 at 1 bar and 298 K. CYCU-3 displays high chemical stability towards dry and wet SO2 exposure. DRIFTS experiments and computational calculations demonstrated that hydrogen bonding between SO2 molecules and bridging Al(III)–OH groups are the preferential adsorption sites. In addition, photoluminescence experiments demonstrated the relevance of CYCU-3 for application in SO2 detection with good selectivity for SO2 over CO2 and H2O. The change in fluorescence performance demonstrates a clear turn-on effect after SO2 interaction. Finally, the suppression of ligand–metal energy transfer along with the enhancement of ligand-centered π* → π electronic transition was proposed as a plausible fluorescence mechanism. [ABSTRACT FROM AUTHOR]

Porous nanoparticles integrating the advantages of porosity and structural coherence typically possess numerous active sites confined on their surfaces. In this study, porous Co3O4, Fe2O3 and Fe3O4 nanoparticles are synthesised by one-step pyrolysis from metal–organic frameworks (MIL-101 (Fe) and ZIF-67 (Co)) to test the performance of CO oxidation. The prepared porous nanoparticles have uniform and stable porous structures without obvious shrinkage and structural collapse. The best catalytic performance was achieved by the porous Co3O4 nanoparticles, which reached 100% CO conversion at 130 °C without any decay in catalytic activity after 48 h of reaction. DRIFTS results present the mechanism of the CO oxidation by porous Co3O4 nanoparticle catalysis. The excellent catalytic activity of the porous Co3O4 nanoparticles is related to the large specific surface area and surface oxygen vacancies. This work provides a design approach for synthesizing other porous metal oxide nanoparticles and has reference value in the field of CO oxidation. [ABSTRACT FROM AUTHOR]

The activation and utilization of the greenhouse gas CO2 is of great interest for the energy transition as a fossil-free carbon source for mitigating climate change. CO2 hydrogenation via the reverse water–gas shift reaction (RWGSR) converts CO2 to CO, a crucial component of syngas, enabling further transformation by means of the Fischer–Tropsch process. In this study, we unravel the detailed mechanism of the RWGSR on low-loaded Au/CeO2 catalysts using IR modulation excitation spectroscopy (MES), by periodically modulating the concentration of the reactants, followed by phase-sensitive detection (PSD). Applying such a MES-PSD approach to Au/CeO2 catalysts during RWGSR gives direct spectroscopic evidence for the active role of gold hydride, bidentate carbonate and hydroxyl species in the reaction mechanism, while disproving the participation of other species such as formate. Our results highlight the potential of modulation excitation spectroscopy combined with phase-sensitive detection to provide new mechanistic insight into catalytic reactions not accessible by steady-state techniques, including a profound understanding of the sequence of reaction steps. [ABSTRACT FROM AUTHOR]

A Cu-based catalyst was developed for one-step solvent-free synthesis of aviation biofuel from biomass-derived ketones, including acetone, cyclopentanone, cyclohexanone, and 2-pentanone. Under the optimal working conditions, the conversion rate of acetone, cyclopentanone, cyclohexanone and 2-pentanone of 100% can be achieved by using Cu/Al2O3. 79.7 c% maximum carbon yield of liquid hydrocarbons with 89.5% selectivity of aviation biofuel was obtained under the conditions of 1.0 MPa H2, 280 °C, and 2 h−1 WHSV. The effects of the calcination temperature on the acidity and basicity of the catalyst, as well as the valence and dispersion of Cu species, were investigated. Based on DFT calculations and in situ DRIFTS results, the preferred adsorption of carbonyl groups and efficient dissociation of hydrogen on Cu+ increased the local concentration of H and feedstock on the catalyst surface, accelerating the rate-determining step that predominated on Cu0. The synergistic effect of Cu0 and Cu+ enhanced the formation of aviation biofuel. [ABSTRACT FROM AUTHOR]

Zr-based UiO-66 metal–organic frameworks are ideal platforms for the design and development of heterogeneous single-atom catalysts (SACs) because of their thermal and chemical stability with the presence of structural defects, enabling the introduction of isolated metal atoms. Elucidating the structure–reactivity relationships and understanding reaction mechanisms for these catalysts are crucial for their industrial applications. We focus here on these aspects for a technically important reaction, preferential CO oxidation (PROX) on a UiO-66-supported Cu SAC by following temperature perturbations in catalytic performance in correlation with changes in the electronic and adsorption properties, which are validated by comprehensive DFT computations. In situ DR-UV-VIS, XANES and NAP-XPS measurements indicated an increase of Cu1+-like states and partial reduction of ZrOx nodes with the increase in reaction temperature, which correlated with a decrease in PROX selectivity. Under similar conditions, DRIFTS measurements revealed a decay of COad adsorption on Cu (i.e., COad@Cu1+ species) and a corresponding red-shift under PROX conditions compared to CO oxidation, suggesting reduction-mediated charge transfer at the Cu–ZrOx interface. In contrast to the CO oxidation cycle which commences by CO adsorption on Cu1+-like sites, DFT computations revealed that the H2 oxidation cycle starts with the reaction of H2 with a pre-adsorbed O2 molecule on Cu1+-like sites, resulting in the generation of a H2O molecule and Cu2+-like sites, which are subsequently reduced to Cu1+-like sites through a successive reaction with a second H2 (or CO) molecule. Adsorption configurations and energies of CO and H2O co-adsorption indicated a competitive adsorption phenomenon on Cu species, which depends on the oxidation state of the Cu ion with a preference for CO adsorption on Cu1+-like sites, while H2O exhibits a stronger affinity for Cu2+-like sites. These results are discussed in terms of the reaction mechanism and PROX selectivity in Cu SAC catalysts and present a model for understanding the catalytic phenomena on MOF-supported SACs. [ABSTRACT FROM AUTHOR]

Higher alcohol synthesis (HAS) from syngas presents an effective method for obtaining clean liquid fuels and high-value chemicals. In this study, we regulated the catalytic performance by altering the dispersion of Rh on the CeO2 support. A comprehensive understanding of the regulatory mechanism of catalytic performance and the key CO adsorption configurations was achieved through a series of characterization experiments. In reduced catalysts, Rh existed in two forms: Rh+ at the Rh–CeO2 interface and Rh0 away from the interface. The total length of the Rh–CeO2 interface perimeter was influenced by the size of Rh nanoparticles, thereby regulating the ratio of Rh0 to Rh+. A balanced distribution of Rh0 to Rh+ is necessary to improve the selectivity, indicating that the synthesis of higher alcohols is contingent upon the synergistic effect of Rh+ and Rh0, and the Rh0–Rh+ sites are identified as the key sites. Furthermore, we clarified the configurations of CO stably adsorbed on the Rh/CeO2 surface under reaction conditions: Rh+2Hx–(CO) and Rh 02– (CO). The C–C coupling between the two adsorbed CO was found to be crucial for the production of higher alcohols. [ABSTRACT FROM AUTHOR]

The ceria-supported nickel catalyst is a widely used benchmark for low-temperature dry reforming of methane (DRM). Nonetheless, whether the atomically dispersed Ni species aggregates during the reaction and which species boost the activity remains elusive. Herein, we designed a group of Ni/CeO2 catalysts ranging from single atoms to nanoparticles (NPs) by carefully increasing the Ni loading from 0.5 to 1.6 wt%. The actual Ni states were verified by a series of advanced characterizations. Through DRM studies, characterizations of reaction-spent Ni species and carbon deposits, kinetics, and time-resolved in situ infrared spectroscopy, we found that the atomically dispersed Ni species aggregate into clusters or NPs upon contact with the DRM reactants, which is necessary for the DRM activity. These in situ aggregated Ni species boosted the overall reaction with less carbon formation, while the reaction-spent 0.5Ni/CeO2 still retaining some single atoms produced more graphitic carbon during the reaction. [ABSTRACT FROM AUTHOR]

Our ability to rationalise the activity of heterogeneous catalytic materials relies on a precise understanding of both the structure and composition of the catalyst under reaction conditions to resolve active sites. Their highly dynamic nature means that catalysis suffers from an observer effect, where the act of measuring activity and/or structure will modify the structure itself. Herein, we present a well-defined catalyst consisting of 2 nm Pt nanoparticles supported on SiO2 that can be dynamically modified and regenerated without irreversibly changing the underlying structure or activity of the catalyst. Using in situ diffuse reflectance infrared Fourier transform spectroscopy and transmission electron microscopy we identify that the catalyst is resistant to oxidative and reductive treatments, but irreversibly restructures in reactive environments (CO + O2) at moderate pressures and temperatures. We show that by using transient pressure pulse experiments it is possible to minimise the restructuring in reactive environments, which when coupled with kinetic modelling can be used to identify site and state dependent activity while simultaneously quantifying the number of active sites. The well-defined nature of this 2 nm Pt/SiO2 catalyst means it can be utilised to gain molecular insight into catalytic processes and act as a new material for use in heterogeneous catalytic surface science. Further, the rapid restructuring of the catalyst during CO oxidation demonstrates that it is not a benign characterisation tool for comparison of catalysts. [ABSTRACT FROM AUTHOR]