New Application of Z‑Scheme Ag₃PO₄/g‑C₃N₄ Composite in Converting CO₂ to Fuel

This research was designed for the first time to investigate the activities of photocatalytic composite, Ag₃PO₄/g-C₃N₄, in converting CO₂ to fuels under simulated sunlight irradiation. The composite was synthesized using a simple <i>in situ</i> deposition method and characterized by various techniques including Brunauer–Emmett–Teller method (BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and an electrochemical method. Thorough investigation indicated that the composite consisted of Ag₃PO₄, Ag, and g-C₃N₄. The introduction of Ag₃PO₄ on g-C₃N₄ promoted its light absorption performance. However, more significant was the formation of heterojunction structure between Ag₃PO₄ and g-C₃N₄, which efficiently promoted the separation of electron–hole pairs by a Z-scheme mechanism and ultimately enhanced the photocatalytic CO₂ reduction performance of the Ag₃PO₄/g-C₃N₄. The optimal Ag₃PO₄/g-C₃N₄ photocatalyst showed a CO₂ conversion rate of 57.5 μmol<b>·</b>h^–1<b>·</b>g_cat^–1, which was 6.1 and 10.4 times higher than those of g-C₃N₄ and P25, respectively, under simulated sunlight irradiation. The work found a new application of the photocatalyst, Ag₃PO₄/g-C₃N₄, in simultaneous environmental protection and energy production

Hydrogen-Bonding Interactions in Pyridinium-Based Ionic Liquids and Dimethyl Sulfoxide Binary Systems: A Combined Experimental and Computational Study

The addition of highly polar and aprotic cosolvents to ionic liquids has proven to considerably decrease the viscosity of the solution and improve mass transfer in many chemical reactions. In this work, the interactions between a representative pyridinium-based ionic liquid, N-butylpyridinium dicyanamide ([Bpy]­[DCA]), and a cosolvent, dimethylsulfoxide (DMSO), were studied in detail by the combined use of attenuated total reflection Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (1H NMR), and density functional theory calculations. Several species in the [Bpy]­[DCA]–DMSO mixtures have been identified, that is, ion clusters can translate into ion pairs during the dilution process. DMSO formed hydrogen bonds (H bonds) simultaneously with [Bpy]+ cations and [DCA]− anions but stronger hydrogen-bonding interactions with the [Bpy]+ cations than the [DCA]− anions, and the intrinsic hydrogen-bond networks of IL were difficult to interrupt at low DMSO concentrations. Interestingly, hydrogen-bonding interactions reach the strongest when the molar fraction of DMSO is 0.4–0.5. Hydrogen-bonding interactions are prominent in the chemical shifts of hydrogen atoms in [Bpy]+ cations, and anisotropy is the main reason for the upfield shifts of DMSO in the presence of [Bpy]­[DCA]. The theoretical calculations offer in-depth studies of the structural evolution and NMR calculation

On the CO₂ Capture in Water-Free Monoethanolamine Solution: An ab Initio Molecular Dynamics Study

Monoethanolamine (MEA) based liquids are widely used materials for postcombustion CO₂ capture. We report here an extensive ab initio molecular dynamic (AIMD) simulation study on CO₂ sorption in water-free MEA liquid with a range of CO₂ contents at 313 K. The simulation reveals the detailed CO₂ capture mechanism that leads to the initial formation of a zwitterion species and the ultimate proton transfer from the zwitterion to a nearby MEA molecule. The ion pairs formed in the liquid result in strong electrostatic interactions among the molecules in the liquid. The variation of liquid density, volume, diffusion coefficient, power spectrum, and average heat of sorption at the selected CO₂ loadings was systematically assessed. The results indicate that initially the volume of the MEA solution expands gradually and tops at 60% of CO₂ loading. After that, the volume declines as a result of strong Coulomb interactions among the ion pairs at higher CO₂ loadings. The calculated liquid densities and the average heats of sorption are in quantitative agreement with the available experimental values. The simulated power spectrum of the water-free liquid also resembles the infrared spectrum of 30% aqueous MEA solution. The characteristic features in the simulated power spectra are slightly blue-shifted upon CO₂ uptake

Theoretical DFT Study on the Mechanisms of CO/CO₂ Conversion in Chemical Looping Catalyzed by Calcium Ferrite

The CO/CO2 conversion mechanism on the calcium ferrite (CFO) surface in chemical looping was explored by a computational study using the density functional theory approach. The CFO catalytic reaction pathway of 2CO + O2 → 2CO2 conversion has been elucidated. Our results show that the Fe center in CFO plays the key role as a catalyst in the CO/CO2 conversion. Two energetically stable spin states of CFO, quintet and septet, serve as the effective catalysts. The presence of the triplet O2 molecule caused the conversion of these two spin-state structures into each other along the catalytic reaction pathway. A double release of CO2 was predicted following this reaction mechanism. The rate-determining step is the formation of the 2CO2–CFO complex (P4) in the quintet state (19.0 kcal/mol). The predicted energy barriers for all the steps suggest that the proposed pathway is plausible

Mechanistic Study on Water Gas Shift Reaction on the Fe₃O₄ (111) Reconstructed Surface

We present a first-principles study using periodic density functional theory on a water gas shift reaction on a Fe_oct2‑tet1-terminated Fe₃O₄ (111) surface. We show that water can easily undergo dissociative adsorption to form OH and H adatom species on the surface. Three possible reaction mechanisms (i.e., redox mechanism, associative mechanism, and coupling mechanism) were systematically explored based on minimum energy path calculations. It was identified that the redox mechanism is the energetically most favorable pathway for the water gas shift reaction on the Fe_oct2‑tet1-terminated Fe₃O₄ (111) surface. The COO* desorption was found to be the rate-limiting step with a barrier of 1.04 eV, and the OH dissociation has the second-highest activation barrier (0.81 eV). Our results are consistent with results of kinetic and isotope exchange experiments. Our studies suggest that it is necessary to develop a promoter to reduce the activation barriers of the COO* desorption and OH dissociation steps in order to improve the catalyst performance

Chemical Degradation of Drinking Water Disinfection Byproducts by Millimeter-Sized Particles of Iron−Silicon and Magnesium−Aluminum Alloys

Chemical Degradation of Drinking Water Disinfection Byproducts by Millimeter-Sized Particles of Iron−Silicon and Magnesium−Aluminum Alloy

Ethane Dehydrogenation over the Core–Shell Pt-Based Alloy Catalysts: Driven by Engineering the Shell Composition and Thickness

Pt-based catalysts as the commercial catalysts in ethane dehydrogenation (EDH) face one of the main challenges of realizing the balance between coke formation and catalytic activity. In this work, a strategy to drive the catalytic performance of EDH on Pt–Sn alloy catalysts is proposed by rationally engineering the shell surface structure and thickness of core–shell Pt@Pt3Sn and Pt3Sn@Pt catalysts from a theoretical perspective. Eight types of Pt@Pt3Sn and Pt3Sn@Pt catalysts with different Pt and Pt3Sn shell thicknesses are considered and compared with the industrially used Pt and Pt3Sn catalysts. Density functional theory (DFT) calculations completely describe the reaction network of EDH, including the side reactions of deep dehydrogenation and C–C bond cracking. Kinetic Monte Carlo (kMC) simulations reveal the influences of the catalyst surface structure, experimentally related temperatures, and reactant partial pressures. The results show that CHCH* is the main precursor for coke formation, and Pt@Pt3Sn catalysts generally have higher C2H4(g) activity and lower selectivity compared to those of Pt3Sn@Pt catalysts, which is attributed to the unique surface geometrical and electronic properties. 1Pt3Sn@4Pt and 1Pt@4Pt3Sn are screened out as catalysts exhibiting excellent performance; especially, the 1Pt3Sn@4Pt catalyst has much higher C2H4(g) activity and 100% C2H4(g) selectivity compared to those of 1Pt@4Pt3Sn and the widely used Pt and Pt3Sn catalysts. The two descriptors C2H5* adsorption energy and reaction energy of its dehydrogenation to C2H4* are proposed to qualitatively evaluate the C2H4(g) selectivity and activity, respectively. This work facilitates a valuable exploration for optimizing the catalytic performance of core–shell Pt-based catalysts in EDH and reveals the great importance of the fine control of the catalyst shell surface structure and thickness

Factors Affecting Ionic Liquids Based Removal of Anionic Dyes from Water

Liquid−liquid extraction with imidazolium based ionic liquids[C4mim][PF6], [C6mim][PF6], [C6mim][BF4], and [C8mim][PF6]is proposed for removal of anionic dyes including methyl orange, eosin yellow, and orange G from aqueous solutions. The effects of extraction time, pH of aqueous phase, structure of the ionic liquids, temperature, and KCl concentration on the extraction efficiencies have been studied. Extraction efficiencies of dyes were strongly affected by the pH of the aqueous phase. Under the optimized pH condition, 85−99% of methyl orange, almost 100% eosin yellows, and 69% of orange G in tested water samples were transferred into the ionic liquids in a single extraction. Extraction efficiency for a given dye was found to increase with increasing temperature and increasing alkyl chain length of cation of the ionic liquids. Presence of a small amount of KCl in the aqueous phase did not considerably improve the extraction efficiency of the dyes. Thermodynamic studies revealed that the extraction process was driven by hydrophobic interaction of the anionic dyes and the ionic liquids