High-Performance Integrated rGO-[Polymeric Ionic Liquid] [Heteropolyanions] for Catalytic Degradation of Azo Dyes

Polymeric ionic liquid (such as poly[ViEtIm]Br)-modified reduced graphene oxide (rGO), rGO-poly[ViEtIm]Br, was nominated as an open carrier to construct a degradation platform. The large specific surface of rGO together with the anion-exchange property of poly[ViEtIm]Br terminals led to the wide growth of heteropolyanions (like [PW12O40]3–, [PMo12O40]3–, and [SiW12O40]4–), thus assembling the integrated catalyst rGO-poly[ViEtIm][heteropolyanions]. The grafted poly[ViEtIm]Br provided an anchor point to interlink the polar heteropolyanions and the nonpolar rGO substrate, endowing this graphene-based catalyst with excellent dispersibility. The adequate exposure of heteropolyanions further promoted the decolorization capability during the degradation procedure. Morphology, structure, and properties of materials were confirmed and monitored via transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) spectroscopy, etc. rGO-poly[ViEtIm][PW12O40] was selected as the optimal catalyst with degradation efficiency toward methyl orange reaching 98.7% in 3 h. In addition, the excellent structural stability of the catalyst improved the decolorization efficiency, which reached 95% after recycling five times

Theoretical Study on the Mechanism and Kinetics for the Self-Reaction of C₂H₅O₂ Radicals

Oxygen-to-oxygen coupling, direct H-abstraction and oxygen-to-(α)­carbon nucleophilic substitution processes have been investigated for both the singlet and triplet self-reaction of C₂H₅O₂ radicals at the CCSD­(T)/cc-pVDZ//B3LYP/6-311G­(2d,2p) level to evaluate the reaction mechanisms, possible products and rate constants. The calculated results show that the title reaction mainly occurs through the singlet oxygen-to-oxygen coupling mechanism with the formation of entrance tetroxide intermediates, and the most dominant product is C₂H₅O + HO₂ + CH₃CHO (P5) generated in channel R5. Beginning from the radical products of P5 (C₂H₅O, HO₂) and reactant (C₂H₅O₂), five secondary reactions HO₂ + HO₂ (a), HO₂ + C₂H₅O (b), C₂H₅O + C₂H₅O (c), HO₂ + C₂H₅O₂ (d), and C₂H₅O + C₂H₅O₂ (e) mainly proceed on the triplet potential energy surface. Among these reactions, (a), (b), and (d) are kinetically favorable because of lower barrier heights. The calculated rate constants of channel R5 between 200 and 295 K are almost independent of the temperature, which is in agreement with the experimental report. With regard to the final products distribution, CH₃CHO, C₂H₅OH, C₂H₅OOH, H₂O₂, and ³O₂ are predicted to be major, whereas C₂H₅OOC₂H₅ should be in minor amount

Enhancing Electrocatalytic Water Oxidation of NiFe-LDH Nanosheets via Bismuth-Induced Electronic Structure Engineering

The design and synthesis of high-efficiency electrocatalysts are of great practical significance in electrocatalytic water splitting, specifically in accelerating the slow oxygen evolution reaction (OER). Herein, a self-supported bismuth-doped NiFe layered double hydroxide (LDH) nanosheet array for water splitting was successfully constructed on nickel foam by a one-step hydrothermal strategy. Benefiting from the abundant active sites of two-dimensional nanosheets and electronic effect of Bi-doped NiFe LDH, the optimal Bi0.2NiFe LDH electrocatalyst exhibits excellent OER performance in basic media. It only requires an overpotential of 255 mV to drive 50 mA cm–2 and a low Tafel slope of 57.49 mV dec–1. The calculation of density functional theory (DFT) further shows that the incorporation of Bi into NiFe LDH could obviously overcome the step of H2O adsorption during OER progress. This work provides a simple and effective strategy for improving the electrocatalytic performance of NiFe LDHs, which is of great practical significance

The catalytic effects of H₂CO₃, CH₃COOH, HCOOH and H₂O on the addition reaction of CH₂OO + H₂O → CH₂(OH)OOH

<p>The addition reaction of CH₂OO + H₂O <b>→</b> CH₂(OH)OOH without and with X (X = H₂CO₃, CH₃COOH and HCOOH) and H₂O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH₂OO + H₂O → CH₂(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH₂OO···H₂O is favourable one. Water-assisted CH₂OO + H₂O → CH₂(OH)OOH can occur by H₂O moiety of (H₂O)₂ or the whole (H₂O)₂ forming cyclic structure with CH₂OO, where the latter form is more favourable. Because the concentration of H₂CO₃ is unknown, the influence of CH₃COOH, HCOOH and H₂O were calculated within 0–30 km altitude of the Earth's atmosphere. The results calculated within 0–5 km altitude show that H₂O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%–77.26% and 0.04%–1.76%. Within 5–30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%–98.28%. However, compared with the reaction of CH₂OO + HCOOH, the rate of CH₂OO···H₂O + HCOOH is much slower.</p

Influence of H₂SO₄···H₂O and (H₂SO₄)₂ on the Hydrolysis of Formaldehyde: A Potential Source of Methanediol in the Troposphere

The hydrolysis of formaldehyde [HCHO + H2O → H2C(OH)2] assisted by bimolecular acidic catalyst of X (X = H2SO4···H2O and (H2SO4)2) under different concentrations of H2SO4 and H2O was performed by quantum chemical calculations of CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/6-311++G(3df,3pd) and the master equation method. The calculated results show that the hydrolysis reaction of HCHO catalyzed by X can occur through both HCHO···H2O + X (one-step reaction) and H2O···X + HCHO (stepwise reaction) routes. The stepwise reaction assisted by H2SO4···H2O is the most favorable reaction among all the hydrolysis reactions assisted by X, with its effective rate constant larger by at least 2 orders of magnitude. In comparison with the hydrolysis of HCHO without X, the favorable route for the hydrolysis of HCHO with H2SO4···H2O can reduce the energy barrier by 32.0 kcal·mol–1. Meanwhile, the energy barrier of this reaction is also lower by another 0.8–17.6 kcal·mol–1 than those of the hydrolysis reaction of HCHO assisted by H2SO4, HCOOH, HNO3, CH3COOH, H2O, and (H2O)2. From the viewpoint of the calculated effective rate constant k′, the hydrolysis of HCHO with H2SO4···H2O {[H2SO4] = 106 molecules·cm–3 and [H2O] at 40–100% relative humidity (RH) along with [H2SO4] = 107–108 molecules·cm–3 and [H2O] at 20–100% RH} is more effective than the hydrolysis reaction assisted by H2O, (H2O)2, HCOOH (0.01–10 ppbv), HNO3 (109–1011 molecules·cm–3), and CH3COOH (1–5 ppbv) within the temperature range of 280–320 K. Under the same condition, the hydrolysis of HCHO with H2SO4···H2O can compete well with the hydrolysis of HCHO assisted by H2SO4 (106–108 molecules·cm–3). Therefore, this work predicts that H2SO4···H2O can play a significant role in the hydrolysis of HCHO in the condition of wet areas with relatively high H2SO4 pollution