Photocatalytic CO2 reduction with iron porphyrin catalysts and anthraquinone dyes.

Herein we studied visible-light-driven CO2 reduction using a series of tetra-phenylporphyrin iron catalysts and inexpensive anthraquinone dyes. Varying the functional groups on the phenyl moieties of the catalysts significantly enhances the photocatalytic activity, achieving an optimal turnover number (TON) of 10 476 and a selectivity of 100% in the noble-metal-free systems. The highest activity found in a bromo-substituted catalyst is attributed to favorable electron transfer from the photosensitizer to the iron porphyrin.

Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution.

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L-1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV-vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

Surface Hydroxyl and Oxygen Vacancies Engineering in ZnSnAl LDH: Synergistic Promotion of Photocatalytic Oxidation of Aromatic VOCs.

Photocatalytic oxidation has gained great interest in environmental remediation, but it is still limited by its low efficiency and catalytic deactivation in the degradation of aromatic VOCs. In this study, we concurrently regulated the surface hydroxyl and oxygen vacancies by introducing Al into ZnSn layered double hydroxide (LDH). The presence of distorted Al species induced local charge redistribution, leading to the remarkable formation of oxygen vacancies. These oxygen vacancies subsequently increased the amount of surface hydroxyl and elongated its bond length. The synergistic effects of surface hydroxyl and oxygen vacancies greatly enhanced reactant adsorption-activation and facilitated charge transfer to generate •OH, •O2-, and 1O2, resulting in highly efficient oxidation and ring-opening of various aromatic VOCs. Compared with commercial TiO2, the optimized ZnSnAl-50 catalyst exhibited about 2-fold activity for the toluene and styrene degradation and 10-fold activity for the chlorobenzene degradation. Moreover, ZnSnAl-50 demonstrated exceptional stability in the photocatalytic oxidation of toluene under a wide humidity range of 0-75%. This work marvelously improves the photocatalytic efficiency, stability, and adaptability through a novel strategy of surface hydroxyl and oxygen vacancies engineering.

A Pilot Nationwide Survey on the Concentrations of Neonicotinoids and Their Metabolites in Indoor Dust from China: Application for Human Exposure.

The present study assessed the residue levels of six parent neonicotinoids (p-NEOs) and four metabolites (m-NEOs) in indoor dust collected from 12 cities of China. Acetamiprid (ACE) and imidacloprid (IMI) were the predominated p-NEOs (detection rates: 98%) with the median values at 4.54 and 7.48 ng/g dry weight (dw), respectively. N-demethyl-acetamiprid (N-dm-ACE) was the most important m-NEO with the median value at 0.69 ng/g dw, while other m-NEOs were rarely detected (detection rates: < 15%). Significant correlation between ACE and thiacloprid (THD) was observed (p < 0.01), indicating their probably concurrent applications. ACE was significantly correlated to N-dm-ACE (p < 0.01), implicating the degradation of ACE in indoor environment. The estimated daily intake (EDIing) of NEOs via dust ingestion were far lower than the acceptable daily intake for NEOs. To our knowledge, this study provided a baseline nationwide investigation on the occurrence of NEOs in indoor dust of China.

Engineering Amorphous/Crystalline Structure of Manganese Oxide for Superior Oxygen Catalytic Performance in Rechargeable Zinc-Air Batteries.

Although amorphous materials are popular in oxygen electrocatalysis, their performance requires further improvement to meet the need for rechargeable zinc-air batteries. In this work, an amorphous/crystalline layered manganese oxide (ACMO) was designed, and its unique amorphous/crystalline homogeneous structure activated its oxygen reduction activity with a positive half-wave potential of 0.81 V and oxygen evolution activity with a moderate overpotential of 407 mV at 10 mA cm-2 . Moreover, the amorphous/crystalline structure endowed ACMO with excellent stability. While employed as the air-electrode material for rechargeable zinc-air batteries, ACMO overcame the poor cycling stability of manganese oxide and cycled stably for 1000 cycles (≈17 days) at 10 mA cm-2 . Besides, it delivered a high power density of 159.7 mW cm-2 and a narrow voltage gap of 0.66 V. This work gives an insight into designing oxide materials with amorphous/crystalline structure and feasible guidance for harmonizing electrochemical activity and stability.

Oxygen Defect Engineering of ß-MnO2 Catalysts via Phase Transformation for Selective Catalytic Reduction of NO.

The catalysts for low-temperature selective catalytic reduction of NO with NH3 (NH3 -SCR) are highly desired due to the large demand in industrial furnaces. The characteristic of low-temperature requires the catalyst with rich active sites especially the redox sites. Herein, the authors obtain oxygen defect-rich ß-MnO2 from a crystal phase transformation process during air calcination, by which the as-prepared γ-MnO2 nanosheet and nanorod can be conformally transformed into the corresponding ß-MnO2 . Simultaneously, this transformation accompanies oxygen defects modulation resulted from lattice rearrangement. The most active ß-MnO2 nanosheet with plentiful oxygen defects shows a high efficiency of > 90% NO conversion in an extremely wide operation window of ≈120-350 °C. The detailed characterizations and density functional theory (DFT) calculations reveal that the introduction of oxygen defects enhances the adsorption properties for reactants and decreases the energy barriers of *NH2 formation more than 0.3 eV (≈0.32-0.37 eV), which contributes to a high efficiency of low-temperature SCR activity. The authors finding provides a feasible approach to achieve the oxygen defect engineering and gains insight into manganese-based catalysts for low-temperature NO removal or pre-oxidation.

Nitrogen-Doped Ketjenblack Carbon Supported Co3O4 Nanoparticles as a Synergistic Electrocatalyst for Oxygen Reduction Reaction.

Developing a highly active and cost-effective cathode electrocatalyst with strong stability for oxygen reduction reaction (ORR) is extremely necessary. In this work, we reported a facile synthetic path to prepare a hybrid nanostructure formed of nitrogen-doped Ketjenblack carbon (N-KC) supported Co3O4 nanoparticles (Co3O4/N-KC), which could be used as a promising and stable electrocatalyst for ORR. Compared with the physical mixture of Co3O4 and N-KC and pure N-KC samples, the resulting Co3O4/N-KC nanohybrid afforded remarkably superb ORR activity with a half-wave potential of 0.82 V (vs. reversible hydrogen electrode, RHE) and a limiting current density of 5.70 mA cm-2 in KOH solution (0.1 M). Surprisingly, the Co3O4/N-KC sample possessed a similar electrocatalytic activity but better durability to the 20 wt% Pt/C catalyst. The remarkable ORR activity of the Co3O4/N-KC nanohybrid was mainly due to the strong coupling effect between Co3O4 and N-KC, the N species dopant, high electroconductivity, and the large BET surface area. Our work enlightens the exploitation of advanced Co3O4/carbon hybrid material alternative to the Pt-based electrocatalysts.

C-CoP hollow microporous nanocages based on phosphating regulation: a high-performance bifunctional electrocatalyst for overall water splitting.

Developing economic, effective and stable bifunctional electrocatalysts to achieve sustainable hydrogen production is highly desired. Herein, C-coated CoP hollow microporous nanocages (C-CoP-1/12) are synthesized by calcination of a Prussian blue analog precursor and subsequent phosphorization treatment. Under alkaline condition, the C-CoP-1/12 exhibit splendid electrocatalytic performance with a low overpotential of 173 mV for hydrogen evolution reaction (HER) and 333 mV for oxygen evolution reaction (OER) at a current density of 10 mA cm-2. The C-CoP-1/12 show high electrocatalytic performance for overall water splitting at a low potential of only 1.650 V for the driving current density of 10 mA cm-2, and they exhibit remarkable stability for at least 24 h. The engineering of phosphating is the critical step for the synthesis of pure-phase CoP with hollow nanoarchitecture. Compared with Co2P, CoP possesses lower water dissociation barrier and favorable ΔGH* value according to theoretical calculations, resulting in superior electrocatalytic performance. Such impressive water splitting performance is mainly attributed to the collective effects of metal phosphide with unique electronic structure, the shortened electron transport paths, and the conductive C coating. This strategy is believed to provide a basis for the development of electrode materials with highly efficient electrocatalytic water-splitting capability.

Low-cost superior solid-state symmetric supercapacitors based on hematite nanocrystals.

We present a facile method for the fabrication of hematite nanocrystal-carbon cloth (Fe2O3-CC) composite. Hierarchical manganite is chosen as the sacrificial precursor, that does not contribute to the component of final iron oxide but can be in situ dissolved by the acid produced from the Fe3+ hydrolysis. This method effectively enhances the specific surface area and conductivity of hematite (Fe2O3) by attaching Fe2O3 nanocrystals (around 5 nm) firmly on the surface of carbon fibers. The obtained Fe2O3-CC can be directly used as a binder-free electrode for a supercapacitor. Interestingly, the composite electrode exhibits synergistic electrochemical capacitance (electrochemical double-layer capacitance and pseudo-capacitance). It manifests a very high areal capacitance of 1.66 F cm-2 (1660 F g-1) at 2 mA cm-2 and excellent cycling performance at large current densities (88.6% retention at 30 mA cm-2 after 5000 cycles) in a three-electrode testing system, which is among the best performances reported in the literature. Importantly, when fabricated as a solid-state flexible symmetric supercapacitor it still shows a maximum energy density of 8.74 mW h cm-3 and power density of 253.9 mW cm-3. Additionally, its good flexibility makes it suitable for portable devices.

Multifunctional free-standing membrane from the self-assembly of ultralong MnO2 nanowires.

In this work, we report the preparation of a free-standing membrane with strong mechanical stability and flexibility through a facile vacuum filtration approach. A field-emission scanning electron microscopy image demonstrates that the membrane composed of MnO2 nanowires is 50 nm in width and up to 100 µm long and the nanowires are assembled in parallel into bundles. A possible formation mechanism for the ultralong nanowires and the free-standing membrane has been proposed. Meanwhile, the properties of the membrane could be controlled by incorporating different materials to achieve composite membranes. In order to demonstrate the broad applicability of the MnO2 membrane, we fabricate a variety of composite membranes exhibiting various novel properties including magnetism and reversibly switchable wettability between hydrophilicity and hydrophobicity through various material modification, including CoFe2O4 nanoparticles and organic triethoxy(octyl)silane. Furthermore, the free-standing membrane could also simultaneously be functionalized with two materials, which reveal multiple properties. The synthesis method of a free-standing MnO2 membrane is simple and environmentally friendly, and it is easily scalable for industry. These composite membranes constitute a significant contribution to advanced technology.