In situ visualizing reveals potential drive of lattice expansion on defective support toward efficient removal of nitrogen oxides.

As a sustainable and promising approach of removing of nitrogen oxides (NOx), catalytic reduction of NOx with H2 is highly desirable with a precise understanding to the structure-activity relationship of supported catalysts. In particular, the dynamic evolution of support at microscopic scale may play a critical role in heterogeneous catalysis, however, identifying the in situ structural change of support under working condition with atomic precision and revealing its role in catalysis is still a grand challenge. Herein, we visually capture the surface lattice expansion of WO3-x support in Pt-WO3-x catalyst induced by NO in the exemplified reduction of NO with H2 using in situ transmission electron microscopy and first reveal its important role in enhancing catalysis. We find that NO can adsorb on the oxygen vacancy sites of WO3-x and favorably induce the reversible stretching of W-O-W bonds during the reaction, which can reduce the adsorption energy of NO on Pt4 centers and the energy barrier of the rate-determining step. The comprehensive studies reveal that lattice expansion of WO3-x support can tune the catalytic performance of Pt-WO3-x catalyst, leading to 20% catalytic activity enhancement for the exemplified reduction of NO with H2. This work reveals that the lattice expansion of defective support can tune and optimize the catalytic performance at the atomic scale.

In situ formation of cocatalytic sites boosts single-atom catalysts for nitrogen oxide reduction.

Nitrogen oxide (NOx) pollution presents a severe threat to the environment and human health. Catalytic reduction of NOx with H2 using single-atom catalysts poses considerable potential in the remediation of air pollution; however, the unfavorable process of H2 dissociation limits its practical application. Herein, we report that the in situ formation of PtTi cocatalytic sites (which are stabilized by Pt-Ti bonds) over Pt1/TiO2 significantly increases NOx conversion by reducing the energy barrier of H2 activation. We demonstrate that two H atoms of H2 molecule are absorbed by adjacent Pt atoms in Pt-O and Pt-Ti, respectively, which can promote the cleave of H-H bonds. Besides, PtTi sites facilitate the adsorption of NO molecules and further lower the activation barrier of the whole de-NOx reaction. Extending the concept to Pt1/Nb2O5 and Pd1/TiO2 systems also sees enhanced catalytic activities, demonstrating that engineering the cocatalytic sites can be a general strategy for the design of high-efficiency catalysts that can benefit environmental sustainability.

Enhanced localized dipole of Pt-Au single-site catalyst for solar water splitting.

Solar water splitting is regarded as holding great potential for clean fuels production. However, the efficiency of charge separation/transfer of photocatalysts is still too low for industrial application. This paper describes the synthesis of a Pt-Au binary single-site loaded g-C3N4 nanosheet photocatalyst inspired by the concept of the dipole. The existent larger charge imbalance greatly enhanced the localized molecular dipoles over adjacent Pt-Au sites in contrast to the unary counterparts. The superposition of molecular dipoles then further strengthened the internal electric field and thus promoted the charge transportation dynamics. In the modeling photocatalytic hydrogen evolution, the optimal Pt-Au binary site photocatalysts (0.25% loading) showed 4.9- and 2.3-fold enhancement of performance compared with their Pt and Au single-site counterparts, respectively. In addition, the reaction barrier over the Pt-Au binary sites was lowered, promoting the hydrogen evolution process. This work offers a valuable strategy for improving photocatalytic charge transportation dynamics by constructing polynary single sites.

Wood-Derived High-Mass-Loading MnO2 Composite Carbon Electrode Enabling High Energy Density and High-Rate Supercapacitor.

The simple design of a high-energy-density device with high-mass-loading electrode has attracted much attention but is challenging. Manganese oxide (MnO2 ) with its low cost and excellent electrochemical performance shows high potential for practical application in this regard. Hence, the high-mass-loading of the MnO2 electrode with wood-derived carbon (WC) as the current collector is reported through a convenient hydrothermal reaction for high-energy-density devices. Benefiting from the high-mass-loading of the MnO2 electrode (WC@MnO2 -20, ≈14.1 mg cm-2 ) and abundant active sites on the surface of the WC hierarchically porous structure, the WC@MnO2 -20 electrode shows remarkable high-rate performance of areal/specific capacitance ≈1.56 F cm-2 /45 F g-1 , compared to the WC electrode even at the high density of 20 mA cm-2 . Furthermore, the obtained symmetric supercapacitor exhibits high areal/specific capacitances of 3.62 F cm-2 and 87 F g-1 at 1.0 mA cm-2 and high energy densities of 0.502 mWh cm-2 /12.2 Wh kg-1 with capacitance retention of 75.2% after 10 000 long-term cycles at 20 mA cm-2 . This result sheds light on a feasible design strategy for high-energy-density supercapacitors with the appropriate mass loading of active materials and low-tortuosity structural design while also encouraging further investigation into electrochemical storage.

The Role of Alkali Metal in α-MnO2 Catalyzed Ammonia-Selective Catalysis.

The unexpected phenomenon and mechanism of the alkali metal involved NH3 selective catalysis are reported. Incorporation of K+ (4.22 wt %) in the tunnels of α-MnO2 greatly improved its activity at low temperature (50-200 °C, 100 % conversion of NOx vs. 50.6 % conversion over pristine α-MnO2 at 150 °C). Experiment and theory demonstrated the atomic role of incorporated K+ in α-MnO2 . Results showed that K+ in the tunnels could form a stable coordination with eight nearby O sp 3 atoms. The columbic interaction between the trapped K+ and O atoms can rearrange the charge population of nearby Mn and O atoms, thus making the topmost five-coordinated unsaturated Mn cations (Mn5c , the Lewis acid sites) more positive. Therefore, the more positively charged Mn5c can better chemically adsorb and activate the NH3 molecules compared with its pristine counterpart, which is crucial for subsequent reactions.

Performance of Full-Component Coal Gasification Fine Slag: High-Value Utilization as Reinforcing Material in Styrene-Butadiene Rubber (ESBR) for Replacing Carbon Black.

Ultrafine, highly active coal gasification slag (HCGS) was produced via a sustainable, green dry-ball-milling method. Coal gasification fine slag (CGS), a potential environmental pollutant, was used as a new source of rubber filler without pre-treatment, enabling waste utilisation. HCGS was added to styrene-butadiene rubber (ESBR) composites, and the effects of HCGS and the filler content on the mechanical and thermal stabilities of SBR were evaluated. The procedure conforms to important green metrics, requiring no solvent or additional reagent, or solvent-assistance for product collection. HCGS reduced the scorch time (t10) and curing time (t90) of the filled ESBR composites relative to those of pure SBR and improved the mechanical parameters. The tensile strength at 50 phr reached 10.91 MPa, and the tear strength at 90 phr reached 64.92 kN/m, corresponding to 9.4- and 3.92-fold increases relative to that of SBR filled with HCGS, respectively. HCGS exerted a reinforcing effect on ESBR, comparable to that of commercial carbon black (CB) N330. HCGS improves the binding between rubber molecules and filler particles and captures the rubber chain, thereby limiting its movement. HCGS is potentially applicable as a CB substitute in the rubber industry, with environmental and economic benefits in the disposal of CGS.

Insight into the effect of chemical structure for microbial lignite methanation.

The chemical structure of lignite plays a fundamental role in microbial degradation, which can be altered to increase gas production. In this study, the structural changes in lignite were analyzed by conducting pretreatment and biomethane gas production experiments using crushing and ball milling processes, respectively. The results revealed that different particle size ranges of lignite considerably influence gas production. The maximum methane yield under both treatments corresponded to a particle size range of 400-500 mesh. The gas production after ball milling was higher than that after crushing, irrespective of particle size. Compared with lignite subjected to crushing, that subjected to ball milling exhibited more oxygen-containing functional groups, less coalification, more disordered structures, and small aromatic ring structures, demonstrating more unstable properties, which are typically favorable to microbial flora for the utilization and degradation of lignite. Additionally, a symbiotic microbial community comprising multiple species was established during the microbial degradation of lignite into biogas. This study provides new insights and a strong scientific foundation for further research on microbial lignite methanation.

Enhanced hydrophobic ZSM-5 with high capacity for toluene capture under high-humidity conditions.

Industrial volatile organic compounds (VOCs) have the characteristics of large displacement and high humidity. The problem of water resistance of the adsorbent in treating VOCs by adsorption method under high humidity conditions needs to be solved urgently. Herein, methyl triethoxysilane (CH3Si(C2H5O)3) and methyl trimethoxysilane (CH3Si(CH3O)3) are used for hydrophobic modification of ZSM-5, and its adsorption properties for toluene are studied under high-humidity conditions. Fourier infrared spectroscopy and X-ray photoelectron spectroscopy indicate that the hydrophobic groups -CH3 and -CH2- are successfully grafted onto the surface of the ZSM-5. The adsorption-desorption results of toluene show that the hydrophobicity of the modified ZSM-5 is remarkably improved, and the adsorption capacity for toluene is almost 6.5 times higher than that of original ZSM-5 at 80 % relative humidity. The mechanism of surface hydrophobicity modification of ZSM-5 was further investigated and found that the silicone hydroxyl group on the surface of the material reacted with the modifier to graft the hydrophobic group onto the surface of the material, which improved the hydrophobic property of the material. Moreover, the universality of the hydrophobic modification method has been proved feasible in commercial ZSM-5. Therefore, this work provides an important theory and reference for improving the hydrophobic properties of ZSM-5 molecular sieve.

Mechanistic insights into the chemical structural changes of lignite on potential formation of the polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) generated during lignite combustion and gasification are highly carcinogenic, teratogenic, and mutagenic. Leveraging solvent extraction without damaging the macromolecular structure of lignite could help better understand the chemical structure and further clarify the possible source of PAHs, and the possibility of their elimination, thereby improving lignite utilization efficiency. In this study, methanol, ethanol, dichloromethane, and n-hexane were used to extract the feedstock at room temperature, and the constituents of the extracts were analyzed using GC-MS. The study showed that poly-condensed aromatic constituents were present in relatively high percentage in the extracts, due to the polarity effect of solvents, and could have a noticeable impact on the generation of PAHs. The aromatic hydrocarbons content accounts for nearly 70% of the total, which is about 10% higher than that of aliphatic hydrocarbons, and mainly exist in the form of 2 and 3 rings. Furthermore, FTIR, XRD and Raman were used to evaluate the macromolecular structural characteristics and the relevant information of the lignite bonds. The study demonstrated that the rupture of weak C-O or C-C covalent bonds promoted a more aromatic product, as strongly cross-linked networks of polycyclic aromatic components remained. The potential generation of PAHs was comprehensively ascertained by evaluating the extracts obtained at room temperature and products of combustion test， which can provide more information on PAHs pollutants.

[Effect of cotton-moxibustion on chronic eczema and quality of life].

OBJECTIVE: To compare the therapeutic effect between cotton-moxibustion and compound flumetasone ointment, and observe the effect on quality of life in patients with chronic eczema. METHODS: A total of 66 patients with chronic eczema were randomized into an observation group (33 cases, 2 cases dropped off) and a control group (33 cases, 2 cases dropped off). In the observation group, cotton-moxibustion was adopted on target skin lesion, once a day, 3 cones a time. In the control group, external application of compound flumetasone ointment was given twice a day. The treatment for 3 weeks was required in the both groups. Before treatment and 1,2,3 weeks into treatment, scores of visual analogue scale (VAS), eczema area and severity index (EASI) and dermatology life quality index (DLQI) were observed, and the recurrence rate was evaluated in the follow-up one month after treatment. RESULTS: Compared before treatment, the VAS scores of 1,2,3 weeks into treatment, the EASI and DLQI scores of 2,3 weeks into treatment were decreased in the both groups (P<0.05), and those in the observation group were lower than the control group (P<0.05). The follow-up recurrence rate in the observation group were lower than the control group (P<0.05). CONCLUSION: Cotton-moxibustion can effectively improve the pruritus symptom, skin lesion and quality of life in the patients with chronic eczema, the therapeutic effect is superior to the external application of compound flumetasone ointment.