Modulating Electronic Structures of Iron Clusters through Orbital Rehybridization by Adjacent Single Copper Sites for Efficient Oxygen Reduction.

The atom-cluster interaction has recently been exploited as an effective way to increase the performance of metal-nitrogen-carbon catalysts for oxygen reduction reaction (ORR). However, the rational design of such catalysts and understanding their structure-property correlations remain a great challenge. Herein, we demonstrate that the introduction of adjacent metal (M)-N4 single atoms (SAs) could significantly improve the ORR performance of a well-screened Fe atomic cluster (AC) catalyst by combining density functional theory (DFT) calculations and experimental analysis. The DFT studies suggest that the Cu-N4 SAs act as a modulator to assist the O2 adsorption and cleavage of O-O bond on the Fe AC active center, as well as optimize the release of OH* intermediates to accelerate the whole ORR kinetic. The depositing of Fe AC with Cu-N4 SAs on nitrogen doped mesoporous carbon nanosheet are then constructed through a universal interfacial monomicelles assembly strategy. Consistent with theoretical predictions, the resultant catalyst exhibits an outstanding ORR performance with a half-wave potential of 0.92 eV in alkali and 0.80 eV in acid, as well as a high power density of 214.8 mW cm-2 in zinc air battery. This work provides a novel strategy for precisely tuning the atomically dispersed poly-metallic centers for electrocatalysis.

Design of a Fuzzy Algorithm-Based Evaluation System for the Effectiveness of International Online Chinese Listening and Speaking Teaching.

With the increasing popularity of online foreign language teaching and learning practice, learners and teachers have developed a high demand for evaluation of teaching effectiveness. When we focus discussion on international Chinese teaching, which has been developed for a relatively short time and not experienced enough, online teaching effectiveness evaluation has become an important obstacle to the development of teaching. This paper introduces a hybrid technique based on fuzzy evaluation method, for determining and suggesting possible types of errors in international Chinese online listening and speaking instruction and giving suggestions for improvement. The system can help learners to identify and determine the types of errors in Chinese listening and speaking learning in a timely manner and make a more objective and comprehensive evaluation of learning performance; at the same time, it helps teachers to trace the effectiveness of teaching design and implementation in a targeted manner and make corresponding scientific decisions. This hybrid technology combines existing language teaching evaluation models, takes advantage of data from online education, and creates corresponding criteria through machine learning fuzzy algorithms and large data sample training, combined with the theory of effective teaching evaluation, which is beneficial for all participants of online Chinese listening and speaking teaching to improve their learning effectiveness.

A Universal Single-Atom Coating Strategy Based on Tannic Acid Chemistry for Multifunctional Heterogeneous Catalysis.

Here, we report a universal single-atom coating (SAC) strategy by taking advantage of the rich chemistry of tannic acid (TA). TA units not only self-assemble into a cross-linked porous polyphenolic framework, but also can grip on different substates via multiple binding modes. Benefiting from the diverse chelating ability of TA, a series of mono-, and bi-metallic SACs can be formed on substrates of different materials (e. g., carbon, SiO2 , TiO2 , MoS2 ), dimensions (0D-3D) and sizes (50 nm-5 cm). By contrast, uniform SAC cannot be achieved using common approaches such as pyrolysis of metal-dopamine complexes or metal-organic frameworks. As a proof-of-concept demonstration, two Co SACs immobilized on graphene and TiO2 were prepared. The former one shows six-fold higher mass activity than Pt/C toward oxygen reduction. The latter one displays outstanding photocatalytic activity owing to the high activity of the single atoms and the formation of the single-atom coating-TiO2 heterojunction.

Facile preparation of robust superhydrophobic cotton fabric for ultrafast removal of oil from contaminated waters.

A new class of robust superhydrophobic cotton fabric was prepared by chemically grafting method for removing oil from contaminated waters. Furthermore, the mechanical, chemical, and thermal durability of superhydrophobic cotton fabric was evaluated in detail. The superhydrophobic cotton fabric did not only showed excellent separation efficiency (ca.100%) and ultrafast separation rate (ca. 13,600 L/h m2) but also exhibited excellent durability. Especially, the oil/water separation rate was almost 10 times than that reported in previous works. The work provides a new method to design and large-scale prepare oil/water separation materials with high performance for industrial use.

Robust Superhydrophobic Surface Based on Multiple Hybrid Coatings for Application in Corrosion Protection.

A new class of superhydrophobic surface based on multiple hybrid coatings is proposed and prepared to improve mechanical and reproduction stability. It does not only show a large water contact angle (ca. 174.5°) but also a slight decrease (ca. 6.4%) of water contact angle after 100 mechanical abrasion cycles. Furthermore, the water contact angle changes slightly (relative standard deviation, 0.14%) for the three superhydrophobic surfaces prepared with the same procedure. The application of superhydrophobic multiple hybrid coatings in corrosion protection is further investigated by the Tafel polarization curves and electrochemical impedance spectroscopy. The superhydrophobic multiple hybrid coatings showed lower corrosion current (1.4 × 10-11 A/cm2), lower corrosion rate (ca. 1.6 × 10-7 mm/year), and larger polarization resistance (7.9 × 104 MΩ cm2) in 3.5 wt % NaCl aqueous solution compared to other superhydrophobic coatings reported in previous works. This work not only confirms the formation of robust superhydrophobic surface for real application in corrosion protection but also provides a new model of superhydrophobic surface based on multiple hybrid coatings with high mechanical, chemical, and reproduction stability for various applications.

Descent algorithms on oblique manifold for source-adaptive ICA contrast.

A Riemannian manifold optimization strategy is proposed to facilitate the relaxation of the orthonormality constraint in a more natural way in the course of performing independent component analysis (ICA) that employs a mutual information-based source-adaptive contrast function. Despite the extensive development of manifold techniques catering to the orthonormality constraint, only a limited number of works have been dedicated to oblique manifold (OB) algorithms to intrinsically handle the normality constraint, which has been empirically shown to be superior to other Riemannian and Euclidean approaches. Imposing the normality constraint implicitly, in line with the ICA definition, essentially guarantees a substantial improvement in the solution accuracy, by way of increased degrees of freedom while searching for an optimal unmixing ICA matrix, in contrast with the orthonormality constraint. Designs of the steepest descent, conjugate gradient with Hager-Zhang or a hybrid update parameter, quasi-Newton, and cost-effective quasi-Newton methods intended for OB are presented in this paper. Their performance is validated using natural images and systematically compared with the popular state-of-the-art approaches in order to assess the performance effects of the choice of algorithm and the use of a Riemannian rather than Euclidean framework. We surmount the computational challenge associated with the direct estimation of the source densities using the improved fast Gauss transform in the evaluation of the contrast function and its gradient. The proposed OB schemes may find applications in the offline image/signal analysis, wherein, on one hand, the computational overhead can be tolerated, and, on the other, the solution quality holds paramount interest.