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Photo-carrier relaxation in semiconductors determines their photon-conversion efficiency. Impurities have been proven to play an essential role in improving the efficiency and stability of perovskites. We studied the effects of Sr-doping and O-vacancies on the electronic band structure and photoexcited carrier cooling of perovskite-type LaCoO3 using density functional theory and nonadiabatic molecular dynamics methods. We found that the substitution of Sr2+ for La3+ in LaCoO3 leads to a semiconductor–metal transition, while a stoichiometric oxygen vacancy restores semiconductor properties in La1−xSrxCoO3−δ (δ = x/6). In addition, the oxygen vacancy basically changes the electronic band structures, and for visible light with low oxygen vacancy intensity, the photo-electron cooling can be reduced fourfold relative to that of pure LaCoO3. We clarify the functions of impurities, Sr-dopants, and O-vacancies in LaCoO3 and find that the average coupling strength between carriers (electrons/holes) and phonons can be used as a descriptor to characterize carrier relaxation, which is of great value for the further development of practical photo-conversion based on perovskites. [ABSTRACT FROM AUTHOR]

Polymers' controlled pyrolysis is an economical and environmentally friendly solution to prepare activated carbon. However, due to the experimental difficulty in measuring the dependence between microstructure and pyrolysis parameters at high temperatures, the unknown pyrolysis mechanism hinders access to the target products with desirable morphologies and performances. In this study, we investigate the pyrolysis process of polystyrene (PS) under different heating rates and temperatures employing reactive molecular dynamics (ReaxFF-MD) simulations. A clear profile of the generation of pyrolysis products determined by the temperature and heating rate is constructed. It is found that the heating rate affects the type and amount of pyrolysis intermediates and their timing, and that low-rate heating helps yield more diverse pyrolysis intermediates. While the temperature affects the pyrolytic structure of the final equilibrium products, either too low or too high a target temperature is detrimental to generating large areas of the graphitized structure. The reduced time plots (RTPs) with simulation results predict a PS pyrolytic activation energy of 159.74 kJ/mol. The established theoretical evolution process matches experiments well, thus, contributing to preparing target activated carbons by referring to the regulatory mechanism of pyrolytic microstructure. [ABSTRACT FROM AUTHOR]

The preparation of nitrogen-containing porous carbon (NCPC) materials by controlled carbonization is an exciting topic due to their high surface area and good conductivity for use in the fields of electrochemical energy storage and conversion. However, the poor controllability of amorphous porous carbon prepared by carbonization has always been a tough problem due to the unclear carbonation mechanism, which thus makes it hard to reveal the microstructure–performance relationship. To address this, here, we comprehensively employed reactive molecular dynamics (ReaxFF-MD) simulations and first-principles calculations, together with machine learning technologies, to clarify the carbonation process of polypyrrole, including the deprotonation and formation of pore structures with temperature, as well as the relationship between microstructure, conductance, and pore size. This work constructed ring expressions for PPy thermal conversion at the atomic level. It revealed the structural factors that determine the conductivity and pore size of carbonized products. More significantly, physically interpretable machine learning models were determined to quantitatively express structure factors and performance structure–activity relationships. Our study also confirmed that deprotonation preferentially occurred by desorbing the dihydrogen atom on nitrogen atoms during the carbonization of PPy. This theoretical work clearly reproduces the microstructure evolution of polypyrrole on an atomic scale that is hard to do via experimentation, thus paving a new way to the design and development of nitrogen-containing porous carbon materials with controllable morphology and performance. [ABSTRACT FROM AUTHOR]

The technology and functions of data fusion and image teaching are constantly improving with the development of society and are gradually produced in life in order to adapt to the progress of science and technology. Data fusion technology refers to the information processing technology that uses computer to automatically analyze and synthesize several observation information obtained in time series under certain criteria to complete the required decision-making and evaluation tasks. In this paper, the traditional teaching mode on students' learning and other aspects of help is not very obvious, and video teaching method can not only increase students' interest in learning, but also help their learning is very huge. Teaching video is to make the knowledge, skills, and other content that teachers want to impart to students into video form to assist modern multimedia teaching. In this paper, two classes with the same number and similar average test scores were selected as the experimental objects. The test results are evaluated by f-s-o algorithm, f-s-o matrix, variance proportion method, and teaching evaluation, so as to get more accurate results. In the experiment, two classes with 30 students were selected, and different teaching methods were adopted for the two classes. One class adopted the traditional teaching mode, and the other class used the video teaching method. During the 4-month experiment, there was no significant difference in test scores and comprehension between the two classes in the first month. The ratio of the two classes was 5 : 3 in the second month, 10 : 5 in the third month, and 20 : 7 in the fourth month. Through the comparative evaluation of the test results of four months, the experimental results show that the video teaching method can not only mobilize the enthusiasm of students but also plays a very important role in promoting students' performance. [ABSTRACT FROM AUTHOR]

It has been a hot research topic to look for inexpensive alternative oxygen evolution reaction (OER) catalysts to replace noble metal-based materials due to their scarcity. Transition metals are ideal candidates because of their high abundance, impressive activities, and easy accessibility. However, a facile method leading to improved performance and stability is still needed. Herein, a highly efficient carbon-encapsulated bimetal catalyst derived from Ni-based metal-organic-frameworks (MOF) was successfully prepared through the low-temperature (350 ℃) pyrolysis of Prussian blue analogue (PBA) precursors under H 2 /Ar atmosphere. Cube-structured PBA as template and precursor，parameters during the pyrolysis process including temperature and calcination atmosphere can be tuned to control the structure and properties of the catalysts. Benefiting from the porous three-dimensional (3D) cubic structure and abundant defect-rich amorphous N-doped carbon shell, Ni 3 Fe@NC-350 exhibits excellent OER activity. The as-prepared catalysts exhibited excellent catalytic performance for OER in 1.0 M KOH with an overpotential of 237 mV to achieve 10 mA cm−2. More importantly, the presented catalyst has an extremely good durability. • A simple low-temperature annealing method was developed to produce alloy encapsulated with N-doping carbon. • The NiFe PBA was employed as nitrogen and carbon source. • The increased activity of OER is due to the synergy of Ni 3 Fe alloy and N-doped carbon layer. • Theoretical calculations revealed that the synergistic effect of NiFe alloy nanoparticles and N-doped carbon layer. [ABSTRACT FROM AUTHOR]