We successfully synthesized a porous carbon material with abundant hexagonal boron nitride (h-BN) dispersed on a carbon matrix (p-BN-C) as efficient electrocatalysts for two-electron oxygen reduction reaction ( 2e− ORR) to produce hydrogen peroxide ( H2O2). This catalyst was fabricated via ball-milling-assisted h-BN exfoliation and subsequent growth of carbon structure. In alkaline solutions, the h-BN/carbon heterostructure exhibited superior electrocatalytic activity for H2O2 generation measured by a rotating ring-disk electrode (RRDE), with a remarkable selectivity of up to 90–97% in the potential range of 0.3–0.6 V vs reversible hydrogen electrode (RHE), superior to most of the reported carbon-based electrocatalysts. Density functional theory (DFT) simulations indicated that the B atoms at the h-BN heterostructure interface were crucial active sites. These results underscore the remarkable catalytic activity of heterostructure and provide a novel approach for tailoring carbon-based catalysts, enhancing the selectivity and activity in the production of H2O2 through heterostructure engineering.
Chlorine is a crucial radionuclide that must be removed in irradiated nuclear graphite. Understanding the interaction between chlorine and graphene-based materials is essential for studying the removal process of 36Cl from irradiated nuclear graphite. In this study, first-principle density functional theory (DFT) was utilized to investigate the adsorption characteristic of chlorine on the original and reconstructed edges of graphene-based materials. Based on the calculation of adsorption energy of the structures after each step of adsorption, the most energetically favorable adsorption routes at four types of edge were determined: Along the armchair edge and reconstructed zigzag edge, the following adatoms would be adsorbed to compensate the distortion induced by the previously adsorbed atom. Meanwhile at the original zigzag edge, chlorine atoms would be adsorbed alternatively along the edge to minimize the repulsion between two adjacent chlorine atoms. The chemical nature of the bonds formed as a result of adsorption was elucidated through an examination of the density of states (DOS) for the two adsorbed chlorine atoms and the carbon atoms attached. Furthermore, to assess the relative stability of the adsorption structures, formation energy of all energetically favorable structures following adsorption was computed. Consequently, the predominant adsorption structure was identified as the reconstructed armchair edge with two chlorine atoms adsorbed. The desorption process of 36Cl2 from the predominant structure following adsorption was simulated, revealing an energy barrier of 1.14 V for desorption. Comparison with experimental results suggests that the chlorine removed from reconstructed armchair edges significantly contributes to the low-temperature removal stage of 36Cl from irradiated nuclear graphite.
Artificial photosynthesis harnesses clean and sustainable solar power to catalyze the conversion of CO2 and H2O molecules into valuable chemicals and O2. This sustainable approach combines energy conversion with environmental pollution control. Non-oxide photocatalysts with broad visible-light absorption and suitable band structures, hold immense potential for CO2 conversion. Nevertheless, they still face numerous challenges in practical applications, particularly in CO2 conversion with H2O. Surface modification and functionalization play the significant role in improving the activity of non-oxide photocatalysts. Multifarious strategies, such as cocatalyst loading, surface regulation, doping engineering, and heterostructure construction, have been explored to optimize light harvesting, bandgap driving force, electron–hole pairs separation/transfer, CO2 adsorption, activation, and catalysis processes. This review summarizes recent progress in surface modification strategies for non-oxide photocatalysts and discusses their enhancement mechanisms for efficient CO2 conversion. These insights are expected to guide the design of high-performance non-oxide photocatalyst systems.
Pyrolysis of methane is a carbon-economic method to obtain valuable carbon materials and COx- free H2, under the carbon peaking and carbon neutrality goals. In this work, we propose a methane pyrolysis process to produce graphite and H2 using bubble column reactor containing NiO/Al2O3 and NaCl–KCl (molten salt). The process was optimized by the different amounts of NaCl–KCl, the CH4/ Ar ratio and temperature, indicating that the CH4 conversation rate could reach 92% at 900 °C. Meanwhile, we found that the addition of molten salt could obtain pure carbon materials, even if the conversation rate of CH4 decreases. The analysis of the carbon products revealed that graphite could be obtained.
Exploring highly efficient, and low-cost oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts is extremely vital for the commercial application of advanced energy storage and conversion devices. Herein, a series of graphene-like C2N supported TMx@C2N, (TM = Fe, Co, Ni, and Cu, x = 1, 2) single- and dual-atom catalysts are designed. Their catalytic performance is systematically evaluated by means of spin-polarized density functional theory (DFT) computations coupled with hydrogen electrode model. Regulating metal atom and pairs can widely tune the catalytic performance. The most promising ORR/OER bifunctional activity can be realized on Cu2@ C2N with lowest overpotential of 0.46 and 0.38 V for ORR and OER, respectively. Ni2@ C2N and Ni@C2N can also exhibit good bifunctional activity through effectively balancing the adsorption strength of intermediates. The correlation of reaction overpotential with adsorption free energy is well established to track the activity and reveal the activity origin, indicating that catalytic activity is intrinsically governed by the adsorption strength of reaction intermediates. The key to achieve high catalytic activity is to effectively balance the adsorption of multiple reactive intermediates by means of the synergetic effect of suitably screened bimetal atoms. Our results also demonstrate that lattice strain can effectively regulate the adsorption free energies of reaction intermediates, regarding it as an efficient strategy to tune ORR/OER activity. This study could provide a significant guidance for the discovery and design of highly active noble-metal-free carbon-based ORR/OER catalysts.
pH plays a pivotal role in influencing various aspects of proton-coupled electron transfer (PCET) reactions in electrochemical systems. These reactions are affected by pH in terms of mass transport, electrochemical double layer (EDL) structure, and surface adsorption energy, all of which impact the overall electrochemical processes. This review article aims to provide a comprehensive understanding of the research progress made in elucidating the effects of pH on different electrochemical reactions, the hydrogen evolution reaction/hydrogen oxidation reaction (HER/HOR), oxygen reduction reaction/oxygen evolution reaction (ORR/OER), and carbon dioxide reduction reaction ( CO2RR). To embark on this endeavor, we have conducted a bibliometric analysis to clearly outline of the research trends and advancements in the field concerning the pH effects. Subsequently, we present a systematic overview of the mechanisms governing these reactions, with a special focus on pH’s influence on both the proton and electron aspects. We conclude by discussing the current challenges in this area and suggesting future research avenues that could further our understanding of pH's role in electrochemical reactions.
2018 평창 동계 올림픽에서 중국과 한국 간의 사신 문화 논쟁을 계기 로, 비교 신화학을 통해 중국, 일본, 한국의 동아시아 사신 문화를 살펴 본 연구이다. 본 연구는 고고학, 인류학, 문학, 역사, 심리학을 결합한 학 제간 접근을 강조하며, 문헌 분석, 무덤 벽화 비교, 풍수지리 실천을 통 해 이들 문화에서 사신의 묘사와 의미의 공통점과 차이점을 밝혀냈다. 연구는 사신 문화 공동체를 구축하는 것이 넓은 의미의 동아시아 문화 공동체로 나아가는 단계로서의 실행 가능성과 필요성을 제안하며, 이에 대한 이론적 지지를 제공하였다. 향후 연구는 동아시아 문화의 영향을 받은 다른 지역으로 확장하고, 사신 상징의 현대적 응용을 탐구하며, 이 문화 유산의 보존 및 전파를 위한 디지털 도구를 개발하는 것을 목표로 한다.
이 연구는 20세기 말 이후 중국과 남한의 올림픽 포스터 디자인에서 두드러진 특징과 미묘함을 분석하고 비교합니다. 시각적 표현, 문화적 함 의, 그리고 그들의 사회-역사적 맥락 내의 의사소통 전략을 탐구합니다. 이 연구는 양국이 어떻게 전통적 요소와 현대적 디자인을 독특하게 혼합 하여 국가 정신과 문화적 정체성을 표현하며, 대중의 인식과 감정에 영 향을 주는지를 밝혀냅니다. 또한, 이러한 디자인 뒤에 있는 사회-정치적 동기를 논의하며 미래의 추세를 예상합니다. 이 분석은 중국과 한국의 포스터 디자인의 독특한 가치와 문화 간 의사소통에서의 역할에 대한 새 로운 통찰을 제공합니다.
본 연구는 COVID-19 중∙후 과정에서 나타난 중국 4세 유아의 신체 발달, 정서발달의 실태 현황을 파악하여 이를 토대로 정책적 제안을 하 고자 한다. 이를 위해 동영시와 빈저우시에 거주하는 중국 4세 유아의 학부모 1,040명을 통해 설문지를 수집하였으며 수집된 설문지는 SPSS 25.0을 이용하여 분석하였다. 이를 통해 국가및 지역사회의 유아교육 정 책 입안자, 유아교육 기관의 교직원, 학부모 등 유아 발달에 관한 정책 방안 및 실제적인 지침을 수립하는데 필요한 기초정보를 제공하고자 한 다. 또한 유아의 신체발달, 정서발달에 관한 다양한 프로그램을 개발하는 데에도 도움을 주고자 한다.
In this paper, iron ore tailings (IOT) were separated from the tailings field and used to prepare cement stabilized macadam (CSM) with porous basalt aggregate. First, the basic properties of the raw materials were studied. Porous basalt was replaced by IOT at ratios of 0, 20 %, 40 %, 60 %, 80 %, and 100 % as fine aggregate to prepare CSM, and the effects of different cement dosage (4 %, 5 %, 6 %) on CSM performance were also investigated. CSM’s durability and mechanical performance with ages of 7 d, 28 d, and 90 d were studied with the unconfined compression strength test, splitting tensile strength test, compressive modulus test and freeze-thaw test, respectively. The changes in Ca2+ content in CSM of different ages and different IOT ratios were analyzed by the ethylene diamine tetraacetic acid (EDTA) titration method, and the micro-morphology of CSM with different ages and different IOT replaced ratio were observed by scanning electron microscopy (SEM). It was found that with the same cement dosage, the strengths of the IOT-replaced CSM were weaker than that of the porous basalt aggregate at early stage, and the strength was highest at the replaced ratio of 60 %. With a cement dosage of 4 %, the unconfined compressive strength of CSM without IOT was increased by 6.78 % at ages from 28 d to 90 d, while the splitting tensile strength increased by 7.89 %. However, once the IOT replaced ratio reached 100 %, the values increased by about 76.24 % and 17.78 %, which was better than 0 % IOT. The CSM-IOT performed better than the porous basalt CSM at 90 d age. This means IOT can replace porous basalt fine aggregate as a pavement base.
In this study, four different samples of Se60Ge40-xBix chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E1 and E2). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(Eext) and localized states N(Eloc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 1014 to 4.2 × 1012 (ev-1 cm-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 1021 to 5.86 × 1021 (ev-1 cm-3), indicating a reduction in the mullet’s randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.
Electric-propulsion systems for ships, also known as electric propulsion devices, represent the current direction of development for maritime power. Issues concerning the environment and fuel economy have compelled the maritime transport sector to seek solutions that reduce emissions and improve fuel efficiency. In this process, power electronics technology plays a significant role in the propulsion systems of ships. Selecting an efficient battery system is of great importance for enhancing the cruising range of yachts and minimizing environmental impact. The battery model is crucial for revealing the working principles of batteries, and it is extremely critical for the application and development of battery technology. The Battery Management System (BMS) serves a crucial regulatory function, optimizing both the safety and performance of battery cells. Central to its operation is the precise estimation of the battery's State of Charge (SOC), a process dependent on an exacting battery model. This system not only enhances longevity and reliability but also ensures that energy storage solutions meet high standards of efficacy. This study focused on testing the impedance characteristics of lithium-sulfur batteries (LSB) at various SOC points and establishing first- and second-order RC equivalent circuit models. The model parameters were identified through experimental data. Subsequently, a simulation platform was constructed using MATLAB/Simulink to simulate the behavior of LSB under a constant current discharge condition. The simulation results showed that the second-order RC model had significantly lower errors than the first-order model, demonstrating higher accuracy. These achievements can provide technical support for the research of energy storage systems in the green aviation and maritime industries.
CO2 photocatalytic reduction is a carbon–neutral renewable energy technology. However, this technology is restricted by the low utilization of photocatalytic electrons. Therefore, to improve the separation efficiency of photogenerated carriers and enhance the performance of CO2 photocatalytic reduction. In this paper, g-C3N4/Pd composite with Schottky junction was synthesized by using g-C3N4, a two-dimensional material with unique interfacial effect, as the substrate material in combination with the co-catalyst Pd. The composite of Pd and g-C3N4 was tested to have a strong localized surface plasmon resonance effect (LSPR), which decreased the reaction barriers and improved the electron utilization. The combination of reduced graphene oxide (rGO) created a π–π conjugation effect at the g-C3N4 interface, which shortened the electron migration path and further improved the thermal electron transfer and utilization efficiency. The results show that the g-C3N4/ rGO/Pd (CRP) exhibits the best performance for photocatalytic reduction of CO2, with the yields of 13.57 μmol g− 1 and 2.73 μmol g− 1 for CO and CH4, respectively. Using the in situ infrared test to elucidate the intermediates and the mechanism of g-C3N4/rGO/Pd (CRP) photocatalytic CO2 reduction. This paper provides a new insight into the interface design of photocatalytic materials and the application of co-catalysts.
For the regeneration of diesel particulate filters (DPF) using non-thermal plasma (NTP), both cost-effectiveness and regeneration efficiency should be raised. This study compared and contrasted the physicochemical characteristics of carbon black and engine particulate matter (PM). After carbon black was put into the DPF, an experimental setup for the oxidation of PM using NTP was created. The findings showed that carbon black and PM samples had comparable oxidation traits, micronanostructures, and C/O elemental ratios. O3, the main active species in NTP, was susceptible to heat breakdown, and the rate of decomposition of O3 increases with increasing temperature. The removal effectiveness of carbon black first improved and subsequently declined with an increase in the NTP injection flow rate during offline DPF regeneration using NTP at room temperature. A relatively high carbon black removal efficiency of 85.1% was achieved at an NTP injection flow rate of 30 L/min.
Copper-coated carbon fibers have excellent conductivity and mechanical properties, making them a promising new lightweight functional material. One of the main challenges to their development is the poor affinity between carbon fiber and metals. This paper selects different carbon fibers for copper electroplating experiments to study the effect of carbon fiber properties on the interface bonding performance between the copper plating layer and carbon fibers. It has been found that the interfacial bonding performance between copper and carbon fiber is related to the degree of graphitization of carbon fiber. The lower the degree of graphitization of carbon fiber, the smaller the proportion of carbon atoms with sp2 hybrid structure in carbon fiber, the stronger the interfacial bonding ability between carbon fiber and copper coating. Therefore, carbon fiber with lower graphitization degree is conducive to reducing the falling off rate of copper coating and improving the quality of copper coating, and the conductivity of copper-plated carbon fibers increases with the decrease of graphitization degree of carbon fibers. The conductivity of copper-plated carbon fibers increases by more than six times when the graphitization degree of carbon fibers decreases by 23.9%. This work provides some benchmark importance for the preparation of highquality copper-plated carbon fibers.
Graphene-modified melamine sponges (RGO-MSs) were prepared, as adsorbents with photothermal conversion ability, utilizing solar energy to achieve heavy oil temperature rise, viscosity reduction, and efficient adsorption recovery of highly viscous oil. The RGO-MSs were prepared through a simple impregnation method. The photothermal performance and heavy oil adsorption performances of RGO-MSs with different densities and thicknesses were observed. It was found that as the density increases, the thermal conductivity of RGO-MS increases too, leading to the increase of the average oil absorption rate. The reduction of thickness is beneficial to improving of the adsorption rate. The prepared RGO-MS with a density of 21.5 mg/cm−3 and a height of 1 cm (RGO-MS-3-1) shows excellent mechanical properties and fatigue resistance. Cyclic adsorption–desorption of RGO-MS-3-1 was achieved through extrusion/ ethanol washing. After 10 cycles of reuse through extrusion, the adsorption capacity decreased from 52.90 to 50.02 g g− 1, with a loss of 5.4%. The material was then washed with petroleum ether and ethanol in turn. Its adsorption capacity can restored to 98.8% of the initial value, showing a promising application prospect on heavy oil leakage treatment. The easily prepared RGO-MS exhibits excellent light absorption and photothermal oil adsorption properties, providing a good solution for the problem of heavy oil leakage at sea.