Hydrogen evolution reaction on in-plane platinum and palladium dichalcogenides via single-atom doping

Searching for the catalysts with excellent catalytic activity and high chemical stability is the key to achieve large-scale production of hydrogen (H₂) through hydrogen evolution reaction (HER). Two-dimensional (2D) platinum and palladium dichalcogenides with extraordinary electrical properties have emerged as the potential candidate for HER catalysts. Here, chemical stability, HER electrocatalytic activity, and the origin of improved HER performance of Pt/Pd-based dichalcogenides with single-atom doping (B, C, N, P, Au, Ag, Cu, Co, Fe, Ni, Zn) and vacancies are explored by first-principles calculations. The calculated defect formation energy reveals that most defective structures are thermodynamically stable. Hydrogen evolution performance on basal plane is obviously improved by single-atoms doping and vacancies. Particularly, Zn-doped and Te vacancy PtTe₂ have a ΔG_H value close to zero. Moreover, defect engineering displays a different performance on HER catalytic activity in sulfur group elements, in order of S < Te < Se in Pd-based chalcogenides, and S < Se < Te in Pt-based chalcogenides. The origin of improved hydrogen evolution performance is revealed by electronic structure and charge transfer. Our findings of the highly activating defective systems provide a theoretical basis for HER applications of platinum and palladium dichalcogenides.     

Employing one-step coupling cold plasma and thermal polymerization approach to construct nitrogen defect-rich carbon nitrides toward efficient visible-light-driven hydrogen generation

Construction of structural defects in photocatalysts is a powerful tool for regulating their photocatalytic performance. In this work, we develop a facile one-step coupling cold plasma and thermal polymerization approach to synthesize a series of nitrogen defect-rich graphitic carbon nitrides (C₃N_4-x), which are used for visible-light-driven hydrogen generation from water. The nitrogen defect-induced band structure regulation of C₃N_4-x catalysts can be carried out through controlling the bombardment time and excitation power of generator during the plasma modification process. The defective C₃N_4-x catalysts have the extended visible light absorption and improved separation efficiency of photogenerated charge carriers, which results in the boosted hydrogen generation activity. Particularly, the optimal C₃N_4-x possesses a hydrogen generation rate of 2.46 mmol h^?1 g^?1, which is about 4.5 times higher than the pristine C₃N₄ synthesized by the single thermal polymerization of urea. The cold plasma modification-based one-step synthesis approach guides us for rationally designing defective nanomaterials with excellent catalytic performance.     

柴油车尾气处理液颗粒原料尿素指标研究

以颗粒尿素为原料生产的柴油车尾气处理液,在气温低的地区使用易出现沉淀物问题,通过对尿素生产工艺的研究和试验分析得知,沉淀物产生的原因为尿素生产蒸发造粒时产生的副产物缩二脲等所造成,当颗粒尿素中的副产物含量偏高时,遇低温就会析出,且该析出反应不可逆;通过进一步试验确定,当固体尿素为原料生产柴油车尾气处理液选用的颗粒尿素原料缩二脲≤0.80％时,是生产尾气处理液产品不出现析出物的关键性指标.目前,该指标已为大多数以颗粒尿素生产柴油车尾气处理液的生产厂家所选用采纳.     

Synthesis and photocatalytic performance of MoS2/Polycrystalline black phosphorus heterojunction composite

As a promising catalyst for solar hydrogen production, black phosphorus (BP) has received widespread attention due to variable band gaps, high carrier mobility, and strong light absorption performance. Herein, we use MoS₂ as a cocatalyst to synthesize BP/MoS₂ catalyst with polycrystalline BP to improve photocatalytic performance under visible light irradiation. A small amount of MoS₂ can reduce the recombination of electron-hole pairs in the composite, increase carrier transport efficiency, and then improve photocatalytic performance. As expected, the 10/0.5 ratio of BP/MoS₂ catalyst exhibits the highest photocatalytic hydrogen evolution performance with a hydrogen evolution rate of 575.4 μmol h^?1 g^?1, which is 2.5 times of pure BP. Based on the results above, a simple method is provided to synthesize low-cost black phosphorus-based photocatalysts.     

Improving storability,physiological disorders,and antioxidant properties of ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) by pre-harvest 1-methylcyclopropene spraying

Ethylene continues to be a major factor influencing quality of European pears during storage. Although research has been done on the effect of pre-harvest 1-methylcyclopropene (1-MCP) on physiological characteristics in pears, a full understanding of cultivar response and antioxidant metabolism remains elusive. Spraying 1-MCP on ‘Bartlett’ and ‘d’Anjou’ pears was studied with respect to physiology, storage and eating quality, disorders, and antioxidant properties at two harvest date (H1 and H2) during storage and ripening. Treatment with 1-MCP extended the harvest window of ‘Bartlett’ and ‘d’Anjou’ pears 3 and 4 days, respectively, without reducing storage or eating quality. Treatment with 1-MCP reduced ethylene production (EPR) and respiration rates (RR), maintained fruit firmness and green colour during storage and retarded development of desirable melting texture in both cultivars. Additionally, 1-MCP lowered the incidence of disorders by alleviating membrane lipid peroxidation, retaining high total flavonoids (TF) and antioxidant capacity, and enhancing superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity in both cultivars. Overall, pre-harvest 1-MCP applications could extend storage time of ‘Bartlett’ and ‘d’Anjou’ pears to 5 and 6 months, respectively, at −1.1 ± 0.5 °C, by reducing ethylene synthesis and enhancing antioxidant metabolism.     

映秀湾电站水轮机转轮沙水流动数值模拟

为了研究映秀湾水电站水轮机内部沙水流动特性,对水轮机进行沙水流动数值模拟,分析水轮机转轮部分沙水流动情况。研究结果表明,转轮内叶片进水边及出水边靠下环处是泥沙分布的主要区域。研究结果对水轮机泥沙磨损的研究具有指导意义。     

Efficient MOF- derived V–Ni3S2 nanosheet arrays for electrocatalytic overall water splitting in alkali

The synergistic achievement of low-cost earth-abundant electrocatalysts and high efficiency to meet renewable energy need is highly desirable yet challenging. Here, we developed a simple Ni foam self -templating route for V-doped Ni₃S₂ nanosheet arrays through in situ formation of metal-organic frameworks (MOFs) combined with subsequent conversion. The as-prepared MOF-V-Ni₃S₂/NF catalyst delivers outstanding electrocatalytic performance in the alkaline solution, which requires low overpotentials of 118.1 mV @10 mA cm^?2 and 268 mV @10 mA cm^?2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. The V-doping and MOF-derived 3D hieratical nanostructure play a vital role in the catalytic process, which provides efficient active sites and large surface areas. Furthermore, an alkaline electrolyzer was assembled with two pieces of MOF-V-Ni₃S₂/NF, which achieves efficient water splitting at 1.58 V @10 mA cm^?2. This strategy opens up new channels to synthesize MOF-based bifunctional electrocatalysts toward overall water spitting.     

Recent progress of green sorbents-based technologies for low concentration CO2 capture

The increased concentration of CO₂ due to continuous breathing and no discharge of human beings in the manned closed space, like spacecraft and submarines, can be a threat to health and safety. Effective removal of low concentration CO₂ from the manned closed space is essential to meet the requirements of long-term space or deep-sea exploration, which is an international frontier and trend. Ionic liquids (ILs), as a widespread and green solvent, already showed its excellent performance on CO₂ capture and absorption, indicating its potential application in low concentration CO₂ capture. In this review, we first summarized the current methods and strategies for direct capture from low concentration CO₂ in both the atmosphere and manned closed spaces. Then, the multi-scale simulation methods of CO₂ capture by ionic liquids are described in detail, including screening ionic liquids by COSMO-RS methods, capture mechanism by density functional theory and molecular dynamics simulation, and absorption process by computational fluid dynamics simulation. Lastly, some typical IL-based green technologies for low concentration CO₂ capture, such as functionalized ILs, co-solvent systems with ILs, and supported materials based on ILs, are introduced, and analyzed the subtle possibility in manned closed spaces. Finally, we look forward to the technology and development of low concentration CO₂ capture, which can meet the needs of human survival in closed space and proposed that supported materials with ionic liquids have great advantages and infinite possibilities in the vital area.     

水泥工厂联合储库智能抓斗行车系统

目前，水泥生产线的原燃料储存及均化，大部分采用的都是配有堆取料机的预均化堆场。其优点是对物料的预均化效果好，但不足之处如占地面积较大，取黏湿物料时效率较低，堆取料机错位时需要人工参与，对实现二代水泥技术对劳动定员的高要求不利。 近年来，随着电控、传感及相关智能技术（如：料位3D模拟、智能生产控制方案）的发展，采用智能抓斗的全自动无人值守联合储库作为一种技术方案正在逐步实现。     

我国装配式建筑技术热点及创新趋势研究——基于专利语义分析方法

从功能角度量化分析中国装配式建筑技术热点及创新趋势.结果 表明:2001-2018年间,中国装配式建筑技术热点主要集中在主体结构的连接、安装集成、支护等方面,结构稳固技术是未来的重点方向;设备管线中减振抗震技术、防水防渗技术热度较高;建筑围护中绿色节能技术是现在和未来的主导方向;内装技术中,整体厨房、整体卫生间等部品装配相关的制动装置和成品保护将成为其发展核心.