四元化合物半导体Cu2ZnSnS4:结构、制备、应用及前景

四元化合物半导体铜锌锡硫(Cu₂ ZnSnS₄,CZTS)由于其四种组成元素在地壳中丰度非常高且安全无毒,因而成本低廉。CZTS作为直接带隙半导体材料,其吸收光谱与太阳辐射光谱匹配性好、光吸收系数高,具有结构与性质可调可控、光电性能优异等优势,是发展绿色、低成本、高效率和稳定薄膜太阳电池的理想核心材料。近年来,国内外研究者对CZTS的结构与性质、制备工艺、应用尤其是通过结构、成分的调控提高其光电转换效率等方面进行了广泛的研究和探讨。本文对CZTS的结构演变、制备工艺、光电性质与应用等进行综述,重点分析了晶体结构、缺陷、表面与界面、合金化等因素对其光伏性能的影响。同时,对CZTS作为新型能量转换材料在光催化和热电等领域的应用进行了探讨。最后对CZTS目前存在的挑战和今后的研究重点进行总结并展望了将来可能的突破方向。     

东胜长焰煤热解含氧官能团结构演化的13C-NMR和FT-IR分析

以东胜煤田色拉一号井田2号煤层长焰煤为研究对象,利用浮沉离心法富集其镜质组。基于工业分析、元素分析、¹³C-NMR、FT-IR、谱图分峰拟合技术和化学分析测试,求取镜煤及一系列热解煤含氧官能团结构与含量参数,从不同角度研究了含氧官能团的分布规律与演化特点。镜煤中羧基、羰基含量分别为8.91~10.90 mol/kg、1.61~1.79 mol/kg,随热解温度升高羧基显著减少。热解作用促使以端基形式连接在脂肪链或脂肪环结构氧上的甲基和亚甲基首先脱去,且在温度高于350 ℃后基本稳定。氧在热解过程赋存状态的变化是芳香体系与脂肪体系相互竞争的结果,510 ℃热解煤中芳香类氧和脂肪类氧的含量分别为7.49、3.45 mol/kg。羟基的演化过程与热解过程中氧的赋存状态密切相关。随着热解过程的进行,在热解温度低于440 ℃时,各种羟基含量均减少,热解过程对于大分子网络的破坏干扰了各种氢键作用,而羟基π作用则暂时增强,至510 ℃时各种氢键含量均降为最低。东胜长焰煤中含氧官能团化学活性顺序为:[COOH]>[R-O]>[Ar-O-Ar,Ar-O-C,C-O-C]>[C=O]。镜煤非活性醚键含量为0.68 mol/kg,活性醚键为0.48 mol/kg,主要为非活性醚键。     

Electrochemical behavior of kryptand 222 on a mercury electrode

The electrochemical behavior of kryptand 222 at the interface between a mercury electrode and an aqueous solution is studied by the impedance spectroscopy, polarography, and cyclic voltammetry methods. It is established that kryptand 222 possesses high surface activity at this interface. Adsorption parameters of kryptand 222 are found on the basis of the model of two parallel capacitors supplemented by the Frumkin isotherm by the regression analysis method. The potential dependences of the differential capacitance (C,E curves), calculated using these parameters satisfactorily agree with experiment. It is shown that the maximum in the C,E curves in the region of negative potentials is caused by catalytic process of hydrogen evolution.     

Devisable POM/Ni Foam Composite: Precisely Control Synthesis toward Enhanced Hydrogen Evolution Reaction at High pH

Polyoxometalates (POMs) are promising catalysts for the electrochemical hydrogen production from water owing to their high intrinsic catalytic activity and chemical tunability. However, poor electrical conductivity and easy detachment of the POMs from the electrode cause significant challenges under operating condition. Herein, a simple one-step hydrothermal method is reported to synthesize a series of Dexter–Silverton POM/Ni foam composites (denoted as Ni M -POM/Ni; M =Co, Zn, Mn), in which the stable linkage between the POM catalysts and the Ni foam electrodes lead to high activity for the hydrogen evolution reaction (HER). Among them, the highest HER performance can be observed in the NiCo-POM/Ni, featuring an overpotential of 64 mV (at 10 mA cm⁻², vs. reversible hydrogen electrode), and a Tafel slope of 75 mV dec⁻¹ in 1.0 m aqueous KOH. Moreover, the NiCo-POM/Ni catalyst showed a high faradaic efficiency ≈97 % for HER. Post-catalytic of NiCo-POM/Ni analyses showed virtually no mechanical or chemical degradation. The findings propose a facile and inexpensive method to design stable and effective POM-based catalysts for HER in alkaline water electrolysis.     

In Situ Pyrolysis Tracking and Real-Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon

The in situ tracking of the pyrolysis of a binary molecular cluster [Zn₇(μ₃-CH₃O)₆(L)₆][ZnLCl₂]₂ is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2-methoxy-6-((methylimino)-methyl)phenolate) to porous carbon using TG-MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real-time-dependent phase-sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano-sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m² g⁻¹ and pore volume of 0.926 cm³ g⁻¹ exhibits the best known capacitance of 662 F g⁻¹ at 0.5 A g⁻¹.     

Ultrathin,Porous and Oxygen Vacancies‐Enriched Ag/WO3−x Heterostructures for Electrocatalytic Hydrogen Evolution

Exploring advanced electrocatalysts for electrocatalytic hydrogen evolution is highly desired but remains a challenge due to the lack of an efficient preparation method and reasonable structural design. Herein, we deliberately designed novel Ag/WO_3?x heterostructures through a supercritical CO₂‐assisted exfoliation‐oxidation route and the subsequent loading of Ag nanoparticles. The ultrathin and oxygen vacancies‐enriched WO_3?x nanosheets are ideal substrates for loading Ag nanoparticles, which can largely increase the active site density and improve electron transport. Besides, the resultant WO_3?x nanosheets with porous structure can form during the electrochemical cycling process induced by an electric field. As a result, the exquisite Ag/WO_3?x heterostructures show an enhanced hydrogen evolution reaction (HER) activity with a low onset overpotential of ≈30 mV, a small Tafel slope of ≈40 mV dec^?1 at 10 mA cm^?2, and as well as long‐term durability. This work sheds light on material design and preparation, and even opens up an avenue for the development of high‐efficiency electrocatalysts.     

Stress‐Transfer‐Induced In Situ Formation of Ultrathin Nickel Phosphide Nanosheets for Efficient Hydrogen Evolution

Ultrathin two‐dimensional (2D) nanostructures have attracted increasing research interest for energy storage and conversion. However, tackling the key problem of lattice mismatch inducing the instability of ulreathin nanostructures during phase transformations is still a critical challenge. Herein, we describe a facile and scalable strategy for the growth of ultrathin nickel phosphide (Ni₂P) nanosheets (NSs) with exposed (001) facets. We show that single‐layer functionalized graphene with residual oxygen‐containing groups and a large lateral size contributes to reducing the lattice strain during phosphorization. The resulting nanostructure exhibits remarkable hydrogen evolution activity and good stability under alkaline conditions.     

从铁状态的变化研究球性活性炭中孔形成的机理

利用穆斯堡尔谱、透射电子显微镜等表征手段研究了添加二茂铁后酚醛树脂基球形活性炭中孔形成的机理。结果表明,添加到酚醛树脂中的二茂铁在炭化阶段被还原为单质铁。单质铁对炭－反应有催化气化作用。在活化阶段,铁粒子周围的炭基体与水蒸汽的活化反应速率快,被刻蚀掉更多的炭,所以在其周围形成中孔。     

Pt—TiO2光催化还原罗丹明B

报道了罗丹明B（RhB)在TiO2催化剂上的吸附过程及加氢反应结构。当草酸作为电给体时,光催化反应产生的氢气,可使RhB发生快速地氢反应,生成无色的加氢产物。该加氢过程与催化剂的种类、表面化学状态和担载催化剂的种类有密切关系。     

低同源性蛋白质结构预测

基因组计划在实施产生了大量的DNA序列信息,如何有效地利用这些信息来研究基因的产物－蛋白质的结构与功能成为引入注目的研究领域,同源蛋白质结构预测及蛋白质折工识别是在基因组水平上进行蛋白质结构预测的有效方法,酵母基因组中约有50％的基因可以通过这类方法来确定其表面产物蛋白质的结构[1],但是目前所采用的方法在低同源性蛋白质的结构预测方面尚存在较大困难。