SAPO-34提升铁钒基催化剂抗碱性能研究

采用浸渍法制备Fe-VO_x/SAPO-34和Fe-VO_x/TiO₂脱硝催化剂,探究SAPO-34分子筛与TiO₂两种载体负载铁钒基氧化物催化活性及抗碱性能的差异。借助X射线衍射(XRD)、X射线光电子能谱(XPS)、氨气程序升温脱附(NH₃-TPD)、氢气程序升温还原(H₂-TPR)、原位红外漫反射(in-situ DRIFTs)等表征手段对催化剂的骨架结构、表面物化性质、氧化还原能力以及对反应气体的吸脱附情况进行分析。结果表明:SAPO-34分子筛内部特定的孔道结构和稳定的骨架,有利于活性组分在载体上均匀分散,降低碱金属对表面活性中心的物理覆盖作用;同时其表面丰富的酸位点能够作为碱金属捕获位,保护催化剂表面的活性中心,保证催化剂的吸附-反应过程能够正常进行,从而使Fe-VO_x/SAPO-34表现出良好的抗碱金属能力。     

石墨烯负载的氧配位钴单原子稳定金属锂负极

Lithium (Li)-based batteries are the dominant energy source for consumer electronics, grid storage, and electrified transportation. However, the development of batteries based on graphite anodes is hindered by their limited energy density. With its ultrahigh theoretical capacity (3860 mAh∙g⁻¹), low redox potential (−3.04 V), and satisfactorily low density (0.54 g∙cm⁻³), Li metal is the most promising anode for next-generation high-energy-density batteries. Unfortunately, the limited cycling life and safety issues raised by dendrite growth, unstable solid electrolyte interphase, and "dead Li" have inhibited their practical use. An effective strategy is to develop a suitable lithiophilic matrix for regulating initial Li nucleation behavior and controlling subsequent Li growth. Herein, single-atom cobalt coordinated to oxygen sites on graphene (Co-O-G SA) is demonstrated as a Li plating substrate to efficiently regulate Li metal nucleation and growth. Owing to its dense and more uniform lithiophilic sites than single-atom cobalt coordinated to nitrogen sites on graphene (Co-N-G SA), high electronic conductivity, and high specific surface area (519 m²∙g⁻¹), Co-O-G SA could significantly reduce the local current density and promote the reversibility of Li plating and stripping. As a result, the Co-O-G SA based Li anodes exhibited a high Coulombic efficiency of 99.9% at a current density of 1 mA∙cm⁻² with a capacity of 1 mAh∙cm⁻², and excellent rate capability (high current density of 8 mA∙cm⁻²). Even at a high plating capacity of 6 mAh∙cm⁻², the Co-O-G SA electrode could stably cycle for an ultralong lifespan of 1300 h. In the symmetric battery, the Co-O-G SA based Li anode (Co-O-G SA/Li) possessed a stable voltage profile of 18 mV for 780 h at 1 mA∙cm⁻², and even at a high current density of 3 mA∙cm⁻², its overpotential maintained a small hysteresis of approximately 24 mV for > 550 h. Density functional theory calculations showed that the surface of Co-O-G SA had a stronger interaction with Li atoms with a larger binding energy, −3.1 eV, than that of Co-N-G SA (−2.5 eV), leading to a uniform distribution of metallic Li on the Co-O-G SA surface. More importantly, when matched with a sulfur cathode, the resulting Co-O-G SA/lithium sulfur full batteries exhibited a high capacity of 1002 mAh∙g⁻¹, improved kinetics with a small polarization of 191 mV, and an ultralow capacity decay rate of 0.036% per cycle for 1000 cycles at 0.5C (1C = 1675 mA∙g⁻¹) with a steady Coulombic efficiency of nearly 100%. Therefore, this work provides novel insights into the coordination environment of single atoms for the chemistry of Li metal anodes for high-energy-density batteries.     

g-C3N4-W18O49复合光催化剂的制备及其光催化机理研究

通过简单的溶剂热法成功制备出了g-C3N4-W18O49复合光催化剂,采用XRD、SEM、TEM以及PL对所得催化剂的物相结构及形貌和光学性能进行了表征,通过降解甲基橙和光解水产氢实验研究所得催化剂的催化性能及其催化机理.由实验可知,W18O49的含量为50;时所得g-C3N4-W18O49复合光催化剂的降解性能最好,其降解率比纯g-C3N4纳米片提高48;;为进一步研究复合光催化剂的电子-空穴传输机理,我们又进行了光解水制氢实验.结果表明:单一的W18O49无产氢活性,它的复合明显降低了g-C3N4的产氢速率,说明复合结构中光生电子是从g-C3N4传递到了W18O49,表现出明显的Ⅱ型异质结复合特征,而不是部分文献所提出的Z型方式.     

基于响应面法的直拉硅单晶生长工艺参数优化方法

在直拉法制备硅单晶的过程中,要得到优质的晶体必须建立合理的温度分布,而单晶炉内热场的分布与工艺参数的设定密切相关.其中以晶体转速、坩埚转速和拉速等三个工艺参数对热场分布的影响尤为显著.为了确定最佳热场分布下晶转、埚转及拉速的设定值,本文采用响应面算法通过方程拟合、回归分析等步骤求解这三个工艺参量与温度梯度之间的最佳函数模型,并在该模型下同时对这三个工艺参量进行优化分析,且通过仿真实验和拉晶实验表明该方法的有效性.     

ZnO-PSAⅡ型异质结界面电荷转移过程研究

采用稳态光致发光光谱和纳秒时间分辨瞬态光谱(NTRT-PL)表征,揭示ZnO-PSA II型纳米异质结光生载流子电荷转移过程,通过甲基橙光降解实验,测得ZnO-NRs和ZnO-PSA紫外光降解率分别为25.5;和60.1;,光降解率提高到2.4倍,表明II型异质结相对于单一半导体而言,能促进光生载流子在界面间电荷转移,有利于载流子的分离.     

二维共价三嗪框架膜的制备及其分子分离性能

二维共价三嗪框架材料(2D-CTF)可作为一类理想的二维分离膜基元体。本文利用微界面法制备了具有寡层结构的2D-CTF-1纳米材料,并以其为基元体构筑超薄层状2D-CTF-1分离膜。采用傅里叶红外光谱、X射线光电子能谱、原子力显微镜、透射电子显微镜和扫描电子显微镜对2D-CTF-1纳米材料及其组装成的分离膜进行结构与形貌表征,并测试2D-CTF-1分离膜在不同压力下的纯水通量以及对染料小分子的分离性能。结果表明:2D-CTF-1分离膜的纯水通量可达153.7 L/(m2·h)(25℃,0.1 MPa),二维面内结构孔为主要的水分子传输通道,对染料小分子刚果红的渗透通量为132.5 L/(m2·h)(25℃,0.1 MPa),截留率为98.3%。2D-CTF-1分离膜在长时间连续运行后仍能维持较高通量和96%以上的截留率,是一类极具潜力的新型二维分离膜材料。     

氧化锌电阻阀片中ZnO(002)/β-Bi_2O_3(210)界面结构的第一性原理研究

为了从物质微观结构上了解氧化锌避雷器阀片的性能,采用基于密度泛函理论的第一性原理方法对ZnO(002)/β-Bi_2O_3(210)界面结构进行弛豫和电子结构计算.结果表明弛豫后,原子间的键长发生改变.界面区域差分电荷密度图和原子布居分析可得ZnO层片中Zn原子电荷缺失,β-Bi_2O_3层片中O原子电荷富集,ZnO层片向β-Bi_2O_3层片转移电子电荷23.61e.晶界结构的内建电场由ZnO层片指向β-Bi_2O_3层片,内建电场是ZnO电阻阀片具有非线性伏安特性的重要原因.界面附近态密度表明界面的结合主要依靠ZnO层片中Zn原子与β-Bi_2O_3层片中O原子相互作用.计算显示ZnO(002)/β-Bi_2O_3(210)界面结合较强,界面能约为-4.203 J/m~2.本文研究结果对于研制高性能非线性伏安特性氧化锌电阻片提供了机理解释和理论支持.