Cr⁴⁺∶YAG固体激光器的频率稳定性分析

Cr4+∶YAG固体激光器的很多应用要求激光器的频率非常稳定。文章从反映Cr4+∶YAG固体激光器的频率特性的方程出发,定量分析了激光器工作的环境温度、大气及湿度等因素的变化对激光器的频率波动的影响,提出可采用Pound-Drever系统对Cr4+∶YAG激光器进行主动稳频

碳化钒改性镍基催化剂的尿素电氧化性能

尿素电解法以其在含尿素废水处理及制氢领域的节能环保前景而受到广泛关注，关键在于设计高效稳定的尿素电氧化催化剂。文中设计开发一种VC(碳化钒)改性的Ni-VC/MWCNTs(Ni基纳米复合催化剂)用于尿素电氧化可达到343.3 mA/mg的优异电流密度，其与Ni/MWCNTs催化剂相比具有更小的Tafel斜率和更低的电荷转移电阻。此外，在稳态条件下，Ni-VC/MWCNTs催化剂的电流密度也得到提高。X射线光电子能谱测试表明引入VC使得Ni更易失电子生成活性组分NiOOH,从而增强尿素电氧化性能。此外，在尿素电解池中，达到10 mA/cm~2的电流密度，以Ni-VC/MWCNTs作为阳极催化剂所需的电压比Ni/MWCNTs降低了近100 mV。结果表明Ni-VC/MWCNTs是一种优良的尿素电解催化剂，有望实现高效制氢和废水资源化利用。 Urea electrolysis has attracted wide attention for its energy-saving and environmentally friendly prospects in the fields of urea-containing wastewater treatment and hydrogen production. The key issue is the design of efficient and stable catalysts for urea electrooxidation. The synthesis of VC (vanadium carbide) modified nickel- based catalysts supported on multi-walled carbon nanotubes (Ni-VC/MWCNTs) for UOR (urea electrooxidation reaction) was reported. Ni-VC/MWCNTs has a superior current density of 343. 3 mA/mg. Particularly, Ni-VC/ MWCNTs has a smaller Tafel slope and a lower charge transfer resistance compared with Ni/MWCNTs. Moreover, the current density under the steady state of Ni-VC/MWCNTs is also enhanced. XPS (X-ray photoemission spectroscopy) demonstrates that the introduction of VC makes Ni more susceptible to lose electrons to form the active component NiOOH, which improves the UOR performance. Furthermore, in the urea electrolytic cell, the voltage required to supply 10 mA/cnr with Ni-VC/MWCNTs as the anode is reduced by nearly 100 mV compared with Ni/MWCNTs. The result suggests Ni-VC/MWCNTs is an efficient catalyst for urea electrolysis, which is expected to high-efficiency hydrogen production and resourceful utilisation of wastewater. © 2024 Editorial Office of Chemical Engineering (China). All rights reserved

直接尿素燃料电池研究进展

Direct urea fuel cells (DUFCs) can simultaneously treat urea-containing wastewater (urine, etc.) and generate electricity. Ni-based materials are effective catalysts for anodic urea electrooxidation reaction (UOR). However, the complex and sluggish kinetics of UOR lead to low activity and poor stability of Ni-based catalysts, resulting in generally lower power density of DUFCs. The key to realizing the application of DUFCs lies in the modification of Ni-based catalysts, constructing efficient and stable catalyst layers and the related membrane electrode assemblies (MEA). Therefore, the research progress of anode catalysts assembled into DUFCs was reviewed in detail. Furthermore, the effect mechanism (including the support effect and synergistic effect) on the DUFC performance of the composition structure for the modified catalysts was deeply analyzed. The review aims to provide a scientific basis for the efficient and stable UOR catalyst design. In addition, the research progress of the membrane materials in DUFC systems and the fabrication of the MEA were described. Finally, the research priorities and future directions in this field were summarized and proposed, which contributed to the development of high-performance DUFCs achieving commercialization. © 2023 Editorial Office of Chemical Engineering (China). All rights reserved

尿素電氧化協同析氫反應雙功能催化劑研究進展

尿素電解技術通過耦合陽極電化學尿素氧化與陰極協同產氫，對富尿素廢水綠色處理和節能制氫具有重要意義，其應用的關鍵在于設計構筑高效且穩定的UOR（尿素氧化反應）和HER（析氫反應）催化劑。若采用對UOR和HER均有效的雙功能催化劑，不僅能簡化電解槽構造，還可有效避免陽極和陰極不同催化劑之間固有的不相容性及其引發的副反應。基于此，綜述尿素電解雙功能催化劑的研究進展，分類評述鎳基（氮化鎳、磷化鎳、硫化鎳、氧化鎳及其復合材料）、鈷基和鎳-鈷基雙功能催化劑的設計開發策略和性能強化機制，歸納典型尿素電解雙功能催化劑的UOR/HER特性及其電解槽性能，并展望其未來的發展方向，旨在為推動尿素電解雙功能催化劑的應用提供借鑒。 Urea electrolysis technology achieves the synergistic hydrogen production at the cathode by coupling anodic electrochemical urea Oxidation. It is of great importance for green treatment of urea-rich wastewater and energy-saving hydrogen production. The key to its application lies in the design and construction of efficient and stable UOR (urea Oxidation reaction) and HER (hydrogen evolution reaction) catalysts. Compared with adopting different catalysts, the use of bifunctional catalysts active for UOR and HER not only simplifies the electrolyzer configuration, but also effectively avoids the inherent incompatibility and the side reactions triggered by different catalysts at the anode and cathode. For this reason, the research progress of bifunctional catalysts for urea electrolysis was reviewed. Furthermore, the design development strategies and Performance reinforcement mechanisms of nickel-based (nickel nitride, nickel phosphide, nickel sulfide, nickel oxide and their composites), cobalt-based and nickel-cobalt-based bifunctional catalysts were categorically reviewed. In addition, the UOR/HER characteristics and electrolyzer Performances of the typical bifunctional catalysts for urea electrolysis were summarized. Finally, the future directions of bifunctional catalysts for urea electrolysis are prospected, aiming to provide a reference for promoting its applications. © 2024 Editorial Office of Chemical Engineering (China). All rights reserved

Determination of the number of ψ(3686) events taken at BESIII

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×10^