Boosting Hydrogen Evolution in Neutral Medium by Accelerating Water Dissociation with Ru Clusters Loaded on Mo2CTx MXene

Electrocatalytic hydrogen evolution reaction (HER) in mild neutral medium is a compelling goal for environmentally sustainable energy conversion, but its development is greatly limited by slow kinetics. Platinum group noble metals exhibit ultra-high HER activities, but their scarcity and performance instability restrict wide application. Herein, taking advantage of excellent catalyst carrier properties of 2D-layered transition metal carbides (MXenes), highly dispersed of Ru clusters anchored on Mo₂CT_x MXene are demonstrated as a superior HER electrocatalyst, which is prepared by a facile in situ reduction strategy. The as-prepared Ru/Mo₂CT_x catalyst exhibits a very low overpotential of 73 mV to achieve a current density of −10 mA cm⁻² and Tafel slope of 57 mV dec⁻¹ in neutral medium, surpassing performance of most previously reported MXene-based catalysts. In addition, Ru/Mo₂CT_x catalyst also presents superior stability compared to commercial Pt/C. Experimental results and theoretical calculations indicate that the interaction between Ru clusters modulates the electronic structure of active sites and promotes H₂O dissociation and hydrogen desorption.     

Enhancing the photovoltaic performance with two similar structure polymers as donors by broadening the absorption spectrum and optimizing the molecular arrangement

Ternary organic photovoltaics (OPVs) were fabricated with two polymers (PM6 and D18) as the donor and the fullerene-free small molecule Y6 as the acceptor in an inverted structure. The blueshifted absorption spectrum of neat D18 relative to neat PM6 can enable harvesting of more short and medium wavelength photons in the ternary photoactive layer, which is beneficial to increasing the short-circuit current density (J_SC). The enhancement of the open-circuit voltage (V_OC) of the ternary OPVs can be explained by the deeper HOMO level of D18 than that of PM6, which is beneficial to broadening the energy bandgap. In addition, the combination of the cascade LUMO levels among D18, PM6 and Y6 and the enhanced crystallinity can lead to more efficient exciton dissociation and charge transport within the ternary films. As a result, the power conversion efficiency of the optimize ternary OPV is 15.85%, which is higher than those of the PM6:Y6- and D18:Y6-base binary OPVs (PCEs of 14.70% and 14.95%, respectively). The results indicate that ternary OPVs with a blend of two similar chemical structure polymers as the donor could achieve high performance by broadening the light spectrum and optimizing the phase separation and crystallinity.     

Dynamics of direct and indirect channels to dissociative adsorption

Two limiting dynamic processes leading to dissociative adsorption of hydrogen on W(100) are described. An indirect channel to dissociation is evident at low incident translational energies, and the probability that the precursor will go on to dissociate depends in a complex fashion on the coverage of atomic hydrogen. In addition to the indirect route, a direct channel to dissociation also contributes on the clean surface. Pre-adsorbed nitrogen in the c(2 × 2) structure is shown to block the direct channel to dissociation at low incident translational energies. However, the indirect channel to dissociative adsorption remains intact, and leads to a significantly high initial dissociation probability at low energies (60% at 3.4 meV) to conclude that the precursor must be formed at the W(100)-c(2 × 2)N unit cell.     

Charge Recombination Dynamics in Organic Photovoltaic Systems with Enhanced Dielectric Constant

Increasing the dielectric constant of organic photovoltaic materials to reduce recombination rates has long been pursued, however, material modification often results in the modification of multiple device characteristics, making system comparison difficult. In this study, a fullerene derivative with an increased blend dielectric constant is examined by the addition of a triethylene glycol appendage to the fullerene (TEG‐PCBM). Density functional theory calculations show a small change to the permanent dipole moment between TEG‐PCBM and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₀BM) resulting in similar solubility, morphology, and device performance. TEG‐PCBM is blended with donors P3HT and PTB7‐Th and a comparable performance to PC₆₀BM is found. This model system shows the rarely reported characteristic of an increase in the dielectric constant while leaving its other properties unaltered. Looking at light intensity effects on open‐circuit voltage (V_oc), short‐circuit current (J_sc), and fill factor (FF) along with exciton dissociation efficiency, it is observed that when switching to the TEG‐ modified fullerene derivative, geminate recombination is not reduced, and Shockley–Read–Hall recombination is increased. While triethlyene glycol appendages may prove to be ineffective in improving recombination through increased dielectric constant, an approach for studying recombination in future high dielectric systems is provided.     

甲醇催化裂解气组成调变之应用——65Mn弹簧片回火保护

利用Tc-502型催化剂的双功能,在甲醇中加一定量水调变气氛组成,实现了65Mn弹簧钢片在500℃的回火保护。工件表面不积炭,不氧化。     

pH—pC图的绘制及其意义

本文给出pH-pC图的详细绘制方法。根据这种图解,我们可以看到一元酸(包括强酸)在它的浓度逐步变稀时的离解过程。     

Experimental31p nmr study of the influence of ionic strength on the apparent dissociation constant of mgatp

The classical method for³¹P NMR determination of intracellular free magnesium concentration ([Mg _free ²⁺ ]) requires an accurate knowledge of the apparent dissociation constant (K _D ) of MgATP. There is a large difference between the previously determined values ofK _D . Although the value of 50 µM, determined by a³¹P NMR method, is now largely accepted, a value of 86 µM has more recently been measured with a fitting method derived from the original one, and with a different ionic strength. The purpose of our study was to assess if the cause of the difference between these two previously reportedK _D values was due to the measuring method or to the ionic strength value used.Working at pH=7.2,T=37°C, and [KCl]=0.25 M, we performedK _D measurements with the original³¹P NMR method and with the fitting method. The results (67±13 µM and 61±20 µM, respectively) were not significantly different. Then, with the first method, we measured K_D at [KCl]=0.12 M and found a value of 19±5 µM. We conclude that the main cause of difference between theK _D values measured by³¹P NMR reside in the disparity of ionic strength values used for their measurement. OurK _D measurements at [KCl]=0.25 and 0.12 M demonstrate the importance of the ionic strength value used for imitating the intracellular medium on the absolute value of ([Mg _free ²⁺ ]) measured by³¹P NMR spectroscopy.Address for correspondence: Université Catholique de Louvain, Unité CPMC, Bâtiment Lavoisier, Place Louis Pasteur n°1, B-1348 Louvain-la-Neuve, Belgium. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY 10119.     

低聚表面活性剂——从分子结构水平上调控有序聚集体

阐述当设计不同长短的联接基团链时可控制低聚表面活性剂单元分子内离子头基间的距离，这使单元分子的几何形状，头基电荷密度和水化程度及烷烃链密度发生变化，单元分子的这些变化直接影响低聚表面活性剂分子聚集体的状况，从而实现从分子结构水平上调控分子有序聚集体的形状和表面电荷密度。     

A study on the aliphatic energetic plasticizers containing nitrate ester and nitramine

The aliphatic energetic plasticizers with three and four –CH₂ between nitrate ester and nitramine were synthesized to obtain a plasticizer that is more stable than N-butyl-N-nitratoethyl nitramine (BuNENA) with two –CH₂. First, amino alcohol compounds such as propylamino propanol (PAP) and ethylamino butanol (EAB) as a precursor of energetic plasticizer were synthesized. However, unlike in BuNENA synthesis, various side reactions occurred in the nitration of amino alcohols. Fortunately, it was possible to considerably suppress the formation of side products in the nitration of PAP by using a solvent and an appropriate concentration of nitric acid. In addition, an energetic plasticizer with higher oxygen content was obtained through the nitration of intermediate, amide alcohol, which was formed in the synthesis of EAB.