Superconducting LaRu2P2 and other alkaline earth and rare earth metal ruthenium and osmium phosphides and arsenides with ThCr2Si2 structure

The ThCr₂Si₂-type compounds MRu₂P₂ (M = Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), MOs₂P₂ (M = Sr, Ba, Eu), and MRu₂As₂ (M = Ca, Sr, Ba, La, Eu) were prepared by sintering techniques and/or by reaction of the elemental components in a tin flux. The crystal structures of SrRu₂P₂ and LaRu₂P₂ were refined from single-crystal diffractometer data to residuals of R = 0.019 (224 structure factors, 11 variable parameters) and R = 0.028 (510 F's, 11 variables), respectively. LaRu₂P₂ is diamagnetic and becomes superconducting at 4.1 K. No transition to a superconducting state was observed down to 1.8 K for the compounds MFe₂P₂ (M = Ca, Sr, Ba, La), MRu₂P₂ (M = Ca, Sr, Ba, Y), and MOs₂P₂ (M = Sr, Ba).     

Studies on the thermal decomposition of phosphides and arsenides of silicon and of germanium

The thermal decomposition in vacuum of phosphides and arsenides of silicon and germanium has been investigated using a simple set-up designed to resist the attack of the corrosive decomposition products. The phases GeP, GeAs, SiAs₂ and GeAs₂ disintegrate directly to the elements. X-ray amorphous intermediary products Si_≈5P and Si₆As are formed when SiP and SiAs are heated to 940 to 930°C, respectively. The electron diffraction pattern of Si₆As is reported.     

Preparation, structure, and properties of new ternary rhenium arsenides and phosphides with metal-metal bondings

The M₂Re₅As₁₂ arsenides (M = Fe, Co, Ni) and the Co₂Re₅P₁₂ phosphide were synthesized. The unit cell is orthorhombic with space group Pnnm and contains two formula units. The X-ray structure of Ni₂Re₅As₁₂ was studied from three-dimensional single-crystal counter data and was refined down to R = 0.048 for 637 independent reflections. The structure can be described as built up from two different structural domains; the first one is the marcasite type and shows As---As pairs and linear Re---Re chains, the second one consists of Re₄ clusters with common edges linked to terminal Ni atoms. A nearly temperature-independent paramagnetism and p-type metallic conduction were observed from the magnetic and electrical measurements. Also observed in this new family of compounds were the resistivities along and perpendicular to the c axis and their anisotropic behavior.     

Matrix isolation ESR and theoretical studies of metal phosphides

The ZnP, (67)ZnP, CdP, (111)CdP, and (113)CdP radicals have been formed by laser ablation of the metal with GaP pressed into the metal surface, isolated in an inert neon matrix at 4.3 K and their electronic structure was established using electron spin resonance spectroscopy. The following magnetic parameters were determined experimentally for ZnP/(67)ZnP, g(⊥)=1.9982(2), A(⊥)(P)=111(6)?MHz, A(⊥)((67)Zn)=160(2)?MHz, and D=-29?988(3)?MHz and estimates were made for the following ZnP/(67)ZnP magnetic parameters: g(∥)=1.9941(2), A(∥)(P)=-5(6)?MHz, and A(∥)((67)Zn)=180(50)?MHz. The following magnetic parameters for CdP/(111)CdP/(113)CdP were determined experimentally: g(⊥)=1.9963(2), A(⊥)(P)=97(3)?MHz, A(⊥)((111)Cd)=862(3)?MHz, and A(⊥)((113)Cd)=902(3)?MHz. Evidence for the formation of the MgP radical was also obtained and an approximate hyperfine coupling constant of A(⊥)(P)=157(6)?MHz was determined. The low-lying electronic states of ZnP and MgP were also investigated using the multiconfigurational self-consistent field technique. Potential energy surfaces, binding energies, optimized bond lengths, energy separations, and dissociation energies have been determined. Both radicals are found to have (4)Σ(-) ground states with a leading configuration at r(e) of 10σ(2)11σ(2)5π(1)5π(1)12σ(1) for ZnP and 7σ(2)8σ(2)3π(1)3π(1)9σ(1) for MgP. Significant mixing to this state is calculated for MgP.     

Transition metal phosphides: A wonder catalyst for electrocatalytic hydrogen production

Hydrogen evolution from water electrolysis has become an important reaction for the green energy revolution. Traditional precious metals and their compounds are excellent catalysts for producing hydrogen; however, their high cost limits their large-scale practical application. Therefore, the development of affordable electrocatalysts to replace these precious metals is important. Transition metal phosphides(TMPs) have shown remarkable performance for hydrogen evolution and garnered considerable ...     

Recent advances of metal phosphides for Li-S chemistry

Li-S batteries have been considered as one of advanced next-generation energy storage systems owing to their remarkable theoretical capacity(1672 m Ah g^-1)and high energy density(2600 Wh kg^-1).However,critical issues,mainly pertaining to lithium polysulfide shuttle and slow sulfur reaction kinetics,have posed a fatal threat to the electrochemical performances of Li-S batteries.The situation is even worse for high sulfur-loaded and flexible cathodes,which are the essential components for practical Li-S batteries.In response,the use of metal compounds as electrocatalysts in Li-S systems have been confirmed as an effective strategy to date.Particularly,recent years have witnessed many progresses in phosphidesoptimized Li-S chemistry.This has been motivated by the superior electron conductivity and high electrocatalytic activity of phosphides.In this tutorial review,we offer a systematic summary of active metal phosphides as promoters for Li-S chemistry,aiming at helping to understanding the working mechanism of phosphide electrocatalysts and guiding the construction of advanced Li-S batteries.     

1,2-Distanna-closo-dodecaborate--a rare example of a 1,2-distannylene ligand in transition metal chemistry

The coordination chemistry of the novel bidentate tin ligand 1,2-distanna-closo-dodecaborate is illustrated for the first time by reactions with molybdenum, platinum and gold metal complexes. Up to three clusters coordinate two metal centers in close proximity. For all these metal complexes the typical μ-bridging coordination mode was observed exclusively. Furthermore, two cluster anions react with dichloromethane via substitution of the chloride ions. The carbon functionalized tin cluster [Et(4)N](2)[CH(2)(Sn(2)B(10)H(10))(2)] and the coordination complexes [Et(3)NMe](6)[Mo(2)(CO)(6)(Sn(2)B(10)H(10))(3)], [Et(3)NMe](2)[{HPt(PEt(3))(2)(Sn(2)B(10)H(10))}(2)], [Et(4)N](2)[{HPt(PPh(3))(2)(Sn(2)B(10)H(10))}(2)] and [{(TP)Au}(2)(Sn(2)B(10)H(10))] (TP = PhP(o-Ph(2)PC(6)H(4))(2)) are fully characterized by multinuclear NMR spectroscopy, elemental analyses and crystal structure analyses.     

优化金属磷化物电催化析氢性能的策略

日益严重的能源危机和环境污染问题使得探索清洁的可再生能源载体及减少对传统化石燃料的过度依赖成为人们面临的一项重要任务.因此,各种可持续能源如太阳能、风能、海洋能和生物质能等得到了广泛研究并取得了一定的进展.然而,这些能源因存在间歇性和不稳定性等缺点阻碍了其实际应用.近年,氢气作为一种能源载体,以其高能量密度和无碳排放的优点引起了人们的广泛关注,被认为是缓解日益严重的污染问题的最有前途的环保能源.对比目前采用的天然气热解和煤炭气化等传统制氢策略,电催化水裂解由于催化效率高,制氢纯度高和不产生温室气体,被认为是高效、环保、可持续的制氢策略.电催化水裂解由两个独立的半反应组成,分别是析氢反应和析氧反应.析氢反应作为水裂解的一个半反应,在降低制氢成本及提高产氢催化效率方面起着关键作用.然而,目前的核心问题之一是要开发高效的析氢电催化剂,以加快反应速度.目前,铂和铂基纳米材料被认为是高效的析氢电催化剂,但是其稀缺性和高成本阻碍了大规模实际应用.金属磷化物由于具有较高的本征活性并且在不同的电解质中都具有良好的电催化析氢性能,被证明是一种优良的析氢电催化剂.此外,与普通催化剂相比,金属磷化电催化剂还具有合成简便、效率高、成本低、省时等优点.本文详细介绍了近年人们在金属磷化物用于电催化析氢研究中取得的进展.首先,介绍了电催化析氢反应机理,金属磷化物的结构及作用,并对其优缺点进行了总结;随后,综述了金属磷化物的合成方法,包括后处理、原位生成和电沉积策略,并对不同方法进行了比较和讨论.此外,从元素掺杂、界面工程、空穴工程、修饰特定载体、构建特定纳米结构、设计双或多金属磷化物和其他发展的新方法等七个方面详细总结了促进金属磷化物电催化活性的多种策略,并进行了对比和讨论.最后,归纳了金属磷化物在电催化析氢应用中存在的问题和面临的挑战,并对未来的研究发展提出了展望.     

A new insight into the promoting effects of transition metal phosphides in methanol electrooxidation

The construction of highly active catalysts for methanol oxidation reaction (MOR) is central to direct methanol fuel cells. Tremendous progress has been made in transition metal phosphides (TMPs) based catalysts. However, TMPs would be partially damaged and transformed into new substances (e.g., Pt-M-P composite, where M represents a second transition metal) during Pt deposition process. This would pose a large obstacle to the cognition of the real promoting effects of TMPs in MOR. Herein, Co₂P co-catalysts (Pt-P/Co₂P@NPC, where NPC stands for N and P co-doped carbon) and Pt-Co-P composite catalysts (Pt-Co-P/NPC) were controllably synthesized. Electrocatalysis tests show that the Pt-Co-P/NPC exhibits superior MOR activity as high as 1016 mA/mg_Pt, significantly exceeding that of Pt-P/Co₂P@NPC (345 mA/mg_Pt). This result indicates that the promoting effect is ascribed primarily to the resultant Pt-Co-P composite, in sharply contrast to previous viewpoint that Co₂P itself improves the activity. Further mechanistic studies reveal that Pt-Co-P/NPC exhibits much stronger electron interaction and thus manifesting a remarkably weaker CO absorption than Pt-P/Co₂P@NPC and Pt/C. Moreover, Pt-Co-P is also more capable of producing oxygen-containing adsorbate and thus accelerating the removal of surface-bonded CO*, ultimately boosting the MOR performance.     

Kinetic bromine isotope effect: example from the microbial debromination of brominated phenols

The increasing use of kinetic isotope effects for environmental studies has motivated the development of new compound-specific isotope analysis techniques for emerging pollutants. Recently, high-precision bromine isotope analysis in individual brominated organic compounds was proposed, by the coupling of gas chromatography to a multi-collector inductively coupled plasma mass spectrometer using strontium as an external spike for instrumental bias correction. The present study, for the first time, demonstrates an application of this technique for determining bromine kinetic isotope effects during biological reaction, focusing on the reductive debromination of brominated phenols under anaerobic conditions. Results show bromine isotope enrichment factors (ε) of ?0.76?±?0.08, ?0.46?±?0.19, and ?0.20?±?0.06?‰ for the debromination of 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol, respectively. These values are rather low, yet still high enough to be obtained with satisfying certainty. This further implies that the analytical method may be also appropriate for future environmental applications.     

过渡金属磷化物的制备与光/电催化的应用研究进展

过渡金属磷化物(TMPs)价廉易得,因其独特的结构特征具有丰富的活性位点、良好的导电性和结构稳定性,逐渐在催化领域引起了人们的广泛关注,被应用于有机物硫化、脱氢、电催化、光催化等方面.本文主要综述了过渡金属磷化物的结构特征、常用的制备方法以及在电催化和光催化方向应用的最新进展.     

Reactions of metal halide-alkoxides

A method has been developed for the synthesis of esters of thiophene-2,5-diglyoxylic acid from iodomagnesium derivatives of thiophene-2,5-dicarbinols. The formation of products of the second stage of the reaction-2,2-di(alkoxalyl)-5,5-oxalyldithiophenes-has also been established. The IR spectra of the compounds obtained have been studied.For Communication XXIV, see [7].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 898–899, July, 1970.     

An approach to preparing porous and hollow metal phosphides with higher hydrodesulfurization activity

This paper describes an effective method for the synthesis of metal phosphides. Bulk and supported Ni₂P, Cu₃P, and CoP were prepared by thermal treatment of metal and the amorphous red phosphorus mixtures. Porous and hollow Ni₂P particles were also synthesized successfully using this method. The structural properties of these products are investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP-AES) and X-ray photoemission spectroscopy (XPS). A rational mechanism was proposed for the selective formation of Ni₂P particles. In experimental conditions, the Ni₂P/SiO₂ catalyst exhibits excellent hydrodesulfurization (HDS) activity for dibenzothiophene (DBT).     

Reactions of halogen metal alkoxides

The study of the thermal stability of halogen-magnesium alkoxy-carbinolates was continued. The data obtained led to the development of procedures for the synthesis of esters of α-oxo and of α-hydroxy-acids containing the thienyl radical. An intramolecular hydrogen bond between the sulfur atom and the hydrogen of the hydroxyl group in esters of (5-bromothienyl-2)glycolic acid was revealed. The presence of this bond was confirmed by infrared spectroscopic data and by the results of the investigation of the esters of (thienyl-3)- and (4-bromothienyl-3)glycolic acids.     

Reactions of halogen metal alkoxides

The study of the thermal stability of halogen-magnesium alkoxy-carbinolates was continued. The data obtained led to the development of procedures for the synthesis of esters of -oxo and of -hydroxy-acids containing the thienyl radical. An intramolecular hydrogen bond between the sulfur atom and the hydrogen of the hydroxyl group in esters of (5-bromothienyl-2)glycolic acid was revealed. The presence of this bond was confirmed by infrared spectroscopic data and by the results of the investigation of the esters of (thienyl-3)- and (4-bromothienyl-3)glycolic acids.For part XXII, see [4].     

Phenol-formaldehyde resin route to the synthesis of several iron group transition metal phosphides

Abstract

A series of iron, cobalt and nickel metal phosphides of chemical formula Fe_xP, Co₂P and Ni₂P with high specific surface areas of 331.1, 294.2 and 228.0 m² g^?1, respectively, was firstly synthesized by phenol-formaldehyde resin route. It was found that the as-prepared Co₂P and Ni₂P samples synthesized using phenol-formaldehyde resin as a carbon source showed much higher BET surface areas than those prepared using other carbon sources reported before, including cinnamic strong alkali anion exchange resin, p-phenylenediamine and hexamethylenetetramine. This phenol-formaldehyde resin route was proved to be as universal as traditional H₂ reduction method.