基于过渡金属二硫族化物析氢催化的研究进展

解决全球气候变化和能源危机的有效途径之一是用氢能源(H₂)代替传统的化石能源. 析氢反应(Electrochemical hydrogen evolution reaction, HER) 被认为是绿色环保的可持续产氢途径, 通常电解过程需要催化剂以降低电化学电位, 提高能量利用效率. 目前最先进的催化剂仍然依赖于贵金属, 但是研究表明, 过渡金属二硫族化物(Transition metal dichalcogenides, TMDs)同样具有优异的催化活性, 与贵金属相比, TMDs产量大、 价格低、 催化活性好、 便于调控和修饰, 有望替代贵金属在催化领域的应用. 基于此, 本文讨论了近年来TMDs在析氢方面的研究情况以及TMDs材料的性能调控, 包含原子工程、 相工程和异质结. 并总结和展望了TMDs催化材料的挑战与机遇.     

Solution extraction of transition and post-transition heavy and precious metals by chelate and macrocyclic ligands

This review focuses on compounds and methods that can be used for the extraction and separation from solution of two classes of elements that we define as heavy metals and precious metals. These elements are often targeted because they are toxic, costly, and their coordination chemistry has already been well studied, and because there is a need to develop methods of economically extracting, separating and recovering them from waste sites. This review outlines possible strategies that can be used, and reviews the present literature regarding the available methods for their extraction.     

Referee analysis of precious metal sweeps and related materials

Sweeps samples are often complex mixtures containing from trace amounts to 20% of one or more precious metals distributed in matrices consisting of widely varying mixtures of base metals or their oxides. Three collection procedures are described that are suitable for the isolation of precious metals from base substances. One is based on direct fusion of the sample (high-grade sweeps) with sodium peroxide, and the others on collection of the precious metals by fire-assay techniques using either nickel sulphide or silver. The precious metals are then determined either gravimetrically or by atomic-absorption or plasma-emission spectrometry.     

Functionalization of Carbon Nanotube-Supported Precious Metal Catalysts by Coverage with Metal Oxide Layers

Precious metals such as Pd, Pt, and Rh have been utilized as the active components of many catalysts. Owing to the high cost of these metals, their loadings in catalysts must be reduced. However, reducing loadings without compromising catalytic performance is difficult. Precious metal catalysts are inevitably deactivated by severe reaction conditions (e.g., high temperature and pressure), which tend to increase of the size of the precious metal particles. Here, we review our recent work on the functionalization of supported precious metal catalysts by coverage with layers of metal oxides such as silica. Coverage with silica layers a few nanometers thick prevents aggregation of the metal particles as well as their detachment from the supports under severe reaction conditions. For example, coverage of supported Pt and Pd electrocatalysts in polymer electrolyte fuel cells with silica layers effectively improves catalyst durability by inhibiting not only particle aggregation but also the diffusion of dissolved metal species out of the catalysts. Coverage of supported precious metal photocatalysts with titania layers also enhances catalytic activity.     

负载贵金属光催化剂的光催化活性研究

在注入V离子的二氧化钛光催化剂上负载贵金属,制备了在可见光照射下具有高光催化活性的功能型光催化剂,研究在可见光和太阳光照射下丙炔的光催化水解反应，利用这些改性的二氧化钛构筑太阳能到化学能的转换系统.研究结果发现了V/Pt光催化剂在丙炔和水的光催化水解反应中，由于贵金属的存在，有利于促进发生加氢反应；导致丙烯的生成量增加.在可见光下的光催化活性也和负载贵金属所处的氧化状态有着密切的关系，贵金属完全被还原到0价是提高光催化活性的必要条件.     

贵金属负载光催化剂在丙炔光催化水解反应中的研究(Ⅲ)

利用三种不同负载方法制备了含有不同贵金属的TiO2光催化剂,通过测试其XPS和光催化活性和选择性发现,TiO2光催化剂在丙炔和水的光催化水解反应中,由于贵金属的存在,有利于促进发生加氢反应,导致丙烯的生成量增加.Pt,Ru,Rh,Pd和Ag负载在TiO2上,在紫外线照射下(λ>270nm),Pd负载的TiO2光催化剂表现出最高的光催化活性.光催化活性和负载贵金属所处的氧化状态有密切的关系,贵金属完全被还原到0价是提高光催化活性的必要条件.     

Recent advances in the determination of the platinum group elements and gold

Accurate determinations of the platinum group elements (PGEs) and gold, known as the precious metals, have always been difficult tasks. The metals are often present at trace levels in sample types of complex composition. This situation has improved recently due to developments of instrumental methods and their applications to analyses of the precious metals in a variety of matrices. Attention has been given to determinations of traces of precious metals in biological, clinical and environmental samples. Foremost in importance is inductively coupled plasma mass spectrometry (ICP-MS) which has provided a sensitive means of simultaneous determination of traces of PGEs and gold. Important extensions and improvements in atomic absorption spectrometry (AAS), nuclear and electrochemical methods have been reported also. More research on sample treatments, especially fire assays, applied to PGEs has been carried out. Chlorination has proven to be a viable alternative to fire assays for preconcentration of PGEs and gold in analyses of geological materials. In addition, the recent availability of some additional reference materials will be of great assistance in research work on precious metals.     

From Waste to Green Applications: The Use of Recovered Gold and Palladium in Catalysis

The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed.     

Iron-catalyzed C–H amination and its application in organic synthesis

Transition-metal-catalyzed direct C–H bond amination is an attractive strategy in preparation of nitrogen containing molecules which are common in naturally occurring and pharmaceutically important compounds. Comparing to the precious metals commonly used in this reaction, non-precious metals such as iron are abundant in earth, relatively low toxic, and more biocompatible, which meet the increasing demand for environmentally benign and sustainable chemical processes. In this review, we described the development in iron catalyzed C–H bond amination reactions from historical landmarks to recent achievements, and placed emphasis on their applications in organic synthesis, i.e. natural product synthesis and/or modification.     

The tin-collection scheme for the determination of platinum-group metals, gold and silver

A comprehensive analytical scheme is presented for the determination of the six platinum-group metals, gold and silver. It is the result of the integration of separate procedures that have been described previously, in part, over the course of several years. The analytical scheme has been thoroughly tested in umpire and standards work on a wide variety of materials and, as a consequence, is of increasing interest to many laboratories. The precious metals are collected in molten tin when the sample is fused at 1200-1250 degrees with a flux containing stannic oxide, sodium carbonate, silica, borax and flour. The resultant tin alloy is dissolved and the precious metals are isolated by ion-exchange, solvent extraction and/or distillation procedures. With the exception of the usual facilities required in the fusion step of fire assaying, standard equipment can be used in the wet-chemical operations for the isolation and determination of the individual precious metals.