Microwave-induced plasma promoted dielectric heating: metrology and application to the photocatalytic activation of water

微波诱导等离子体促进介电加热：计量学及其在水光催化活化中的应用

• 批准号: EP/E018262/1
• 负责人: Rik Brydson
• 金额: $ 33.67万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE018262%2F1
• 关键词: Microwave; induced; plasma; promoted; dielectric

There is a clear and effective need for the synthesis of new materials that can sustain and develop future technologies and underpin modern society. To increase the diversity of materials accessible it is necessary to develop new synthetic techniques. The proposed research describes the application of microwave radiation to provide energy to drive chemical reactions between solids and/or between solids and gases. A confined gas when exposed to microwave radiation can ionise giving rise to a microwave-induced plasma (MIP) that can be used to provide heat to drive reaction between bulk solids and as a source of reactive gas species that can chemically modify a material. Many polar liquids (e.g. water) and some solids do interact directly with microwaves causing rapid heating and reaction, but many technologically important materials are transparent to microwaves at room temperature thus preventing use in reactions. However, direct microwave (dielectric) heating is temperature dependent and many materials will directly couple with microwaves at elevated temperatures. Unfortunately quantitative data enumerating the temperature dependence of dielectric heating for most solids is not currently available. We propose to synthesise new compounds and composite materials using a combination of MIP and dielectric heating that will be supported by measurements (metrology) of the temperature dependence of dielectric heating of precursor and product materials. The heat provided by the MIP will cause many solids that are microwave transparent at room temperature to exhibit significant dielectric heating at elevated temperatures. Initially MIP promoted dielectric heating will be identified for materials by monitoring the temperature of a reaction mixture in situ, where rapid temperature rises and sample temperatures in excess of the plasma temperature will indicate significant dielectric heating. Materials that exhibit strong temperature dependence will then be measured more rigorously and this information used to correlate the structure and morphology of reaction products and direct subsequent synthetic reactions. The temperature dependence of microwave heating will allow differential heating to be exploited, where in a heterogeneous mixture, different solids can be simultaneously heated to different temperatures. This is in direct contrast to traditional conduction/convection heating methods where a solid mixture is heated uniformly.The solids we will target are semiconducing catalysts relevant to the photocatalytic activation of water that generate hydrogen from solar energy. Hydrogen is a clean energy resource because the combustion product is water and therefore photocatalysis represents an opportunity to meet the increasing energy demands of society and also potentially replace limited fossil fuel resources that are detrimental to the environment. Photocatalysts typically comprise a heterogeneous composite of semiconducting metal oxide and metal particles/metal rich regions that will exhibit markedly different temperature dependence with respect to microwave heating giving rise to differential heating. A combination of differential heating and reactive MIPs therefore provides additional opportunity for novel materials synthesis by selective modification from reaction between a MIP and heated component. Furthermore, reactive MIP can be used to modify a solid to alter the dielectric properties to either increase or decrease the extent of dielectric heating.MIP promoted dielectric heating represents a distinct and adventurous synthetic method for the preparation of new materials. Metrology and rigorous characterisation of materials using a range of microscopy and other techniques will underpin exploratory synthetic work to realise the potential of this novel method.

对于能够维持和发展未来技术并支撑现代社会的新材料的合成，存在着明确而有效的需求。为了增加可获得材料的多样性，有必要开发新的合成技术。拟议的研究描述了微波辐射的应用，以提供能量来驱动固体之间和/或固体与气体之间的化学反应。当暴露于微波辐射时，受限气体可以电离，从而产生微波诱导等离子体（MIP），其可以用于提供热量以驱动散装固体之间的反应，并且作为可以化学改性材料的反应性气体物质的来源。许多极性液体（如水）和一些固体直接与微波相互作用，导致快速加热和反应，但许多技术上重要的材料在室温下对微波是透明的，因此无法用于反应。然而，直接微波（电介质）加热是温度依赖性的，许多材料将在高温下直接与微波耦合。不幸的是，目前还没有关于大多数固体介电加热温度依赖性的定量数据。我们建议使用MIP和介电加热的组合来合成新的化合物和复合材料，这将由前体和产品材料的介电加热的温度依赖性的测量（计量学）来支持。由MIP提供的热量将导致许多在室温下微波透明的固体在升高的温度下表现出显著的介电加热。最初，MIP促进的介电加热将通过原位监测反应混合物的温度来识别材料，其中快速温度升高和超过等离子体温度的样品温度将指示显著的介电加热。表现出强烈温度依赖性的材料将被更严格地测量，这些信息用于关联反应产物的结构和形态，并指导随后的合成反应。微波加热的温度依赖性将允许利用差异加热，其中在非均质混合物中，不同的固体可以同时加热到不同的温度。这与传统的传导/对流加热方法形成了鲜明对比，传统的传导/对流加热方法是均匀加热固体混合物。我们的目标是与水的光催化活化相关的固体催化剂，这些催化剂可以从太阳能中产生氢气。氢气是一种清洁能源，因为燃烧产物是水，因此氢气代表了满足社会日益增长的能源需求的机会，并且还可能取代对环境有害的有限化石燃料资源。光催化剂通常包括半导体金属氧化物和金属颗粒/富含金属的区域的非均相复合物，其将表现出相对于微波加热的显著不同的温度依赖性，从而引起差热。因此，差热和反应性MIP的组合通过MIP和加热组分之间的反应的选择性改性为新型材料合成提供了额外的机会。此外，反应性MIP可用于改性固体以改变介电性质，从而增加或减少介电加热的程度。MIP促进的介电加热代表了用于制备新材料的独特且冒险的合成方法。使用一系列显微镜和其他技术对材料进行计量和严格表征将支持探索性合成工作，以实现这种新方法的潜力。

项目成果

Electron Microscopy of Cocatalyst Nanostructures on Semiconductor Photocatalysts

• DOI: 10.1002/cctc.201000443
• 发表时间: 2011-06
• 期刊: ChemCatChem
• 影响因子: 4.5
• 作者: N. Hondow;Y. Chou;K. Sader;R. Douthwaite;R. Brydson

Microwave Synthesis Using Microwave Transparent Metal Oxides: Plasma-Promoted Dielectric Heating

使用微波透明金属氧化物的微波合成：等离子体促进介电加热

• 发表时间: 2010
• 期刊: A European Journal
• 作者: N/a Chou

v: The Role of Ion Migration and Alloy Formation on the Stability of Core Shell Cocatalysts for Photoinduced Water Splitting

• DOI: 10.1021/jp108974s
• 发表时间: 2010-12
• 期刊: Journal of Physical Chemistry C
• 影响因子: 3.7
• 作者: N. Hondow;Y. Chou;K. Sader;R. Brydson;R. Douthwaite