Electrochemical promotion of nanostructured catalysts and electrocatalysts for environmentally important processes

近几十年来，世界见证了能源需求和基于化石燃料（主要是石油、天然气和煤炭）的消费品材料生产的指数增长。由于不可能减少人类活动，因此全球能源需求不断增长，因此显然需要改变游戏规则的战略，以实施基于可再生原料的替代能源以及用于温室气体排放的封存和回收的替代方法。 现代多相催化剂，用于增强化学反应和显着降低能源需求的强大的纳米结构系统，提供了出色的机会。典型的多相催化剂由沉积在高表面积载体上的纳米级金属或金属氧化物颗粒组成。催化剂经常遭受失活或低催化活性。（i）化学促进：在制备过程中向催化剂中加入化学物质，例如，K、Na、Ce、Sn等，以改善其催化性能，并且通常改善其稳定性和寿命。添加这样的物质改变了催化剂的电子或晶体结构，从而改善了所需化学反应的催化性能和选择性。 (ii)金属-载体相互作用（MSI），定义为载体在改变催化剂性质方面起关键作用的效应，这是两种材料之间相互作用的结果，通常导致更高的催化活性;（iii）电化学促进催化（EPOC）或也称为催化活性的非法拉第电化学改性（NEMCA）是30年前发现的，是增强催化活性的替代方法。EPOC引入了一类新的促进剂，以前在多相催化中是未知的，例如，O2-、H+、K+、Na+、OH-等。通过在催化剂工作电极和沉积在固体电解质上的对电极之间施加电流或电势，由于催化剂的电子性质的改变，可以显著改变催化活性和选择性。 众所周知，上述三种现象之间存在着操作上的区别，而不是功能上的区别。尽管化学促进和MSI在操作条件下难以控制，但EPOC现象提供了对表面上促进剂的量的原位控制，并提供了通过施加小电流或电势来改变催化剂性质的独特机会。 尽管EPOC已经研究了30多年，并应用于100多种具有各种电解质、催化剂和反应的催化体系，但仍存在一些重要的问题和应用，需要解决：（i）观察具有高度分散的纳米颗粒催化剂的电化学促进的反应条件和电化学电池设计是什么？(ii)离子导电载体上的纳米粒子的“自诱导”或“无线”促进机制是什么及其与MSI的关系？(iii)EPOC现象在质子或阴离子导体电催化氧化复杂有机燃料中的应用有哪些新途径？ 拟议的研究计划的长期目标是建立一个全面的理解EPOC与纳米结构的催化剂支持离子导电陶瓷和质子（阴离子）交换聚合物电解质。在纳米颗粒尺度上对EPOC和MSE之间的关系进行基本理解，以合理设计燃料电池的高效催化系统，并减少固定和汽车源的温室气体。

In recent decades, the world has witnessed an exponential increase in energy demand and consumer product materials production based on fossil fuels, mainly oil, gas and coal. Because it is not possible to decrease the human activity and therefore the growing global energy demand it is evident that the game-changing strategies are required to implement the alternative energy sources based on renewable feedstocks as well as the alternative approaches for sequestration and recycling of greenhouse gas emissions. Modern heterogeneous catalysts, powerful nanostructured systems used to enhance chemical reactions and significantly reducing energy demand, offer outstanding opportunities. A typical heterogeneous catalyst consists of a nanosized metal or metal oxide particle deposited on the high surface area supports. Catalysts often suffer from deactivation or low catalytic activity. Therefore, various promoting routes are used: (i) Chemical promotion: addition of chemical species to the catalyst during preparation, e.g., K, Na, Ce, Sn, etc., to improve its catalytic behavior and often its stability and a life-span. The addition of such species changes the electronic or crystal structure of the catalyst, thus improving catalytic performance and selectivity for the desired chemical reaction. (ii) Metal-support interaction (MSI) defined as the effect where the support plays a key role in changing the properties of the catalyst as a result of the interaction between the two materials, usually resulting in higher catalytic activity; (iii) Electrochemical promotion of catalysis (EPOC) or also referred to as non-Faradaic electrochemical modification of catalytic activity (NEMCA) was discovered 30 years ago and is an alternative approach to enhance catalytic activity. EPOC introduced a new class of promoters previously unknown in heterogeneous catalysis, e.g., O2-, H+, K+, Na+, OH-, etc. By applying electrical current or potential between the catalyst-working electrode and a counter electrode deposited on a solid electrolyte, catalytic activity and selectivity can be significantly altered due to modifications of electronic properties of the catalyst. It is well established that an operational and not a functional difference between the above three phenomena exists. Whereas chemical promotion and MSI are difficult to control under operating conditions, the EPOC phenomenon offers in-situ control of the amount of promoters on surfaces and offers a unique opportunity to modify catalyst properties via application of small electrical current or potential. Despite that EPOC has been investigated for more than 30 years and applied for over 100 catalytic systems with various electrolytes, catalysts and reactions, several important issues and applications remain and need to be addressed: (i) What are the reaction conditions and the electrochemical cell design to observe electrochemical promotion with highly dispersed nanoparticle catalysts? (ii) What is the mechanism of the “self-induced” or “wireless” promotion with NPs supported on ionically conductive supports and its relationship to MSI? (iii) What are new approaches for application of EPOC phenomenon in electocatalysis for oxidation of complex organic fuels using proton or anion conductors? The long-term objectives of the proposed research program are to establish a comprehensive understanding of the EPOC with nanostructured catalysts supported on ionically conductive ceramics and proton (anion) exchange polymer electrolytes. To develop a fundamental understanding and a relationship between EPOC and MSE at the nanoparticle scale for the rational design of the efficient catalytic systems for fuel cells and abatement of greenhouse gas from the stationary and automobile sources.