Electrochemical promotion of nanostructured catalysts and electrocatalysts for environmentally important processes

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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.