Electrochemical promotion is an exciting area of catalysis that investigates the role of spillover species on the catalytic properties of a metal catalyst interfaced with a ionic or mixed ionic-electronic conducting support. Heterogeneous catalysis can benefit by the understanding of EPOC and catalyst-support interactions that would allow the development of ‘tunable’ catalysts. Our interest in EPOC is to investigate the mechanism of promotion by using novel reactor configurations, model catalysts and by studying the role of surface impurities on the catalytic and spillover processes.
The non-Faradaic electrochemical modification of catalytic is based on the modification of the chemisorption properties of the catalyst, by an applied potential, as a consequence of the electrochemical pumping of ions (promoters) from a solid electrolyte to the catalyst film. This phenomenon allows improving the catalytic performance of a metal catalyst in a very pronounced and controlled way.
Our interest is in using a novel system-configuration that consists of a mixed conducting support in the form of a dense pellet upon which a Pt catalyst film is deposited. By using a mixed ionic-electronic conducting support we eliminate the need for an external circuit (and electrochemical equipment) by internally short-circuiting the system. A dual chamber membrane reactor is used and while the reaction takes place in the reaction chamber, the supply of the promoting ions can be controlled by the use of an appropriate gas in the sweep chamber of the reactor.
|This project investigates the effect of impurities on the catalytic and electrocatalytic behaviour of systems known to exhibit EPOC. Impurities, originating from the catalyst preparation, or deposited on the catalyst surface during operation can have a very significant effect on the catalytic system. However, the role of impurities in EPOC has not yet been studied in detail and indeed the role of impurities is not fully understood. Therefore, a systematic study on the effect of impurities is necessary to fully assess their effect on a catalyst system (in this case Pt/YSZ). This work involves the introduction of known amounts and types of surface species (impurities) on the catalyst systems and the study of their effect on the system (both under catalytic and electrocatalytic conditions).|
|In addition the types and quantities of impurities on commercial catalysts are identified and their EPOC behaviour is compared.|
The focus of this project is the study of EPOC on model catalyst/electrodes. It is postulated that electrochemical promotion is due to the catalytically promoting action of ionic species that migrate (spillover) onto the catalyst surface under the influence of the applied potential. Spillover processes can be influenced by electrode impurities and morphology that are often related to the type of electrode used and electrode preparation method (porous or dense).In this work, dense micro-structured electrodes of precisely controlled geometry are used as the model catalyst. The electrodes (with patterns in finger-like form of different width length scales) are fabricated by sputtering and photolithography.
|This increases the three phase boundary (tpb) length available for electrochemical reactions for samples of decreasing feature-length-scale and is therefore expected to affect the spillover processes taking place under polarisation. This work is part of a collaborative project between Newcastle University and the University of Manchester. The team has combined expertise in micro-fabrication, development of high sensitivity analytical equipment, kinetic analysis and modelling of spillover phenomena.|