Editors: | Vayenas Intl. Symp. / Physical Chemistry and its applications for sustainable development Edited by: F. Kongoli, E. Aifantis, C. Cavalca, A. de Lucas Consuegra, A. Efstathiou, M. Fardis, D. Grigoriou, A. Lemonidou, S.G. Neophytides, Y. Roman, M. Stoukides, M. Sullivan, P. Vernoux, X. Verykios, I. Yentekakis |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2019 |
Pages: | 249 pages |
ISBN: | 978-1-989820-09-4 |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Hydrogen is a very important feedstock in the industry and a promising energy carrier with a main application in internal combustion engines and in fuel cell technology, as a clean and efficient alternative to the massive consumption of fossil fuels. Among the different methods for hydrogen production, catalytic routes are the most interesting ones, for instance via reforming and partial oxidation of hydrocarbons and biomass. In this sense, the addition of electronic promoters chemically (chemical promotion) or electrochemically (electrochemical promotion or EPOC) induces very significant and similar effects on catalytic hydrogen production reactions [1]. Both kinds of promotional phenomena follow the same general mechanism but the usefulness of the latter is highlighted. Hence the EPOC effect is based on the modification of the chemisorption properties of a metal catalyst by the electrochemical migration of promoter ions from a solid electrolyte support (via application of an electric current or potential) [2-3]. Hence, while in chemical promotion, a specific amount of a promoter is added during the preparation step of the catalyst. In the case of the electrochemical promotion, promoter ions are electrochemically pumped between the metal catalyst and the solid electrolyte in a controlled and reversible way during the reaction step [3]. Then, the electrochemical promotion presents several additional advantages, such as the possibility of optimizing the promoter coverage on the catalyst surface at different reaction conditions and the in-situ enhancement of the catalytic activity and selectivity. In this communication, the most important and recent contributions of our group in the electrochemical promotion of different hydrogen production reactions are reviewed. The functional similarities and operational differences between both promotion ways are pointed out, and their impact on the hydrogen production technology is discussed. By this method, the EPOC effects have shown a great interest in H2 production technology by improving catalytic activity and selectivity under working reaction conditions. In addition, the in-situ catalyst regeneration from carbon deposition, and the possibility of applying the EPOC in the field of H2 storage, among other novel contributions, lead EPOC to new opportunities in the H2 technology. For these purposes, novel catalyst films were developed by means of different preparation techniques and also by means of operando surface analysis techniques such as in-situ near-ambient pressure photoemission (NAPP) spectroscopy have been used in order to investigate the origin and mechanism of this phenomenon.