Catalysts future research issues

Many applications, especially in electrochemistry, rely on the use of expensive and rare metals, like Pt, Li, and rare-earth elements. In the synthesis of micro- and me-soporous materials, costly structure-directing agents are sometimes applied. The reduction of catalyst mass and the prevention of waste formation, for instance by recycling of synthesis additives, are therefore highly topical research issues. The practicability of future technologies based on catalysis will depend on the availability of efficient catalysts composed of abundant elements prepared by robust, preferentially aqueous-based synthesis methods and the reduction of environmental impacts arising from catalyst manufacture. 

The long-term stability of Pd-based electrocatalysts is one of the unavoidable issues for PEM fuel cell applications. Pd-Pt-based ORR catalysts are more stable than Pd-transition metal alloys under harsh fuel cell conditions, but may still not meet the long-term fuel cell operation requirement due to the Pd leaching out. Future research may focus on improving the durability of Pd-based catalysts by surface modification and composition optimization. Core-shell type of catalyst with Pd-based materials as the core and Pt as the shell may be one of the most promising candidates to be used in the automotive fuel cell due to its low Pt content and high activity and stability. 

After assessing the issues in the research, we propose several directions for future research. First, it is important to find the correlation between structure/composition of the catalyst and catalytic performance. More careful studies are needed in the future. Second, it is worthwhile to study the nature of active sites and reaction mechanisms on some of new catalysts. This can be done by in situ spectroscopic characterization of working catalysts, by conducting kinetic studies, and by isotopic... 

ImmobiUzation is and will be an important issue in the future. Much research has been focused on the use of simple insoluble polymeric systems as supports, but there have also been attempts to immobUize chiral catalysts via encapsulation. The chiral membrane reported by Vankelecom [122], and the microencapsidated chiral catalysts prepared by Kobayashi et al. [ 123] represent excellent examples of such variations, hi addition, the immobiUzation of catalysts using thin films was reported [ 14]. 

Several contributions and review papers have been published on the SCR processes on metal oxides however, there are still several points that deserve to be commented upon. In this chapter, we will first discuss some general aspects of SCR with special focus on some issues and questions that should be clarified regarding future prospects and new directions of research in this field, which is centred on the use of metal oxide catalysts. Then, a more detailed discussion regarding the type of catalysts and reaction mechanism will be made for the SCR-NH3 and the SCR-HC processes. 

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