Functions and Applications of Core–Shell Materials in Hydrogenation-Related Processes

Abstract

This chapter addresses recent advances on the core–shell catalysts in hydrogenation-related processes. In such catalysts, the shell is capable of protecting the active sites in the core from sintering or being poisoned. The shell pore size is capable of controlling the entrance and binding configuration of the reactant molecules with the active sites on the core, which is conducive to size-selective and regio-selective catalysis. The shell thickness influences the diffusion of the reactants/products and hence the product distribution. The core–shell catalysts show high versatility in water- or organic-phase hydrogenation reactions by properly adjusting the shell hydrophilicity. Aside from playing the role of active sites, the core is sometimes magnetic to facilitate catalyst separation or is made of comparatively inexpensive metals to geometrically or electronically promote the metal overlayer. In situ and operando techniques together with theoretical calculations reveal the dynamic compositional/structural changes of the core–shell catalysts. The applications of the elaborately designed core–shell materials in measuring the hydrogen spillover distance and as Raman signal enhancer are demonstrated. CO/CO2 methanation to CH4 is used to exemplify the advantages of the core–shell catalysts in high-temperature and exothermic hydrogenation reactions. Finally, the implications and challenges of the core–shell catalysts in hydrogenation reactions are discussed.