Utilization of shape-controlled nanoparticles as catalysts with enhanced activity and selectivity
Shape-controlled nanoparticles with well-defined facets can be used as heterogeneous catalysts with enhanced activity and selectivity. The surface crystalline structure has a significant effect on the surface reaction, and shape control can be a way to obtain a desirable surface structure to improve the catalytic properties of nanoparticles. The shape of the nanoparticle can be formed by controlling the nucleation and overgrowth steps. Surface-capping agents are typically used to prevent aggregation of the nanoparticles during the overgrowth, but the subsequent treatment for their removal should be performed carefully. The extent of surface cleanness and the type of organic remnant can yield different catalytic properties. The surface agents, however, can also contribute to modulating the electronic structure or oxidation state of the surface, inducing improved catalytic activity and durability. Examples showing enhancements in the activity and selectivity of shape-controlled nanoparticles with well-defined facets are presented in this review, including electrocatalytic reactions, coupling reactions of organic compounds, water-gas shift reactions, CO oxidation, reforming reactions, and photocatalytic reactions. The well-defined facets control the adsorption of reactants to the surface, bond cleavage at the surface, desorption of products from the surface, and degree of surface-poisoning, resulting in enhanced activity and selectivity. However, the issues of shape preservation and mass production should be addressed further to apply the shaped nanoparticles in practical applications.