Chapter 12 - Nanocrystal Catalysts of High-Energy Surface and Activity

Abstract

Abstract Metal and metal oxide nanocrystals (NCs) enclosed by high-surface-energy facets (or high-energy surface) have attained enormous attention. The NCs of high-energy surface are thermodynamically unstable in their growth, resulting in a big challenge in the shape-controlled synthesis. To achieve this purpose, the indispensable kinetic control by electrochemical method or surfactant-based wet chemical route is widely exploited. Currently, high-energy surface monometallic NCs, such as Pt and Pd, and bimetallic NCs (surface decoration, alloy, and core-shell structure) are successfully synthesized. These metal NCs of uniform single crystallographic form as tetrahexahedron (THH), trapezohedron (TPH), hexoctahedron (HOH), or their concave morphology exhibit a remarkable performance in heterogeneous catalysis, electrocatalysis, and analysis. Apart from metal NCs, metal oxide NCs enclosed with high-surface-energy facets, such as TiO2 and BiVO4, present also an extensive application in photocatalysis, that is, water-splitting and dye-sensitized solar cells. The catalytic activity of NCs enclosed with high-energy facets possessing a high density of active sites is greatly enhanced compared with NCs enclosed with low-energy facets. More importantly, the NCs enclosed with high-energy facets provide a promising platform to fundamentally understand the principles in surface science and heterogeneous catalysis, shedding therefore new light on the rational design of practical catalysts with high activity, selectivity, and durability for energy conversion and storage. Future opportunity and challenge of NC catalysts of high-energy surface may consist in the fundamental understanding of surface structure-catalytic functionality of NCs in different catalytic environments and the development of synthesis technology to reach a rational design and mass production of supported NC catalysts with adjustable high-energy surface structure, controllable particle size, diversified substrate, and variable loadings for realistic applications.