High-Energy-Surface Engineered Metal Oxide Micro- and Nanocrystallites and Their Applications

Abstract

Because many physical and chemical processes occur at surfaces, surface atomic structure is a critical factor affecting the properties of materials. Due to the presence of high-density atomic steps and edges and abundant unsaturated coordination sites, micro- and nanocrystallites with high-energy surfaces usually exhibit greater reactivity than those with low-energy surfaces. However, high-energy crystal surfaces are usually lost during crystal growth as the total surface energy is minimized. Therefore, the selective exposure of high-energy facets at the surface of micro- and nanocrystallites is an important and challenging research topic. Metal oxides play important roles in surface-associated applications, including catalysis, gas sensing, luminescence, and antibiosis. The synthesis of metal oxide micro- and nanocrystallites with specific surfaces, particularly those with high surface energies, is more challenging than the synthesis of metal crystals due to the presence of strong metal-oxygen bonds and diverse crystal structures. In this Account, we briefly summarize recent progress in the surface-structure-controlled synthesis of several typical metal oxide micro- and nanocrystallites, including wurtzite ZnO, anatase TiO2, rutile SnO2, and rocksalt-type metal oxides. We also discuss the improvement of surface properties, focusing on high-energy surfaces. Because of the huge quantity and diverse structure of metal oxides, this Account is not intended to be comprehensive. Instead, we discuss salient features of metal oxide micro- and nanocrystallites using examples primarily from our group. We first discuss general strategies for tuning the surface structure of metal oxide micro- and nanocrystallites, presenting several typical examples. For each example, we describe the basic crystallographic characteristics as well as the thermodynamic (i.e., tuning surface energy) or kinetic (i.e., tuning reaction rates) strategies we have used to synthesize micro- and nanocrystallites with high surface energies. We discuss the structural features of the specific facets and analyze the basis for the enhanced performance of the metal oxide micro- and nanocrystallites in water splitting, the degradation of organic pollutants, gas sensing, catalysis, luminescence, and antibiosis. Finally, we note the future trends in high-energy-facet metal oxide micro- and nanocrystallite research. A comprehensive understanding of the properties of metal oxide micro- and nanocrystallites with high-energy crystal surfaces and related synthetic strategies will facilitate the rational design of functional nanomaterials with desired characteristics.

Polyhedral 30‐Faceted BiVO4 Microcrystals Predominantly Enclosed by High‐Index Planes Promoting Photocatalytic Water‐Splitting Activity

“…[1][2][3] High-index surfaces normally grow faster than lowindex ones and are usually lost during crystal growth due to minimization of the total surface energy. Although the selective exposure of high-index facets at the surface is an important and challenging research topic, much progress has been made in the formation of many kinds of relevant noble metal nanocrystals, which have been extensively applied in catalytic reactions, including those in fuel cells, [4] photocatalysis, [5][6][7] electrocatalysis, [8,9] and petroleum catalytic reforming.…”

Morphology evolution of NaTaO3 submicrometer single-crystals: from cubes to quasi-spheres

“…In the past decade, many efforts have been devoted to controlling the crystal surface structures for specific purpose, since many physicochemical properties of crystals strongly depend on their exposed surface [1][2][3][4][5]. Despite the great success in morphology-controlled syntheses of nanocrystals, our comprehension of the formation mechanism of specific surface of crystals in nanoscale is far from enough.…”

Facet‐Engineered Surface and Interface Design of Photocatalytic Materials

“…Kinetic control is another versatile approach to the thermodynamically disfavored surface facets 23. For instance, the exposed facets of Ag 2 O were tailored through altering the concentrations of starting materials 35.…”

“…The precisely controlled photocatalysts offer an ideal platform for investigating the dependence of photocatalytic performance on facets and the related mechanisms 23, 24, 25, 26. In this review, we focus on the recent advances in the facet‐engineered surface and interface design toward the photocatalysis applications.…”