Tuning Activities of K_1.9Na_0.1Ta₂O₆·2H₂O Nanocrystals in Photocatalysis by Controlling Exposed Facets

Abstract

Morphology-controlled synthesis of tantalates is a major challenge in the field of material science. Herein, an innovative strategy has been developed for controllably synthesizing K1.9Na0.1Ta2O6·2H2O (KNTO) nanocrystals shaped as octahedra and nanosheets without using any capping agents. The obtained nanocrystals show high activity in photocatalytic H2 evolution from CH3OH/H2O solution, and their performance closely depends on the exposed facets, in which the {111}-facet-bounded nanooctahedra exhibit more than 3 times higher activity than the nanosheets dominated with {101} facets. The influence of surface atomic structure and electronic band structure on the photocatalytic properties of the KNTO nanocrystals is systematically studied. This is the first report for the facet controllable synthesis of tantalate materials with highly regular shapes. The present approach is anticipated as a general strategy for controllable synthesis of tantalate materials and also provides feasibility for rational design and activity optimization of shape-controlled photocatalysts for H2 production.

Perovskite nanostructures assembled in molten salt based on halogen anions KX (X = F, Cl and Br): Regulated morphology and defect-mediated photocatalytic activity

“…Various synthetic methods have been proposed for synthesis and morphology evolution of CaCu 3 Ti 4 O 12 such as solid-state reaction, sol-gel synthesis and co-precipitation etc., though proved to be undesirable since as-obtained sample suffers from phase impurity and low surface area [19][20][21]. In contrast to these techniques, molten salt synthesis is known as a booming, cost-effective and feasible approach aiming at surface modification and morphology controlled synthesis [12,[22][23][24]. This environmentally friendly synthetic method had been applied to the fabrication of wide range of perovskites, i., K 1.9 Na 0.1 Ta 2 O 6 , Bi 4 Ti 3 O 12 , SrBi 2 Ta 2 O 9 and Pb 2 Bi 4 Ti 5 O 18 , etc., for their diverse applications [22][23][24][25].…”

“…In contrast to these techniques, molten salt synthesis is known as a booming, cost-effective and feasible approach aiming at surface modification and morphology controlled synthesis [12,[22][23][24]. This environmentally friendly synthetic method had been applied to the fabrication of wide range of perovskites, i., K 1.9 Na 0.1 Ta 2 O 6 , Bi 4 Ti 3 O 12 , SrBi 2 Ta 2 O 9 and Pb 2 Bi 4 Ti 5 O 18 , etc., for their diverse applications [22][23][24][25]. Very recently, taking advantages of the process by stepwise ionization of molten salts, a comprehensive study on morphology tailoring and visible light photocatalytic activity of CaCu 3 Ti 4 O 12 was investigated [12].…”

Facet‐Dependent Optical Properties of Semiconductor Nanocrystals

“…Ag 2 O cubes have the best photocatalytic activity, whereas rhombic dodecahedra have the lowest activity. In the literature, surface energy and molecular interactions with crystal surfaces through electrostatic considerations, as well as surface atomic arrangements and trap states/defects within a crystal, have been proposed to explain the observed facet‐dependent photocatalytic activities . The example of Cu 2 O and Ag 2 O having an identical crystal structure but exactly opposite photocatalytic behaviors demonstrates that these explanations are likely incorrect because they cannot be broadly applied.…”

Crystal facet tailoring arts in perovskite oxides

“…72 Wang et al synthesized octahedra and nanosheets of tantalate K 1.9 Na 0.1 Ta 2 O 6 •2H 2 O and the {111}-facet-bound nanooctahedra show more than 3 times higher photocatalytic water splitting activity than the nanosheets dominated by {101} facets. 73 Nearly cubic shaped AgNbO 3 micrometer sized crystals could be prepared by hydrothermal treatment of NH 4 HF 2 , Ag 2 O, and Nb 2 O 5 raw chemicals. 74 The most stable phase of AgNbO 3 at room temperature is orthorhombic with the space group Pmc2 1 .…”

“…80 Wang et al reported a method to controllably synthesize mixed K, Na doped crystals of K 1.9 Na 0.1 Ta 2 O 6 •2H 2 O (KNTO) with octahedra (enclosed by {111} facets) and nanosheets (dominated by {101} facets) shapes, and the octahedra exhibit more than 3 times higher activity in photocatalytic H 2 evolution from CH 3 OH/ H 2 O solution than that of nanosheet samples. 81 Gu et al used different additives of polyethylene glycol (PEG) to prepare KTa 1−x Nb x O 3 via the hydrothermal method at 200 °C. 82 KTaO 3 nano-octahedra could be prepared with mainly exposed facets of {111} because they are crystalized into the Pm3 ˉm space group (Fig.…”