Synthesis of Tin Dioxide Octahedral Nanoparticles with Exposed High‐Energy {221} Facets and Enhanced Gas‐Sensing Properties

Abstract

Tin dioxide (SnO 2 ), an n-type semiconductor with a wide band gap of 3.6 eV, has been widely used in photocatalytic degradation of organic dyes, [1] photovoltaic devices, [2] rechargeable lithium batteries, [3] and so on. In particular, remarkable receptivity to variations in gaseous environments and excellent chemical stability have made SnO 2 the bestknown gas-sensing material. [4][5][6][7][8][9] Over the past decades, considerable efforts have been made to improve the sensitivity and selectivity of SnO 2 -based solid-state gas sensors through modifying the sensing material itself and the fabrication technique, such as doping of catalytic metal particles, [4] hybridization of different sensing materials, [5, 6] and optimization of working temperature. [7] In principle, gas sensing by metal-oxide semiconductors like SnO 2 is based on the oxidation-reduction reaction of the detected gases occurring on the semiconductor surface, which leads to an abrupt change in conductance of the sensor. For this reason, the gas-sensing ability of metal oxide semiconductors is in theory very sensitive to the crystal faces of the sensing materials.[10] From the viewpoint of chemical activity, metaloxide nanocrystals with particular exposed crystal planes, such as high-index facets, may be good sensing materials, because high-index facets having high densities of atom steps, ledges, kinks, and dangling bonds usually exhibit much higher chemical activity. [11][12][13] However, such a strategy to improve sensitivity and selectivity of sensors has not attracted much attention up to now, possibly due to the difficulty of synthesizing metal-oxide nanocrystals with specific exposed crystal planes.Herein we report a simple method for the preparation of octahedron-shaped SnO 2 with exposed high-index {221} facets by exploiting the coordinative-adsorption effect of HCl and poly(vinyl pyrrolidone), PVP, in solution. The {221} facets of SnO 2 have a higher relative surface energy (2.28 J m À2 ) than common low-index facets such as {110} (1.401 J m À2 ), {101} (1.554 J m À2 ), and {100} (1.648 J m À2

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

“…[10] However, the generation of metal oxide micro-and nanocrystallites with high-index surfaces is comparatively more difficult due to the presence of strong metal-oxygen bonds and diverse crystal packing structures. [11] Only a few binary metal oxides, such as Co 3 O 4 , [12] anatase TiO 2 , [13][14][15] Fe 3 O 4 , [16] Cu 2 O, [17,18] and SnO 2 , [19] have been successfully achieved. Multinary metal oxide crystals are relatively more meaningful than binary ones because they not only possess more complex functions, but their properties also be readily adjusted by tuning the ratio of the component elements.…”

Two-Dimensional Zinc Oxide Nanostructures for Gas Sensor Applications

“…Indeed, theoretical and experimental results indicate that nanostructured materials with exposed crystal surfaces can exhibit special features in applications such as catalysts [25,26] and gas sensors [19,[27][28][29][30]. Han et al [31] showed that SnO 2 octahedral nanoparticles with exposed high energy {221} facets, exhibited better gas-sensing performance towards ethanol than those with mainly exposed {110} facets. Similarly, in another work [32], they reported that monodisperse WO 3 nanoparticles with a higher percentage of (010) exposed facets exhibited better gas sensing of 1-butylamine than nanoparticles with (001) and (100) exposed facets.…”

First Principles Analysis of H2O Adsorption on the (110) Surfaces of SnO2, TiO2 and Their Solid Solutions

“…26 Its sensitivity and selectivity depend also on the exposed facets of the rutile crystal structure. 27 Han et al 28 synthesized SnO 2 particles with different morphology and found that octahedral particles with 3 exposed high-energy (221) facets show highest gas-sensing performance towards ethanol.…”

“…Furthermore, such high-index (221) facets have a higher surface energy 28 and thus are more difficult to produce than spontaneously growing low-index facets 30 .…”