Experimental and theoretical studies of V_2O_5@TiO_2 core-shell hybrid composites with high gas sensing performance towards ammonia

摘要

This study reports a facile but efficient synthesis method for the preparation of titanium oxide coated vanadium oxide (V_2O_5@TiO_2) core-shell nanostructures in water bath at mild temperatures (≤100°C). This method is featured as short reaction time, no requirement of high temperature calcination (>500 °C) for TiO_2 crystallization, easily tunable TiO_2 shell thickness, high yield, and good reproducibility. The asprepared V_2O_5@TiO_2 nanocomposites can exhibit a large surface area, and good stability. The gas-sensing properties of V_2O_5@TiO_2 core-shell nanoparticles were investigated, it was found that the core-shell materials exhibit superior sensing performance (high response, good selectivity, and short response time) toward ammonia than pure TiO_2 or V_2O_5 sensor materials. Besides experimental studies, theoretical simulations using Density Functional Theory (DFT) method were conducted to fundamentally understand the adsorption behavior of different target gases, such as ammonia, ethanol, methanol, acetone and n-butylamine on the anatase TiO_2 (101) surface. The results show that the ammonia is of the lowest adsorption energy (-1.04eV), which can help explain why the V_2O_5@TiO_2 core-shell sensor exhibits excellent response toward ammonia. These findings may bring a new insight into the designing of TiO_2-based nanocomposites with diverse functions; meanwhile, provide a better understanding on interactions, at atomic scale, between the TiO_2 crystalline surface and the reducing gases.