Experimental and theoretical studies of V2O5@TiO2 core-shell hybrid composites with high gas sensing performance towards ammonia

- V2O5@TiO2 core-shell composites were prepared by coating TiO2 on V2O5 nanoparticles via a simple sol-gel method.
- The V2O5@TiO2 core-shell structure shows excellent response and selectivity to ammonia.
- DFT simulation was used to study the sensing mechanism towards ammonia.

This study reports a facile but efficient synthesis method for the preparation of titanium oxide coated vanadium oxide (V2O5@TiO2) 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 TiO2 crystallization, easily tunable TiO2 shell thickness, high yield, and good reproducibility. The as-prepared V2O5@TiO2 nanocomposites can exhibit a large surface area, and good stability. The gas-sensing properties of V2O5@TiO2 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 TiO2 or V2O5 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 TiO2 (101) surface. The results show that the ammonia is of the lowest adsorption energy (−1.04 eV), which can help explain why the V2O5@TiO2 core-shell sensor exhibits excellent response toward ammonia. These findings may bring a new insight into the designing of TiO2-based nanocomposites with diverse functions; meanwhile, provide a better understanding on interactions, at atomic scale, between the TiO2 crystalline surface and the reducing gases.