Nano-porous hollow Li0.5La0.5TiO3 spheres and electronic structure modulation for ultra-fast H2S detection

Ultra-fast detection of hazardous gases with high selectivity is important for environmental safety monitoring. In this study, we report a Li0.5La0.5TiO3 (LLTO) sensor with an ultrafast response to H2S. We used a simple solvothermal method to controllably synthesize hollow LLTO nano-spheres. The LLTO nano-spheres had a porous surface structure, which provides sufficient channels for diffusion of H2S gas. Response/recovery speeds of 0.7 s/0.8 s were achieved at an optimum working temperature of 340 °C. To further improve the response, the band structure was modulated by Fe doping (FLTO). When doped with Fe3+, more oxygen vacancies were generated which enhanced the chemical absorption of O2 and generation of active oxygen species (O− and O2−). Furthermore, the band gap was also narrowed and the conduction band was elevated by 0.44 eV, which promoted charge transfer from the conduction band of FLTO to chemisorbed gas molecules. After doping, the response was 5.5 times as great as that of the pristine LLTO sensor for 30 ppm H2S and the optimum temperature decreased to 300 °C. In addition, the detection limit was as low as 100 ppb. The doped LLTO sensor also had good repeatability and long-term stability.

高选择性的超快速有害气体检测对环境安全监测至关重要。在本研究中，我们报道了一种对硫化氢（H₂S）具有超快响应的Li₀.₅La₀.₅TiO₃（LLTO）传感器。我们采用一种简单的溶剂热法可控地合成了中空LLTO纳米球。LLTO纳米球具有多孔表面结构，这为硫化氢气体的扩散提供了充足的通道。在340°C的最佳工作温度下，实现了0.7秒/0.8秒的响应/恢复速度。为了进一步提高响应，通过铁（Fe）掺杂（FLTO）对能带结构进行了调制。当掺杂Fe³⁺时，产生了更多的氧空位，这增强了O₂的化学吸附以及活性氧物质（O⁻和O₂⁻）的产生。此外，带隙也变窄，导带升高了0.44 eV，这促进了电荷从FLTO的导带向化学吸附的气体分子转移。掺杂后，对于30 ppm的H₂S，其响应是原始LLTO传感器的5.5倍，并且最佳温度降至300°C。此外，检测限低至100 ppb。掺杂的LLTO传感器还具有良好的重复性和长期稳定性。