Achieving highly-efficient H ₂S gas sensor by flower-like SnO ₂–SnO/porous GaN heterojunction

A flower-like SnO ₂–SnO/porous GaN (FSS/PGaN) heterojunction was fabricated for the first time via a facile spraying process, and the whole process also involved hydrothermal preparation of FSS and electrochemical wet etching of GaN, and SnO ₂–SnO composites with p–n junctions were loaded onto PGaN surface directly applied to H ₂S sensor. Meanwhile, the excellent transport capability of heterojunction between FSS and PGaN facilitates electron transfer, that is, a response time as short as 65 s and a release time up to 27 s can be achieved merely at 150 °C under 50 ppm H ₂S concentration, which has laid a reasonable theoretical and experimental foundation for the subsequent PGaN-based heterojunction gas sensor. The lowering working temperature and high sensitivity (23.5 at 200 ppm H ₂S) are attributed to the structure of PGaN itself and the heterojunction between SnO ₂–SnO and PGaN. In addition, the as-obtained sensor showed ultra-high test stability. The simple design strategy of FSS/PGaN-based H ₂S sensor highlights its potential in various applications.