Design of p–p heterojunctions based on CuO decorated WS2 nanosheets for sensitive NH3 gas sensing at room temperature

Tungsten disulfide (WS2) nanosheets (NSs) have become a promising room-temperature gas sensor candidate due to their inherent high surface-to-volume ratio, tunable electrical properties, and high on-state current density. For further practical applications of WS2-based gas sensors, it is still necessary to overcome the insensitive response and incomplete recovery at room temperature. In this work, we controllably synthesized high-performance ammonia (NH3) gas sensor based on CuO decorated WS2 NSs. The optimized p–p WS2/CuO heterojunctions improve the surface catalytic effect, thereby enhancing the gas-sensing performance. The pure WS2 NSs-based gas sensors showed a low response and an incomplete recovery in the case of NH3 sensing. After the functionalization of CuO nanoparticles, the WS2/CuO heterostructure-based gas sensor exhibits an improved response value of 40.5% to 5 ppm NH3 and full recoverability without any external assistance. Density functional theory calculations illustrate that the adsorption of CuO for NH3 is much superior to WS2. The p–p heterojunctions strategy demonstrated in this work has great potential in the design of sensitive materials for gas sensors, and provides useful guidance for enhancing the room-temperature sensitivity and recoverability.