Multi-interfacial NiO@In2O3/ZnO porous heterojunction arrays with engineered d-band center and charge transfer for efficient visible-light activated ammonia detection at room temperature

A multi-interfacial NiO@In 2 O 3 /ZnO porous heterojunction array was designed. • The heterojunction array enabled highly efficient room temperature ammonia detection. • Multi-phase interfaces greatly enhanced the ammonia adsorption and charge transfer. • Porous array design and light activation further promoted the sensing reaction. • The work clarified the important role of multi-phase interfaces in gas sensing. Heterojunction engineering provides an effective means to enhance the gas sensing performance of metal oxide semiconductors through band structure optimization and interface effects. However, current research on heterojunction engineering primarily centers on binary heterojunctions (including p-n, n-n, and p-p junctions), while studies concerning ternary or multicomponent metal oxide heterojunctions for gas sensing remain exceedingly limited and challenging. Herein, a ternary NiO@In 2 O 3 /ZnO porous heterojunction array is fabricated in-situ on commercial alumina sensing substrate via a facile liquid-phase chemical reaction combined with topotactic transformation. The heterojunction array enables highly efficient room temperature ammonia detection under visible light illumination, exhibiting a high response of 263% towards 100 ppm ammonia, a fast recovery of 21 s, and a low detection limit of 0.483 ppm. Moreover, it displays excellent selectivity, strong resistance to humidity interference, and stable long-term performance. First-principles calculations integrated with spectroscopic characterization suggest that the construction of ternary NiO@In 2 O 3 /ZnO heterojunction with multi-phase interfaces greatly enhances the ammonia surface adsorption and promotes the interfacial charge transfer efficiency. Interestingly, there exists a notable positive correlation between the d-band center position of sensing materials and their adsorption behavior as well as sensing performance. This work not only achieves a multi-dimensional enhancement in the room temperature ammonia sensing performance of metal oxide semiconductors through ternary heterojunction construction, porous array design and external light field activation, but also significantly enhances the gas sensing mechanism of ternary heterojunctions at atomic and electronic scale, offering new insights for the rational designing of high-performance resistive gas sensors via multi-phase interfaces.