Synthesis of Ni-Induced Nb ₂ O ₅ /NiNb ₂ O ₆ n–n Heterojunction Nanowires for Ultrafast Room-Temperature Hydrogen Sensing via Interfacial Electron Modulation

The development of hydrogen (H 2 ) gas sensors with high sensitivity at room temperature remains a challenge. In this work, Nb 2 O 5 /NiNb 2 O 6 heterojunction nanowires with efficient H 2 gas-sensing performance were successfully synthesized via a hydrothermal and calcination method. Results from X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) experiments demonstrated that nickel was uniformly distributed within the Nb 2 O 5 lattice in the form of Ni 2+ . Scanning electron microscopy (SEM) observations revealed that Ni doping led to significant optimization of the composite’s nanowire structure. The sensor based on Nb 2 O 5 /NiNb 2 O 6 heterojunction nanowires exhibited a response value of up to 13.35–5000 ppm of H 2 at room temperature, with rapid response/recovery times (6/36 s), and the calculated lower limit of detection (LOD) was as low as 0.65 ppm. The excellent gas-sensing properties can be attributed to the creation of NiNb 2 O 6 by Ni doping, which sequentially induces the formation of an n–n heterojunction between Nb 2 O 5 and NiNb 2 O 6, enhancing the surface depletion effect and amplifying the resistive response signal. This study proposes a material design approach for developing low-power sensors suitable for monitoring high-risk hydrogen concentrations at room temperature, demonstrating significant potential in hydrogen storage and transportation safety as well as industrial leakage early warning systems.