Morphological Exploration of NiO Derived from Metal–Organic Frameworks with PdO for Hydrogen Gas Sensor

As a promising clean-energy carrier, hydrogen requires highly sensitive and stable detection systems to ensure safety during its production, transportation, and storage. This paper presents the development of PdO-NiO composite gas sensors derived from metal–organic frameworks (MOFs) with controlled morphologies and p–p heterojunction structures. The PdO-NiO composites were synthesized via an MOF-derived method and calcined at varying temperatures to tailor their morphology and crystalline properties. Among the prepared materials, the PdO-NiO sensor calcined at 600 °C exhibited superior performance due to its hexagonal prism morphology and enhanced surface area, enabling efficient gas adsorption and desorption processes. The PdO-NiO-600 sensor demonstrated a high hydrogen response with rapid response and recovery times of 118 and 36 s, respectively, at 200 °C. The sensor exhibited excellent repeatability and stability. These results highlight the potential of PdO-NiO composites for hydrogen-sensing applications.