A room-temperature gas sensor based on 2D Ni–Co–Zn ternary oxide nanoflakes for selective and sensitive ammonia detection

Abstract

While most of the reports on NH₃ gas sensors are either based on metal oxide composites with other 2D materials, polymers or noble metals or involve multi-step-based synthesis routes, this work is the first report on a pristine ternary metal oxide, 2D NiCo₂ZnO₄ nanoflake based room-temperature (RT) NH₃ gas sensor. The 2D NiCo₂ZnO₄ nanoflakes were prepared by a one-step hydrothermal method. FESEM and TEM images displayed micro-flower like morphologies, containing vertically aligned interwoven porous 2D nanoflakes, whereas XPS and XRD data confirmed the successful growth of this ternary metal–oxide. This sensor revealed a good response, repeatability, linearity (R² = 0.9976), a low detection limit of 3.024 ppb, and a response time of 74.84 s with excellent selectivity towards NH₃ over six other VOCs. This improved performance of the sensor is ascribed to its large specific surface area (127.647 m² g⁻¹) resulting from the 2D nanoflake like structure, good electronic conductivity, variable valence states and abundant surface-active oxygen of NiCo₂ZnO₄. Thus, this highly selective 2D NiCo₂ZnO₄ based RT NH₃ gas sensor can be an attractive solution for the fabrication of next-generation NH₃ gas sensors.