High-Temperature Hydrogen Gas Sensor Based on Three-Dimensional Hierarchical-Nanostructured Nickel–Cobalt Oxide

The design of hierarchical metal oxide nanostructured systems has emerged as an effective strategy for improving the performance of hydrogen (H2) gas sensing to facilitate a H2 economy. H2 gas sensors that can operate at elevated temperatures (≥500 °C) are necessary for advanced combustion monitoring and emission control in the automotive industry. Here we report on a hierarchical three-dimensional nickel and cobalt oxide nanomaterial as an efficient high-temperature gas sensor for H2 detection. Our study reveals that the response of the nickel–cobalt oxides strongly depends on the morphology and ratio of Ni/Co. The flower-like NiO nanomaterial demonstrates a p-type response to H2 at 300–500 °C and an n-type response to H2 gas at 600 °C. The developed nickel–cobalt oxide sensor exhibits a unique performance and superior sensitivity at elevated temperatures of ∼500 °C but a negligible response at 300–400 °C. A high surface area with small nanopores and a sensitive change in the crystalline nature at >500 °C make this new nickel–cobalt oxide nanomaterial distinctive for the detection of H2 at such high temperatures. The novel H2 gas sensor developed in this study exhibits excellent sensitivity, selectivity against various gaseous mixtures, and high stability, demonstrating its promising practical functionality.