Room Temperature Ethanol Sensing Properties of Nanostructured Ni(OH) ₂ ‐Graphene Composite

This study presents a simple hydrothermal method for synthesizing a composite of β‐nickel hydroxide on reduced graphene oxide (rGO) for potential use as an ethanol sensor. X‐ray diffraction analysis confirmed the formation of β‐phase of crystalline Ni(OH) ₂ whereas electron microscopy revealed the existence of uniformly distributed β‐Ni(OH) ₂ particles (35–40 nm long hexagonal prism‐like) on rGO sheets. Surface adsorption studies confirmed unique surface properties of the composite material with a specific surface area of 207 m ² /g and pore diameter of 13.4 nm. When the hybrid composite was used as a film on a glass substrate, it demonstrated exceptional ethanol‐sensing capabilities at room temperature. Against exposure to 75 ppm of ethanol vapor, the β‐Ni(OH) ₂ /rGO film exhibited a response of ∼250 along with excellent repeatability over multiple cycles. Further, the sensor showed a very fast response time of 2 s along with a modest recovery time of 27 s. The hybrid film also displayed high selectivity to ethanol vapor, as evident from the negligible responses to other alcoholic and nonalcoholic vapors as well as humid air (50% relative humidity, RH). Further, the change in infrared absorption intensity was measured to investigate the decomposition of ethanol vapor on the sensor surface, revealing that CO ₂ evolution was higher for β‐Ni(OH) ₂ /rGO compared to that for β‐Ni(OH) ₂ indicating a strong influence of rGO on sensor performan. Overall, the synthesized β‐Ni(OH) ₂ /rGO shows good promise as a low‐cost material for room temperature ethanol sensing.