▎ 摘　　要

In this present work we report on room temperature operative carbon dioxide gas sensing electrodes developed by simple sonication assisted hydrothermal method. The hydrothermal treatment enhances decoration of reduced graphene oxide (rGO) layers with various ratios (9:1, 8:2, 7:3, 6:4) of nickel oxide and indium oxide nanoparticles respectively by using strong reductant hydrazine hydrate. The physiochemical, morphological and gas sensing properties of prepared pristine and composites were studied systematically and confirms the presence of materials without other impurities and high selectivity towards CO2. The fabricated sensor rGO-8:2 shows high sensitivity of 40% towards CO2 at 50 ppm. In addition, the sensor can detect up to 5 ppm concentration with quick response time of 6 s and recovery of 5 s. The optimized amount of indium addition with nickel oxide has a huge influence in CO2 sensing. This improved sensing behavior was due to the chemical combination between the rGO - metal oxides and the electronic sensitization between the surface p-n heterojunction formations. Electrode withstands long term stability of 95% for the period of 50 days when tested with 10 days interval. This simple and cost effective method will be a potential candidate for fabricating room temperature CO2 gas sensor. (C) 2020 Elsevier B.V. All rights reserved.