Microwave-Assisted Hydrothermal/Impregnation Synthesis of Cu₂O-Decorated rGO/In₂O₃ Nanorices for Sensitive SO₂ Gas Sensors

Abstract

In the present development, Cu 2 O-decorated reduced graphene oxide/indium oxide (rGO/In 2 O 3 ) nanorices with Cu contents of 0−1.5 wt % were synthesized by a microwaveassisted hydrothermal method combined with impregnation and studied for gas-sensing applications toward SO 2 . The material characterization results revealed that 3−5 nm Cu 2 O secondary nanoparticles were uniformly decorated on porous In 2 O 3 nanorices mixed with rGO sheets. Based on systematic gas-sensing measurements, Cu 2 O decoration on rGO/In 2 O 3 nanorices with the optimal Cu content of 1.0 wt % provided a considerably improved SO 2 response of 11.1 to 5 ppm SO 2 , which was approximately 3.3-fold as high as that of pristine rGO/In 2 O 3 nanorices (3.4) at an optimal temperature of 200 °C. Additionally, high SO 2 selectivity was attained against NO 2 , NO, CO, H 2 S, C 2 H 5 OH, C 2 H 4 , H 2 , and NH 3 . Moreover, the Cu 2 O-rGO/In 2 O 3 sensors displayed low humidity sensitivity, good repeatability, and satisfactory long-term stability. Therefore, Cu 2 O-decorated rGO/In 2 O 3 nanorices represented one of the most promising SO 2 sensors for environmental and practical applications.