Exploring The Superior CH4 Gas Sensing Performance of Metal Substituted Shell (M = Ni, Zn, Co) on CuO Metal Oxide Core Derived from CuM- Based Metal Organic Framework

Abstract

Methane (CH4) with its explosive nature possesses potential threat in coal mines. Real-time methane monitoring is crucial because an explosion might occur if there is 4-5% methane in the air1. Towards this direction, substantial research has been done on chemiresistive type gas sensors based on transition metal oxides for the sensing of toxic gases because of their ease of altering the electrical conductivity upon interaction with analyte gaseous molecules2. Further, conventional metal oxide semiconductor-based gas sensors possess some limitations such as frequently include their small surface areas and high operating temperatures3. Hence, development of gas sensing materials with superior selectivity, sensitivity, reproducibility, fast response, and recovery time along with room temperature operation is necessary for practical usage. In view of this, metal organic frameworks (MOFs) have emerged as an alternative material with outstanding properties such as tunable pore structure, high crystallinity, incredibly large surface area, easy synthesis, and high gas accessibility. Hence, MOF derived core-shell heterojunction metal oxide materials can collectively reach upto the benchmark by enhancing surface area, sensitivity as well as lower response and recovery time4. This report revealed core-shell CuO/ZnO showed a comparatively higher response of S% = 12.9%, with a response and recovery time of 20 s, 25 s, respectively, towards 100 ppm of CH4 than other cation substituted shell due to higher vacancy oxygen, larger pore diameter and high specific surface area. Further, to attain efficient room temperature activity with higher sensor response and lower response, recovery time, the core-shell structure was modified with 3-D graphene oxide (3DGO). The 3DGO-CuO/ZnO gas sensor showed comparatively higher response of 20.5% towards 100 ppm of CH4 at room temperature, with the lowest response and recovery times of 8 s and 11 s, respectively