A superior ethylene glycol gas sensor based on cobalt doped highly porous ZnFe₂O₄ microspheres

In this study, we synthesized porous flower-like ZnFe₂O₄ (ZF) microspheres by a straightforward hydrothermal method. To enhance the accumulation of chemically adsorbed oxygen and modify the energy surface charge distribution, we employed a doping technique. Given that the ionic radius of Co²⁺ is closely comparable to that of Zn²⁺, Co²⁺ ions were selected as an appropriate dopant for ZF. We investigated the gas sensing properties of pure ZF and doped with 5 wt% (ZFC5) and 10 wt% cobalt (ZFC10) under varying concentrations (20-500 ppm) of ethylene glycol (EG) at optimal temperature, ambient pressure and relative humidity. All three ZF-based sensing layers exhibited selective sensing capabilities towards EG, with the highest response change observed for the ZFC10 to 100 ppm EG, which was 112% greater than that of acetone. The results show that with increasing cobalt doping, the gas sensor response is significantly enhanced, for example, at 500 ppm EG, the response improved from 107.52 for ZF to 147.74 for ZFC10, with a response time of less than 3 s. The porous structure, high specific surface area, and effective doping of the ZFC-based sensor materials show significant potential for gas vapor detection, especially for EG. The results show a significant 28% increase in sensor response compared to our previous work, as well as a reduction in recovery time from 140 s to 113 s.