Porous CoTiO3 with highly surface defects as effective sensing materials for ethanol detection

Abstract

A series of nano/micro-structured CoTiO3 powders were synthesized using a facile mixed-solvothermal method, by adjusting the volume ratio of ethylene glycol (EG) to anhydrous ethanol in the mixed solvent. Nitrogen adsorption–desorption and electron microscopic analyses revealed that the as-prepared CoTiO3 products possess a bimodal porous structure with interconnected pore channels, which have great advantages for the diffusion of target gas and the effective utilization of active sites. The porous CoTiO3 obtained at the volume ratio of EG to anhydrous ethanol of 1:2 in the mixed solvent demonstrated the highest sensitivity (20.3) and rapid response time (7 s) to low concentration ethanol (20 ppm) at working temperature 300 °C. Moreover, excellent reproducibility and stability can be achieved within six cycles. Photoluminescence (PL) results illustrated that the porous CoTiO3 with the best sensing performance has more abundant surface defects than other samples. These defects can act as reactive sites to facilitate more O2 adsorption, leading to the enhanced accumulation of positive holes on the surface and an increase in the gas sensitivity. In view of the excellent sensing characteristics to low concentration ethanol and the facile preparation method, the obtained porous CoTiO3 products are promising candidates for fabricating effective ethanol sensors.