Alkalization treatment engineering gas sensing selectivity improvement of ZnCo2O4 microspheres toward xylene

Improving the recognition ability of gas sensing materials toward target gases is one of the eternal themes of gas sensor research. Here, a feasible alkalization treatment strategy is proposed and is used to greatly improve gas sensing selectivity and response of oxide semiconductor based sensing materials. To be specific, ZnCo2O4 microspheres could be prepared through a solvothermal strategy with annealing, but do not exhibit gas sensing selectivity. When treated with 0.5 M sodium hydroxide aqueous solution, the alkalized ZnCo2O4 microspheres (ZCO-0.5) show significantly enhanced xylene gas sensing selectivity at 160 °C. Meanwhile, the ZCO-0.5 sensor also exhibits superior stability, repeatability and reliability toward xylene gas. The enhanced selectivity of xylene gas sensing originates from more exposed metal-oxygen bonds, OH functional groups, -O terminal groups and Co3+ ions on the surfaces of ZnCo2O4 microspheres introduced by the alkalization treatment of sodium hydroxide solution with appropriate concentration. The alkalization treatment method in this study could be applied to other oxide semiconductors to enhance their gas sensing selectivity and performances.