Simple preparation of yolk-shell ZnCr2O4 microspheres and their application to xylene gas sensor

Spinel-type oxides have attracted more and more attention due to their high thermodynamic stability, good catalytic characteristic and flexibly tunable features. Herein, we report the synthesis of yolk-shell ZnCr2O4 microspheres with superior xylene sensing properties by a one-step solvothermal approach. The gas sensing properties of the as-prepared ZnCr2O4 microspheres were investigated. The sensor based on yolk-shell ZnCr2O4 microspheres showed excellent selectivity to xylene having a high response value of 200.7–100 ppm xylene, which was almost 77 times than that of Cr2O3 microspheres at 225 °C. As for the detection limit, the response value of sensor to 0.5 ppm xylene was 1.2. In addition, after 22 days of measurement, it could still keep the response of nearly 200–100 ppm xylene, indicating good long-term stability. The excellent gas sensing performances of sensor to xylene can be ascribed to the yolk-shell architecture with a large specific surface area and the high surface adsorbed oxygen species concentration.