Hierarchically porous ZnO with high sensitivity and selectivity to H2S derived from biotemplates

Hierarchical porous wood-templated ZnO has been successfully synthesized using Lauan and Fir woods as template through a simple hydrothermal bioinspired approach. The template type and calcination temperature in the preparation process have a large effect on the morphologies and porous structures of ZnO according to FESEM, TEM, mercury porosimetry and N2 adsorption investigations. The gas sensing performances of wood-templated and non-templated ZnO were investigated using H2, CO, H2S, NH3, Formaldehyde, Methanol, Ethanol, Acetone, and Isobutene. The article studies the effects of wood template, calcination temperature, and working temperature of gas flow on the gas sensitivity and selectivity in detail. It is revealed that wood-templated ZnO has excellent sensitivity and selectivity to H2S due to inheritance of wood's hierarchical porous structure. The sensing response to H2S of Fir-templated ZnO is about 5.1 times higher than that of non-templated ZnO. Fir-templated ZnO calcined at 600 °C, has the best sensing properties including the highest gas sensing response, the highest selectivity coefficients of H2S and the shortest response and recovery time. The selective sensing mechanism has been discussed from some key aspects, such as gas properties, gas–solid reactions, grain size and hierarchical porous microstructures.