Hollow Spherical ZnO with Mesoporous Shell for Highly Enhanced Gas Sensitivity and Selectivity.

In this work, ZnO hollow spheres (ZnO-HS) with mesoporous shells were successfully synthesized via a facile two-step method. The hollow structure provides sufficient space and active sites for adsorbing gases. The mesoporous shells assembled from nanoparticles facilitate the diffusion of gas molecules into the inner space and ensure full contact with ZnO. Consequently, ZnO-HS-600 gas sensors deliver a satisfactory response to volatile organic compounds (VOCs) and an excellent response-recovery time at the optimal working temperature of 300 °C, i. e., acetone (9 and 5 s), ethanol (10 and 6 s), and methanol (12 and 14 s), respectively. By combining the theoretical calculation and the experimental observation, the relationship between the structure and performance has been established. The results demonstrate that ZnO-HS-600 materials meet the regional depletion condition, i. e., L ≥ 2Ls , further explaining its superior response-recovery time. Our work provides a prospective strategy for high-performance ZnO gas sensors via structural design and theoretical calculations.