Sensitive, Selective, and Fast Detection of ppb-Level H₂S Gas Boosted by ZnO-CuO Mesocrystal

ZnO-CuO mesocrystal was prepared via topotactic transformation using one-step direct annealing of aqueous precursor solution and assembled into a H₂S sensor. The ZnO-CuO mesocrystal-based sensor possesses good linearity and high sensitivity in the low-concentration range (10-200 ppb). Compared to pure CuO, the as-prepared ZnO-CuO mesocrystal sensor exhibited superior H₂S sensing performance with a response ranging from 8.6 to 152 % towards H₂S concentrations from 10 ppb to 10 ppm when applied at the optimized working temperature of 125 °C. The sensor showed excellent repeatability and good selectivity towards H₂S gas even at a concentration four orders of magnitude lower than the interfering gases, such as H₂, CO₂, CO, NO₂, acetone, and NH₃. The improved sensitivity could be attributed partially to the effective diffusion of analyte gas through the mesocrystal surface and the abundant accessible active sites. Moreover, the nanoscale p-n junctions within the mesocrystal, which could effectively manipulate the local charge carrier concentration, are also beneficial to boost the sensing performance.