TiO2/ZnCo2O4 porous nanorods: Synthesis and temperature-dependent dual selectivity for sensing HCHO and TEA

Abstract Selective detection of different gases on a sensor based on metal oxide semiconductor (MOS) is greatly desired but still remains a challenge. Herein, we demonstrated a strategy to realize highly sensitive and selective detection of formaldehyde (HCHO) and triethylamine (TEA) by using TiO2-decorated ZnCo2O4 porous nanorods (PNRs) as sensing material. The TiO2/ZnCo2O4 PNRs were prepared via a facile dual-oxalate sacrificial template method, in which ZnC2O4/CoC2O4 solid nanorods were synthesized in advance through a simple room temperature co-precipitation method and then applied as sacrificial templates for TiO2/ZnCo2O4 PNRs by immersing them in C10H14O5Ti ethanol solution before calcination. The prepared TiO2/ZnCo2O4 PNRs feature an assembly of randomly stacked nanoparticles with the size about 20 nm. In comparison with pure ZnCo2O4 PNRs, the TiO2/ZnCo2O4 PNRs showed an improved gas sensitivity. More importantly, the sensor based on 4TZCO (TiO2/ZnCo2O4 PNRs with optimized TiO2 content of 4 wt%) could realize selective detection of HCHO and TEA at ppm level by controlling the working temperature at 130 °C and 220 °C, respectively. The ZnCo2O4-TiO2 p-n heterostructure-related gas sensing mechanism was discussed.