A fast response ppb-level aniline gas sensor based on hierarchical hollow spheres of α-Fe2O3/α-MoO3 heterostructure

The sensing materials consist of more than one metal oxides species may endow the gas sensors with superior sensing abilities. MoO3, an acidic oxide, its precursors are usually produced in acidic solution via hydrothermal/ solvothermal method and their hierarchical structures would dissolve and collapse under alkaline circumstance, hampering the functionalization of MoO3 by other conventional metal oxides which stably exist in basic solution. In this paper, a binary metal oxide, denoted as hierarchical heterostructured alpha-Fe2O3/alpha-MoO3 hollow spheres were fabricated via a simple one-step solvothermal process. The 4.55 at% alpha-Fe2O3 -decorated alpha-MoO3 sensor exhibits remarkable sensing performance for aniline (ANI) with high sensitivity and selectivity at 217 degrees C. In particular, it shows higher response (32.5) to 30 ppm ANI compared to pristine alpha-Fe2O3 (2.1) and alpha-MoO3 (3.2) sensors, respectively, along with fast response time (3.6 s). Besides, the detection limit to ANI is further decreased from 1 ppm for the pristine alpha-MoO3 sensor to 0.01 ppm. Possible oxidation product of ANI was confirmed through GC-MS technique for the first time. The gas sensing mechanism of alpha-Fe2O3/alpha-MoO3 to ANI is speculated as the oxidation of ANI to azobenzene by chemisorbed oxygen. The possibility relating to the superior reducing gas-sensing properties of alpha-Fe2O3-decorated alpha-MoO3 to ANI was demonstrated. This work provides a logical strategy to design metal oxide composites for high performance gas sensor.

Automated summary

In this work, hierarchical heterostructured alpha-Fe2O3/alpha-MoO3 hollow spheres were successfully fabricated for gas sensing applications. The sensor exhibited high sensitivity and selectivity towards aniline at 217 degrees C, with a higher response to 30 ppm ANI compared to pristine alpha-Fe2O3 and alpha-MoO3 sensors, along with a fast response time. The detection limit to ANI was further decreased to 0.01 ppm and the gas sensing mechanism was speculated to involve the oxidation of ANI to azobenzene by chemisorbed oxygen. The study demonstrates the potential of this metal oxide composite for high-performance gas sensor applications.