Continuously improved gas-sensing performance of SnO2/Zn2SnO4 porous cubes by structure evolution and further NiO decoration

Improving the gas-sensing performance of semiconducting metal oxide nanocomposites by optimizing their structure and composition has attracted an increasing interest. In this paper, a reliable sacrificial template method was developed to fabricate a series of SnO2/Zn2SnO4 (TZTO) nanostructures, including TZTO porous cubes (TZTO-PCs), TZTO porous hollow cubes (TZTO-PHCs), and NiO-decorated TZTO porous hollow cubes (NTZTO-PHCs). ZnSn(OH)6 solid cubes (ZHS-SCs) with the edge-length about 500 nm were first synthesized by a facile sonochemistry method, and then chemically etched in NaOH aqueous solution to prepare ZHS hollow cubes (HCs). By using the as-prepared ZHS-SCs and ZHS-HCs as sacrificial templates, TZTO-PCs, TZTO-PHCs, and NTZTO-PHCs with different NiO contents were easily synthesized, respectively. It was found that through the structure evolution from PC to PHC, the sensitivity of TZTO to ethanol was remarkably improved. Significantly, superior ethanol-sensing properties, such as lower optimal operating temperature, higher sensitivity, and a wider range of response linearity were further achieved by decorating TZTO-PHCs with NiO. The optimal content of NiO in NTZTO-PHCs was determined to be 0.75 mol%. The improved sensing mechanism based on structure and composition evolution for the present NTZTO-PHCs was discussed in detail.