Construction of heterojunctions of In2O3 nanocube with NiO for rapid detection of carbon monoxide

Abstract

Aimed at realizing the rapid and effective detection of carbon monoxide (CO) in high humidity environments, the NiO-modified In₂O₃ nanocube with different NiO loadings (1, 3, 5 mol%) was synthesized via a two-step method. Morphological characterizations revealed that the NiO modification did not alter the cubic morphology of In₂O₃, and the nanocube showed a porous structure with pore sizes of around 10 nm. The XPS analysis evidenced that the 3 mol% NiO/In₂O₃ sample owns more Ov contents (40.62%) than that of the pure In₂O₃ sample (31.73%). The gas sensing measurements demonstrated that the 3 mol% NiO/In₂O₃ sensor exhibited a decreased optimal operating temperature of 260℃ (300℃ for In₂O₃) and good stability. Compared with pristine In₂O₃, the 3 mol% NiO/In₂O₃ nanocube showed an enhanced response of 4.16 (2.73 for In₂O₃) to 500 ppm CO and a rapid response/recovery time (10 s/13 s) toward CO. Furthermore, the 3 mol% NiO/In₂O₃ sensor exhibited superior humidity resistance, enabling accurate CO detection even at 85% relative humidity. The enhanced gas sensing performance of the NiO/In₂O₃ nanocube is attributed to the unique porous cubic structure and the formation of p-n heterojunctions. This work demonstrates a viable strategy to improve the CO sensing capabilities of In₂O₃ by constructing NiO/In₂O₃ heterostructures.

Graphical abstract