Construction of heterojunctions of InO nanocube with NiO for rapid detection of carbon monoxide.

Aimed at realizing the rapid and effective detection of carbon monoxide (CO) in high humidity environments, the NiO-modified InO 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 InO, and the nanocube showed a porous structure with pore sizes of around 10 nm. The XPS analysis evidenced that the 3 mol% NiO/InO sample owns more Ov contents (40.62%) than that of the pure InO sample (31.73%). The gas sensing measurements demonstrated that the 3 mol% NiO/InO sensor exhibited a decreased optimal operating temperature of 260℃ (300℃ for InO) and good stability. Compared with pristine InO, the 3 mol% NiO/InO nanocube showed an enhanced response of 4.16 (2.73 for InO) to 500 ppm CO and a rapid response/recovery time (10 s/13 s) toward CO. Furthermore, the 3 mol% NiO/InO sensor exhibited superior humidity resistance, enabling accurate CO detection even at 85% relative humidity. The enhanced gas sensing performance of the NiO/InO 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 InO by constructing NiO/InO heterostructures.