ABSTRACT Metal oxide semiconductor‐supported noble metal nanoparticles are common sensing materials for gas sensors. However, the large size and their tendency to migrate at high temperatures often lead to inferior sensing sensitivity and stability. Herein, a salt‐assistant strategy is developed to prepare fully‐exposed Ir clusters on SnO 2 nanorods, enabling highly sensitive and stable H 2 sensing. By introducing potassium nitrate as a precursor, it was found that the nitrate can induce the Ir species to be exposed on the SnO 2 surface in the form of highly‐distributed nanoclusters with an average size of less than 1 nm. Meanwhile, the strong interaction between SnO 2 and Ir clusters ensures the durability of the catalysts under elevated temperatures (300°C). The final Clu‐Ir/SnO 2 sensors exhibit excellent H 2 sensing performance, featuring a high response value (46 @ 4000 ppm H 2 ), fast response/recovery time (4.6/3.7 s @ 4000 ppm H 2 ), and a low detection limit (as low as 1 ppm). Notably, no significant change in the dispersion state of the Ir metal is observed even after 60 days of continuous use, demonstrating excellent long‐term stability. In situ Raman, ex situ X‐ray photoelectron spectroscopy (XPS), and H 2 ‐temperature‐programmed reduction (TPR) results prove that the sensitization mechanism of fully dispersed and exposed Ir clusters involves oxygen capture and activation, H 2 adsorption and conversion to H species, and optimization of electron transfer pathways to SnO 2 . Overall, this study provides valuable insights into the synthesis of fully exposed cluster catalysts capable of stable operation under high temperatures in gas sensing applications.
Jiang et al. (Sun,) studied this question.