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Developing a simple strategy to fabricate high-performance hydrogen sensors with long-term stability remains quite challenging. Here, we report the H 2 -sensing performance of Pd-decorated PdO hollow shells (Pd/PdO HSs). In this novel system, the catalyst nanoparticles (Pd NPs) and semiconductor support (PdO) are interconvertible, which is different from traditional hydrogen-sensing systems such as Pd/TiO 2 and Pd/ZnO. This Pd/ PdO system exhibits multiple unique properties. First, well-distributed Pd NPs with controllable density can be decorated on PdO support through a one-step NaBH 4 treatment during which PdO is partially reduced into Pd. Second, the decorated Pd NPs are physically inlaid in the PdO support, which not only prevents the agglomeration or detachment of Pd NPs but also enhances the electron transfer between Pd NPs and PdO. Third, Pd/PdO HSs can be reoxidized into PdO HSs once their sensing performance degrades, which repeatedly manipulates Pd/PdO HSs under the initial reduction process, leading to the reactivation of the sensing performance. With all these advantages, Pd/PdO HSs demonstrate a detection limit lower than 1 ppm, a response/ recovery time to 1% H 2 of 5 s/32 s at room temperature, and a repeatable reactivation ability. The strategy presented here is convenient and time saving and has no need to prefunctionalize the PdO surface for the decoration of catalyst NPs. Moreover, the unique reactivation ability of Pd/PdO system opens a new strategy toward extending the lifetime of H 2 sensors.

Precise and real-time detection of hydrogen peroxide (H2O2) is particularly necessary in pharmaceutical, industrial, and military applications because of the strong oxidability of H2O2. Here, an electrocatalytic active film with Au nanoparticles (Au NPs) embedded in a metal–organic framework (UiO-66) film was in situ prepared on the surface of an electrode for H2O2 detection. The size of Au nanoparticles and electrochemical activity of the Au nanoparticles/UiO-66 film could be controlled by manipulating the electrodeposition conditions. Since Au NPs are encapsulated into the pores of the UiO-66 film prepared in situ on a conductive substrate, aggregation of Au nanoparticles could be largely avoided, which promotes the catalytic activity and electron transfer of electrode materials. Therefore, the optimized Au nanoparticles/UiO-66 film sample presented a remarkable electrochemical response toward detection of H2O2 with an extended linear range (0.2–23 mM), a low detection limit (0.045 μM, S/N = 3), high sensitivity (329 μA mM–1 cm–2), and good stability. Furthermore, the as-prepared H2O2 sensor also displayed the advantages of excellent anti-interference performance owing to the size selectivity of the regular triangular opening channel of the UiO-66 film. Combining these advantages, the proposed sensor may open a pathway for high-performance electrochemical sensors and bioelectronics.

In situ active site titration, carbonyl group containing model catalysts, and kinetic analysis have been applied to reveal the nature of oxidized carbon nanotubes catalyzed methanol dehydration and oxidative dehydrogenation reactions.

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