Ultra-low Pd chemiresistive hydrogen sensor through the reverse sintering of Pd nanoparticles on the metal-organic framework ZIF-8

Optimizing metal nanoparticles (NPs) efficiency through uniform dispersion and downsizing to smaller clusters/atoms holds substantial potential to enhance catalytic activity, thereby improving the sensitivity and selectivity of the sensor. Herein, we report an ultra-high dispersion of Pd (downsized to <1 nm), achieved by synthesizing Pd/NC-ZnO via a reverse sintering route derived from Pd@ZIF-8. As a proof-of concept, uniform dispersion of Pd in Pd/NC-ZnO demonstrated a chemiresistive hydrogen (H₂) sensor with response of 4.6 ± 0.2% and response/recovery times of 6.1 ± 0.3/5.8 ± 0.3 s, respectively towards 1% H₂ at 120 °C, while Pd@ZIF-8, the precursor material remained innocent for sensing H₂. The sensor exhibited selective detection towards H₂ among typically interfering gases and was active for sensing at room temperature despite low loading of Pd (0.09 wt.%). This work highlights judicious usage of Pd by means of high dispersion and small-sized clusters/atoms stabilized by ideal supports to achieve low-cost, rapid H₂ sensors.

Graphical abstract

Despite low Pd loading (0.09 wt.%), ultra-high dispersion of Pd through reverse sintering from Pd@ZIF-8 enabled low-cost and rapid H₂ detection. The sensor Pd/NC-ZnO showed selective detection towards H₂ among typically interfering gases and was active for sensing at room temperature.