Effect of PdO-PdO<inf>2</inf> core–shell nanocatalysts on hydrogen sensing performances of flame-made spinel Zn<inf>2</inf>SnO<inf>4</inf> nanoparticles

Abstract

In this research, flame-spray-made Pd-loaded Zn2SnO4 nanoparticles with 0.1–2 wt% Pd contents were synthesized and thoroughly investigated for hydrogen (H2) sensing. The flame-made nanoparticles were formed into sensing films via spin coating and tested towards H2 over the concentration ranging from 300 − 10000 ppm at varying working temperatures of 200–350 °C in dry air. X-ray analysis, nitrogen adsorption, and electron microscopic results revealed that Pd-loaded Zn2SnO4 nanostructures consisted mainly of 5–15 nm round and polygonal Zn2SnO4 nanoparticles uniformly decorated with 1–2 nm PdO-PdO2 core–shell nanoparticles. According to gas-sensing test data, the 1 wt% Pd-loaded Zn2SnO4 sensing film exhibited the greatest sensor response of ∼ 5612 to 10000 ppm H2 at 300 °C, which was more than three orders of magnitude higher than that of unloaded one. In addition, Pd-loaded Zn2SnO4 nanoparticles display moderately low humidity sensitivity and high H2 selectivity against C8H10, C7H8, C6H6, CH4, HCHO, CH3OH, C2H5OH, C3H6O, CH2O2, C2H4O2, C3H6O2, C4H8O2, C5H10O2 and C3H6O3. Therefore, the 1 wt% Pd-loaded Zn2SnO4 sensor is highly promising for selective and sensitive H2 detections in practical applications.