Amorphous Pd-assisted H₂ detection of ZnO nanorod gas sensor with enhanced sensitivity and stability

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>For monitoring H<SUB>2</SUB> concentrations in air, diverse resistive gas sensors have been demonstrated. In particular, Pd-decorated metal oxides have shown remarkable selectivity and sensing response for H<SUB>2</SUB> detection. In this work, H<SUB>2</SUB> sensing behavior of amorphous Pd layer covering ZnO nanorods (am-Pd/ZnO NRs) is investigated. This is the first report on the enhanced gas sensing performance attained by using an amorphous metal layer. The amorphous Pd layer is generated by reduction reaction with a strong reducing agent (NaBH<SUB>4</SUB>), and it covers the ZnO nanorods completely with a thickness of 2–5 nm. For comparison, crystalline Pd nanoparticles-decorated ZnO nanorods (c-Pd/ZnO NRs) are produced using a milder reducing agent like hydrazine. Comparing the c-Pd/ZnO NRs sensor and other previously reported hydrogen sensors based on the crystalline Pd and metal oxides, the am-Pd/ZnO NRs sensor exhibits a remarkable sensing response (12,400% at 2% H<SUB>2</SUB>). The enhancement is attributed to complete cover of the amorphous Pd layer on the ZnO NRs, inducing larger interfaces between the Pd and ZnO. In addition, the amorphous Pd layer prevents surface contamination of the ZnO NRs. Therefore, the am-Pd/ZnO NRs sensor maintains initial sensing performance even after 5 months.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facile synthesis of ultrathin amorphous Pd layer (2–5 nm) on ZnO nanorods. </LI> <LI> Comparison of sensing behavior between amorphous and crystalline Pd-coated ZnO nanorods sensors. </LI> <LI> Demonstration of superior sensing response (12,400%) of amorphous Pd-coated ZnO nanorods sensors. </LI> <LI> High stability of amorphous Pd-coated ZnO nanorods sensors. </LI> </UL> </P>