Catalytically activated quantum-size Pt/Pd bimetallic core-shell nanoparticles decorated on ZnO nanorod clusters for accelerated hydrogen gas detection

This paper presents theoretical and experimental investigations of quantum-sized (3/3 nm) Pt/Pd bimetallic core-shell nanoparticle (NP)-decorated ZnO nanorod (NR) clusters (Pt/Pd-ZnO NRs) on silicon (Si) substrate for accelerated hydrogen (H2) gas detection. Quantum-size core-shell NP synthesis, metal loading, and Pt/Pd bimetal composition were all carefully controlled by varying the deposition conditions used in the pulsed laser deposition (PLD) system. Theory suggests that the structural arrangement of bimetallic Pt shell around a Pd core can be advantageous in H2 sensing compared to the converse arrangement. Experimental analysis showed that the as-fabricated sensor exhibited a high response magnitude of 58% (10,000 ppm), a fast response time of 5 s, and a broad detection range from 0.2 to 40,000 ppm at the operating temperature of 100 °C. The fabricated sensor also exhibited a good selectivity and a negligible humidity effect over the entire detection range. The superior sensing features of the sensor can be attributed to the enhancement of hydrogen-induced changes in the work function of the Pt/Pd-ZnO NR network. More importantly, the atomic arrangements and chemical potentials of the core-shell interfacial region play vital role in accelerating the H2 sensing properties.