Superhigh sensing response and selectivity for hydrogen gas using PdPt@ZnO core-shell nanoparticles: Unique effect of alloyed ingredient from experimental and theoretical investigations

Alloy@semiconductor core-shell nanoparticles (CSNPs) offer great advantages for hydrogen sensing due to their unique properties compared to the individual components. Herein the synthesis of alloyed PdPt@ZnO CSNPs via a hydrothermal approach is reported. PdPt@ZnO sensor exhibits an impressive sensing response of 48 with respect to Pd@ZnO (22), Pt@ZnO (14), and free ZnO (9), along with the fast response and recovery times (0.7 and 3.0 min) to 100 ppm hydrogen at 350 °C, thus outperforming current achievements of advanced single-metal hybridized semiconductors. It further delivers high selectivity and long-term stability for hydrogen sensing. These improvements are attributed to (1) high catalytic activity of alloyed PdPt core, (2) high content of oxygen vacancies and chemisorbed oxygen in ZnO shell, (3) facile two-way transfer of electrons between the core and shell, and (4) high surface area and porosity of CSNPs. In addition, DFT calculations show that alloyed PdPt core has an excellent intrinsic hydrogen adsorption capability, superior to free-standing Pd and ZnO shell. These investigations together provide mechanistic insights into the working of the system in terms of gas adsorption, reaction, and desorption.