Pd promoted oxygen species activation of ZnO nanosheets for enhanced hydrogen sensing performance and its DFT investigation

The sensing performance of ZnO-based metal oxide semiconductors to H2 can be significantly enhanced after decoration of noble metals, and it is of great significant to understand the mechanism and structure-activity relationship between materials and sensing performance, which facilitate the designation of high-performance sensing materials. Herein, we have synthesized Pd-decorated two-dimensional (2D) ZnO nanosheets. A contrastive study based on H2 gas sensing performance of pristine ZnO and Pd-loaded ZnO (PZO) are carried out. According to the results, PZO exhibit superior sensing performance towards H2 (Ra/Rg=17.6, 160 °C), which is much higher than the pristine ZnO nanosheets. Moreover, the PZO also exhibit robust sensing stability and selectivity, detailed structural investigations illustrate that the electronic and surface properties of Pd-ZnO interface play the vital role in H2 sensing process. Density functional theory (DFT) calculation illustrates that H atoms trend to be dissociated at the surface Pd0 sites and the more surface oxygen vacancies are extremely desirable for H2 sensing. The superior H2 sensing of PZO is mainly attributed to the synergistic mechanism of Pd catalytic site and oxygen vacancy (OV). Our works pave the way for designation of high performance H2 sensing materials for the safety of development and utilization of H2.