Theory-guided design of Pd/C nanocomposite for H2 sensing at room-temperature

Abstract

Palladium (Pd) has attracted widespread attention in the application of hydrogen gas (H2) sensors. Understanding the effect of surface structure on H2 activation is central to controlling H2 sensing performance. Here we use density functional theory (DFT) to investigate the adsorption and activation of H2 on Pd surfaces including (100), (110) and (111). The most stable adsorption configuration of H2 with the lowest dissociative adsorption energy of −0.960 eV and the charge transfer of −0.126 e from Pd to H was found on the hexagonal close-packed (hcp) site of Pd(111), suggesting that Pd(111) is most favorable for hydrogen sensing. Consistent with theoretical predication, the designed Pd nano-octahedrons enclosed by Pd(111) facets, which was synthesized by solution reduction method and characterized by multi-techniques including field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM), manifested a high sensitivity of 0.1%, a short response/recover time of 35.5/40.2 s to 4000 ppm H2 and great stability (15 cycles towards 4000 ppm H2). Accordingly, we propose that the facile dissociative adsorption of H2 on Pd(111) contributes to the readily formation of PdHx and the rapid resistance change, thus leading to the superior performance for H2 sensing.