Intricate nature of Pd nanocrystal–hydrogen interaction investigated using thermolysed Pd hexadecylthiolate films

Abstract

Nanocrystalline Pd films are derived by thermolysing Pd hexadecylthiolate at different temperatures (195–250 °C) to obtain films with different resistances, 3–115 Ω. The films essentially consist of Pd nanocrystals (5–40 nm) amidst amorphous carbon as evidenced by electron microscopy and Raman measurements. The response to H₂ is seen as a jump in the resistance which varied proportionally with the base resistance, the slope being ∼0.2. Interestingly, the change over from H₂ to purging N₂ (or Ar) atmosphere is accompanied by a kink-like feature in the electrical response, which is linked to depletion of hydrogen from the nanocrystal surface and its backfilling from the core. The presence of O₂ in the purging atmosphere affects adversely the formation of the kink.