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

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.