Effect of hydrogen Evolution Reaction on conductance quantization of Au, Ag, Cu nano contacts

We have mechanically fabricated Au, Ag, and Cu nano contacts in solution under the electrochemical potential control. At the hydrogen evolution potential, fractional conductance peaks appeared near 0.5 G0 (G0=2e/h) in the conductance histogram of Au and Cu. This fractional conductance peak was not observed in the conductance histogram of Ag. In the case of Au nano contacts in 50 mM H2SO4 solution, a 0.1 G0 peak appeared in the conductance histogram, as well as the 0.5 G0 peak. The origin of the fractional conductance peak and its metal dependence were discussed based on previously reported values of metal-hydrogen binding energy, which was estimated by the exchange current density for the hydrogen evolution reaction.