Signature of Proton-Hole Transfer in Hydrogen-Bonded Solids at 10 K

Although proton transport in water ice is well understood, proton-hole transfer (PHT) involving proton abstraction by anions remains less explored. This study investigates PHT in H2S and NH3 solids at low temperatures, aiming to determine whether these solids exhibit negative charge transport similar to that in ice. In H2S and NH3 solids at 10 K, surface HS- and NH2 - anions in hydrogen-bonded systems trigger negative current flow, providing a clear signature of PHT. This negative current is controlled by electron flow and 193 nm ultraviolet irradiation, which generates HS- and NH2 - anions on the solid surfaces. In bilayer H2S/H2O and NH3/H2O solids, a significant negative current is observed only in the NH3/H2O solid, which is attributed to the exothermic proton abstraction by NH2 - from H2O at the bilayer interface, a process not available for H2S on ice. This study is the first to demonstrate PHT-induced electrochemical behavior in hydrogen-bonded solids other than ice.