  In order to realize applications of hydrogen-adsorbed graphene, a main issue
is how to control hydrogen adsorption/desorption at room temperature. In this
study, we demonstrate the possibility to tune hydrogen adsorption on graphene
by applying a gate voltage. The influence of the gate voltage on graphene and
its hydrogen adsorption properties was investigated by electrical transport
measurements, scanning tunneling microscopy, and density functional theory
calculations. We show that more hydrogen adsorbs on graphene with negative gate
voltage (p-type doping), compared to that without gate voltage or positive gate
voltage (n-type doping). Theoretical calculations explain the gate voltage
dependence of hydrogen adsorption as modifications of the adsorption energy and
diffusion barrier of hydrogen on graphene by charge doping.
