Enhancement in solar hydrogen generation efficiency using a GaN-based nanorod structure

A significant enhancement in solar hydrogen generation has been achieved using a GaN-based nanorod array structure as a photoelectrode in comparison with a planar one fabricated from the same parent wafer. The nanorod array structure was formed by dry etching using a self-organised nickel nanomask. Under identical illumination conditions in hydrochloric acid solution, the photoelectrode with the nanorod array structure has demonstrated a photocurrent enhancement with a factor of 6 and an enhancement in the rate of hydrogen generation with a factor of 7. The enhancement in solar hydrogen generation is attributed to a massive improvement in light absorption area, reduced travelling distance for the migration of the photogenerated carriers to the semiconductor/electrolyte interface, and surface band bending.