Ambient Sensitive Charge Transfer from GaN to Pt during a Photocatalytic Reaction.

An n-type GaN epitaxial thin film surface modified with a cocatalyst, Pt comb, showed photocatalytic evolution of hydrogen from water under irradiation. Direct measurement of electrochemical potentials of the n-type GaN layer and Pt comb revealed that the potentials of Pt comb were well matched with that of an n-type GaN layer, indicating that the n-type GaN-Pt interface behaved as an Ohmic contact during the reaction. However, the interface behaves as a Schottky contact in air. Newly developed in situ current-voltage ( I-V ) measurements revealed that the Ohmic contact was realized only with hydrogen in both air and an aqueous solution. This ambient sensitive charge transfer will likely play an important role in photocatalysis.