Plasmonic Hydrogen Evolution at p-Type Semiconductor Electorode

Abstract

The efficient control of the visible light driven hydrogen evolution reaction can be recognized as the one of the promising challenge for the sustainable society. It can be said that the wide-band semiconductor electrode is the promising material for the photo-energy conversion system. However, various semiconductor electrodes have the limitation to the ultraviolet region because of their wide band gap energy. Recently, plasmoic photoelectric conversion system, which is the combination of the plasmon active metal nano-structures with the semiconductor substrate, has been received much attention because the system shows the visible light response characters beyond the limitation of the limitation. In this system, the electrons excited in the metal structures injected into the conduction band of the n-type semiconductor and the remained holes are consumed through the oxidation reaction. Up to now, various plasmon-induced chemical reactions, even the water splitting, have been proposed. As our previous study, we have not only visualized the reaction active sites but also determined the reaction active species through the polymerization reactions of the conductive polymer. Although well-established systems have been reported, the direct control of the reduction reaction at the metal-semiconductor interface by the excited electrons has not been well examined. This is because the almost plasmonic photoconversion systems consist of the n-type semiconductor electrode and applied the generated holes to the reactions. In this study, we have tried to establish the plasmon-induced hydrogen evolution system by the introduction of the plasmon-active metal nano-structures into the p-type semiconductor substrate. By supporting the plasmonic structures, we have confirmed the photo-current generation under the visible light illumination.[1] Through the photocurrent measurements and the incident photon to current conversion efficiency obtained under different pH conditions, we have confirmed the unique pH dependence. In addition to these, we have also investigated the isotopic effect on the hydrogen evolution reaction to clarify the unique surface molecular process. Through the various photoelectrochemical measurements, we are sure that our plasmonic hydrogen evolution system could be one of the good candidate for future light energy conversion system. [1] D. Sato, H. Minamimoto, and K. Murakoshi, Chem. Lett., in press.