We have demonstrated plasmonic photocurrent generation using gold nanostructured TiO2 photoelectrode. In this system, H2O are used as electron sources through the confirmation of stoichiometric evolution of O2. Based on the mechanism, we have successfully developed a plasmon-induced water splitting system using Au nanoparticles-loaded SrTiO3 photoanode. The quantity of H2 evolved from the surface of Pt cathode, which was used as a reduction co-catalyst, was twice of O2 stoichiometrically evolved from the Au/SrTiO3 photoanode. The action spectrum of H2 evolution corresponded to the localized surface plasmon resonance (LSPR) band, indicating that the plasmon-induced charge separation at the Au/SrTiO3 interface promotes water oxidation and the subsequent reduction of protons on the Pt cathode surface.
To enhance the probability of interactions between light and the photoanode, we have constructed a plasmonic absorber constituted from AuNP/TiO2/Au-film. A strong light absorption was demonstrated due to the coupling between LSPR and the cavity mode in the TiO2 thin film. The absorption calculated by 1-T-R showed a more than 90% from 550 to 650 nm wavelength. We have successfully demonstrated that the water splitting efficiency was promoted by the strong absorption.
We have also constructed an artificial-photosynthesis system that produces NH3 by a photofixation of a N2 molecule based on visible light irradiation. Ruthenium was used as a co-catalyst for the NH3 synthesis. The action spectrum of apparent quantum efficiency of NH3 evolution showed good agreement with the LSPR band. In addition, we revealed that NH3 could be obtained with ~100% selectivity by using zirconium/zirconium oxide co-catalyst. These findings blaze new methods for energy-efficient photocatalytic production of NH3 using solar light, water, and N2 gas.
报告人简介：Prof. Hiroaki Misawa （三澤 弘明) 日本北海道大学电子科学研究所教授、台湾国立交通大学应用化学系讲座教授。1984年获筑波大学博士学位, 此后在美国University of Texas at Dallas从事博士后研究。自1986年先后任筑波大学助理教授、德岛大学副教授(1993)、教授(1995)、北海道大学教授(2003)、北海道大学电子科学研究所所长(2009-2013)。他领导和主持了日本文部科学省(MEXT)、JST、JSPS的多项重大科研项目(Grant-in-Aid for Scientific Research on Priority Areas、ERATO、CREST等)、任职多个重要学术组织、科研项目、学术期刊(ACS Photonics等)的顾问，2013-2014年任日本光化学协会会长。他先后在Nature、Chem. Rev.、JACS、Angew. Chem.、PRL、Adv. Mater.、ACS Nano、Light: Sci. Appl.、Nat. Commun.、NPG Asia Mater.等重要学术期刊发表论文300余篇，近年获日本文部科学大臣(科学技术)奖(2015)、日本化学学会学会赏(2016)。目前主要研究兴趣集中在纳米材料化学、光化学、微纳光科学与技术、激光加工等，特别是基于表面等离激元的光电转换和人工光合成的研究。
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