title: Photoelectrochemical activity on Ga-polar and N-polar GaN surfaces for energy conversion.
abstract: Hydrogen generation through direct photoelectrolysis of water was studied using photoelectrochemical cells made of different facets of free-standing polar GaN system. To build the fundamental understanding at the differences of surface photochemistry afforded by the GaN {0001}and {000-1}polar surfaces, we correlated the relationship between the surface structure and photoelectrochemical performance on the different polar facets. The photoelectrochemical measurements clearly revealed that the Ga-polar surface had a more negative onset potential relative to the N-polar surface due to the much negative flat-band potential. At more positive applied voltages, however, the N-polar surface yielded much higher photocurrent with conversion efficiency of 0.61% compared to that of 0.55% by using the Ga-polar surface. The reason could be attributed to the variation in the band structure of the different polar facets via Mott-Schottky analyses. Based on this work, understanding the facet effect on photoelectrochemical activity can provide a blueprint for the design of materials in solar hydrogen applications.
authors.forename: Yan-Gu
authors.initials: YG
authors.lastname: Lin
authors.forename: Yu-Kuei
authors.initials: YK
authors.lastname: Hsu
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Basilio
authors.forename: Yit-Tsong
authors.initials: YT
authors.lastname: Chen
authors.forename: Kuei-Hsien
authors.initials: KH
authors.lastname: Chen
authors.forename: Li-Chyong
authors.initials: LC
authors.lastname: Chen