title: Pristine Ta3N5Nanotubes: Trap-Driven High External Biasing Perspective in Semiconductor/Electrolyte Interfaces.
abstract: Ta3N5is a promising photoelectrode for solar hydrogen production; however, to date pristine Ta3N5electrodes without loading co-catalysts have presented limited photoelectrochemical (PEC) performance. In particular, large external biasing has been required to run water oxidation, the origin of which is investigated herein. Ta3N5nanotubes (NTs) prepared by nitridation were characterized by a wide range of techniques. The bandgap was confirmed by a novel PEC technique. Nondestructive synchrotron-excited XPS has shown the presence of reduced Ta species deeper in the Ta3N5surface. Lower photocurrent and transient spikes that were intense at lower applied biasing were observed under water oxidation; however, spikes were inhibited in the presence of a sacrificial agent and photocurrent was improved even at low biasing. It was observed for the first time that the lower PEC performance under water oxidation can be attributed to the presence of interband trapping states associated with pristine Ta3N5NTs/electrolyte junction. These states correspond to the structural defects in Ta3N5, devastate PEC performance, and present the necessity to apply higher biasing. The key to circumvent them is to use a sacrificial agent in the electrolyte or to load a suitable co-catalyst to avoid hole accumulation under water oxidation, thereby improving the phootocurrent. The findings on the interband states could also provide guidance for the investigation of PEC properties of new types of semiconducting devices.
authors.affiliation: Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 PO Box - 15051, 91501-970, Porto Alegre, RS, Brazil.|Programa de Pós-Graduação em Engenharia de Minas, Metalúrgica e de Materiais - PPGE3M, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Sherdil
authors.initials: S
authors.lastname: Khan
authors.affiliation: Instituto de Quimica, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 PO Box - 15003, 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Marcos J L
authors.initials: MJ
authors.lastname: Santos
authors.affiliation: Programa de Pós-Graduação em Engenharia de Minas, Metalúrgica e de Materiais - PPGE3M, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Célia F
authors.initials: CF
authors.lastname: Malfatti
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Jairton
authors.initials: J
authors.lastname: Dupont
authors.affiliation: Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 PO Box - 15051, 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Sérgio R
authors.initials: SR
authors.lastname: Teixeira
keywords: applied biasing; nanotechnology; photoelectrochemistry; thermal nitridation; trapping states