Ta3N5 Nanotube Arrays for Visible Light Water Photoelectrolysis

• Published in: Nano letters 2010-03, Vol.10 (3), p.948-952
• Main Authors: Feng, Xinjian, LaTempa, Thomas J, Basham, James I, Mor, Gopal K, Varghese, Oomman K, Grimes, Craig A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrolysis - instrumentation; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Equipment Design; Equipment Failure Analysis; Exact sciences and technology; Light; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Nitrogen - chemistry; Nitrogen - radiation effects; Photochemistry - instrumentation; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tantalum - chemistry; Tantalum - radiation effects; Transducers; Water - chemistry
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl903886e

Tantalum nitride (Ta3N5) has a band gap of approximately 2.07 eV, suitable for collecting more than 45% of the incident solar spectrum energy. We describe a simple method for scale fabrication of highly oriented Ta3N5 nanotube array films, by anodization of tantalum foil to achieve vertically oriented tantalum oxide nanotube arrays followed by a 700 °C ammonia anneal for sample crystallization and nitridation. The thin walled amorphous nanotube array structure enables transformation from tantalum oxide to Ta3N5 to occur at relatively low temperatures, while high-temperature annealing related structural aggregation that commonly occurs in particle films is avoided. In 1 M KOH solution, under AM 1.5 illumination with 0.5 V dc bias typical sample (nanotube length ≈ 240 nm, wall thickness ≈ 7 nm) visible light incident photon conversion efficiencies (IPCE) as high as 5.3% were obtained. The enhanced visible light activity in combination with the ordered one-dimensional nanoarchitecture makes Ta3N5 nanotube arrays films a promising candidate for visible light water photoelectrolysis.