Template-free synthesis of Ta3N5 nanorod arrays for efficient photoelectrochemical water splitting

Abstract

We report the template-free synthesis of Ta3N5 nanorod array films grown on Ta foil by a combination of a vapor-phase hydrothermal process and subsequent nitriding. The Ta3N5 nanorod array film modified with Co(OH)x when used as a photoanode in a photoelectrochemical cell for water splitting yields a stable photocurrent density of 2.8 mA cm(-2) at 1.23 VRHE under AM 1.5G simulated sunlight. The incident photon-to-current conversion efficiency at 480 nm is determined to be 37.8%.

Effects of intrinsic defects and extrinsic doping on the electronic and photocatalytic properties of Ta3N5

“…[1][2][3] However, most of the photocatalytic materials possessing the ability to split water allow only UV optical absorption, which greatly restricts their energy conversion efficiency. Therefore, transition metal (oxy)nitrides such as LaTaO 2 N 8-10 and Ta 3 N 5 [11][12][13][14] , have attracted massive research interest during the past decades because of the suitable band gap and band edge positions. [4][5][6][7] It is unanimously accepted that an ideal semiconductor material for the photoelectrode should have a suitable band gap of about 2.0 eV to meet both the dynamic reaction barrier and a wide range of optical absorption.…”

Strongly Enhanced Water Splitting Performance of Ta3N5 Nanotube Photoanodes with Subnitrides

“…[ 10,[12][13][14][15][16] These factors are benefi cial for the incident light absorption and enhanced PEC water splitting effi ciency of Ta 3 N 5 photoelectrodes. The overall composition of the nitride layer was estimated as Ta 3− x N 5− y O y (i.e., implying the presence of subnitrides).…”

“…[ 15b,c ] The thickness of aligned NT layers could be controlled from 300 nm to several micrometers (>10 µm) with a tube wall (10-50 nm) compared to 300-700 nm layer thickness of NR structures. [10][11][12][13][14][15][16] These 1D nanostructures possess advantages for PEC water splitting, such as an enlarged surface area, small radial size (i.e., facilitating the transportation of minority charge carriers to the solid-liquid interface without recombination), and a high aspect ratio (i.e., a long axial length enabling a maximum absorption of incident light). Particularly, for the water oxidation reaction of the bare Ta 3 N 5 NT photoelectrodes, the photocurrent can reach up to 4.0-5.3 mA cm −2 at 1.6 V RHE in 1 M NaOH under AM 1.5G illumination, [ 16 ] while only ≈2.0 mA cm −2 is obtained for the NRs under the same conditions.…”

Solar fuel production: Strategies and new opportunities with nanostructures

“…In order to drive the redox reactions in the photoelectrode system, the photogenerated minority and majority carriers are required, respectively, to reach the photoelectrode/electrolyte interface and the counter electrode. Shorter carrier collection pathways imply reduced transfer times for charge carriers through the semiconductor bulk; therefore, shortened carrier collection pathways through nanostructuring of semiconductors are potentially beneficial to reduce the recombination probability of electron-hole pairs [29]. (2) Enlarged specific surface area.…”