Tantalum nitride nanotube photoanodes: Establishing a beneficial back-contact by lift-off and transfer to titanium nitride layer

Abstract

In this work we introduce the use of TiN/Ti2 N layers as a back contact for lifted-off membranes of anodic Ta3N5 nanotube layers. In photoelectrochemical H2 generation experiments under simulated AM 1.5G light, shift of the onset potential for anodic photocurrents to lower potentials is observed, as well as a higher magnitude of the photocurrents compared to conventional Ta3N5 nanotubes (~0.5 V RHE ). We ascribe this beneficial effect to the improved conductive properties of the TiNx -based back contact layer that enables a facilitated electron-transport for tantalum-nitride based materials to the conductive substrate.Key words: tantalum nitride; nanotube membranes; titanium nitride; water splitting Link to the published article: http://dx

Ta3N5/Co(OH)x composites as photocatalysts for photoelectrochemical water splitting

“…1. The synthesis of Ta3N5 NTs starts from the growth of vertically aligned Ta2O5 NTs on a piece of Ta foil through a two-step anodization, with optimized parameters based on previously reported methods 17,21,30,33 . The Ta foil was cut and cleaned by sonication in a sequence of acetone, isopropanol and DI H2O and dried under a N2 flow.…”

“…NHE, much less than the best performance in the literature, it should be mentioned that in order to have a more reliable photocurrent the best results obtained from first LSV was not used here. In addition, the stability of nanotube-based Ta3N5 photoanodes for PEC water splitting is rarely mentioned in the literature 17,18,21,30,31,42 , even though most of them claim photocurrent improvements at a certain applied potential. However, stable PEC water splitting performance by co-catalyst modified Ta3N5 synthesized in other morphologies have already been reported in the literature, such as Co-Pi modified Ta3N5 nanorods 23 , Co-Pi+Co(OH)x/NiFe-LDH multiple co-catalysts modified Ta3N5 nanorods 22 and ferrihydrite (Fh) protected Ta3N5 film 46 .…”

“…Recently 1D Ta3N5 materials, such as nanotubes 21 and nanorods 22 , have attracted attention due to their unique properties in charge transport and significantly increased surface area, which is usually in combination with the co-catalysts coating to further boost the solar light conversion efficiency 22-24 . This work focuses on 1D Ta3N5 nanotubes (NTs) as the main photoelectrode material due to the relative easiness to synthesize it and scale up. The synthesis of Ta3N5 NTs usually starts from the growth of Ta2O5 NTs by anodization, which is commonly used in growing other metal oxide nanotubes such as TiO2 nanotubes [25][26][27] .…”

“…Although better adhesion was reported later by using less concentrated HF in the electrolyte 30 , obtaining long and stable Ta2O5 NTs was still challenging. In recent years, Ta2O5 NTs grown by anodization in a concentrated H2SO4 and NH4F(aq) mixture have shown good stability and high aspect ratio, and the nanotubes were preserved after high temperature nitridation in NH3 gas environment in order to obtain Ta3N5 NTs 17,18,21,31 . A photocurrent density as high as 7.5 mA/cm 2 was obtained for Ba-doped Ta3N5 NTs decorated with Co-Pi (cobalt phosphate) as the co-catalyst 31 .…”