Vertically Oriented Ti–Pd Mixed Oxynitride Nanotube Arrays for Enhanced Photoelectrochemical Water Splitting

Abstract

In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium-palladium mixed oxynitride films via anodization of Ti-Pd alloy in an electrolyte solution of formamide containing NH(4)F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti-Pd oxynitride nanotube array films were utilized in solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm(2) and a ∼5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm(2), 1.0 M KOH) compared to pure TiO(2) nanotubes fabricated and tested under the same conditions. The obtained efficiency is among the highest reported values for a TiO(2) nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays.

Photoelectrocatalytic Glucose Oxidation to Promote Hydrogen Production over Periodically Ordered TiO2 Nanotube Arrays Assembled of Pd Quantum Dots

“…The peak interval between Pd 3d 3/2 and 3d 5/2 was 4.7 eV and the intensity ratio of Pd 3d 5/2 to Pd 3d 3/2 was 3/2, which was consistent with theoretical calculation. The presence of Pd 0 indicated that metallic Pd was deposited onto the surface of TNTAs, while the presence of Pd 2+ implied the existence of PdO, possibly from surface oxidation of Pd metal [18,30,34,35]. Besides, the XRD results showed that the diffraction peaks at 2u = 25.5 and 37.9 were assigned to the (1 0 1) and (0 0 4) planes of anatase TiO 2 , respectively (Fig.…”

10-fold enhancement in light-driven water splitting using niobium oxynitride microcone array films

“…Due to the high potential energy of the metal-nitrogen bond compared to the metal-oxygen bond, transition metal oxynitrides [9][10][11][12], are identified as an alternative class of materials that can efficiently be used for solar energy conversion. This difference in bond energy results in narrower band gap energies in oxynitrides compared to their metal oxide counterparts.…”

“…This difference in bond energy results in narrower band gap energies in oxynitrides compared to their metal oxide counterparts. In addition, oxynitrides are ideal photoelectrodes for water splitting applications due to their stability in alkaline media [9][10][11][12]. Among all studied oxynitrides, niobium oxynitride (NbON) showed a significant promise as a visible light responsive material with suitable bandedge positions for water splitting [13,14].…”

Study of plasmonics induced optical absorption enhancement of Au embedded in titanium dioxide nanohole arrays

“…Yet, relatively low solar utilization percentage of TiO 2 material remains a challenge due to its large band gap (3.2 eV for anatase and 3.0 eV for rutile). Researches have shown that introduction of defects or dopants into the TiO 2 lattice can extend the absorption spectrum of TiO 2 into visible light region [6][7][8][9].…”