Conduction and Valence Band Positions of Ta₂O₅, TaON, and Ta₃N₅ by UPS and Electrochemical Methods

Abstract

The conduction and valence band edges for electronic band gaps and Fermi levels are determined for Ta2O5, TaON, and Ta3N5 by ultraviolet photoelectron spectroscopy (UPS) and electrochemical analyses. Reasonable agreement between the results of the two methods is obtained at the pH at which the ζ potentials of the particles are zero. The tops of the valence bands are found to be shifted to higher potential energies on the order Ta2O5 < TaON < Ta3N5, whereas the bottoms of the conduction bands are very similar in the range −0.3 to −0.5 V (vs NHE at pH = 0). From the results, it is concluded that TaON and Ta3N5 are promixing catalysts for the reduction and oxidation of water using visible light in the ranges λ < 520 nm and λ < 600 nm, respectively. It is also demonstrated that the proposed UPS technique is a reliable alternative to electrochemical analyses for determining the absolute band gap positions for materials in aqueous solutions that would otherwise be difficult to measure using electrochemical methods.

Optoelectronic properties ofTa3N5: A joint theoretical and experimental study

“…IIID) as well as previous experimental findings using UV-Vis data. 3,30,31 This parameter was fixed because it is the first feature, correlates with the Tauc-Lorentz oscillator occurring at a peak transition energy of ∼ 4 eV and agrees with previous literature findings. 30,46 Furthermore, the next transition occurring at E g = 2.44 also agrees with the BSE/G 0 W 0 optical spectra (shown in Figs.…”

From Cu2S nanocrystals to Cu doped CdS nanocrystals through cation exchange: controlled synthesis, optical properties and their p-type conductivity research

“…S6), with benefits for their potential applications in luminescent solar concentrators (LSCs) and bio-imaging [41,42]. UPS is a convincible way to determine the valence band and Fermi level positions of semiconductors [43,44]. The energy band diagrams of the as-prepared Cu 2 S and Cu doped CdS NC films were determined by UPS and UVVis absorption measurements (Figs 5 and 6).…”

Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency

“…The energy bands of Ta 3 N 5 straddle the water redox potentials 19 21)), having a conduction band too positive for H 2 evolution. Ta 3 N 5 has been widely used for both photocatalytic and PEC water splitting [22][23][24][25][26][27][28] .…”