Enhancement of photocurrent response for self-ordered Nb2O5 nanotubes synthesized at room temperature

Abstract

The major challenge regarding new photocatalysts is to obtain a semiconductor with high and stable photocurrent from inexpensive and abundant materials. Niobium oxide meets some of these requirements, but its photocurrent is usually very low. Therefore, this study introduces the synthesis and characterization of self-organized Nb2O5 nanotubes (Nb2O5Nt) presenting a high photocurrent density of 0.04 mA cm−2 under incidence of artificial sunlight, of 100 mW cm−2, and potential of 1.5 V without further surface modification. The best catalyst was obtained through anodization of a Nb foil at 90 V for 2 h in a one-compartment and two-electrodes cell at room temperature, using glycerol, H2O, and NH4F as the electrolyte, followed by annealing at 450 °C for 60 min. The water concentration was the most important factor to obtain the desired morphology with a good distribution of nanotube diameters, high UV absorption, low bang gap (3.2 eV) compared to the observed for the Nb2O5 semiconductor (3.4 eV), and great photocurrent density. Such properties turn the Nb2O5Nt into a promising catalyst for direct use in photochemical reactions or as a good platform yet to be combined in heterojunctions or applied for doping and decoration.