into a thin film on precleaned conductive fluorine-doped tin oxide
(FTO) glass (2.2 mm thick, Sigma-Aldrich) via an electrophoretic deposition
(EPD) process. Concisely, 20 mg of NdTiO2+xN1–x was dispersed in 30 mL of
acetone containing 10 mg of iodine by 20 min sonication to obtain
a uniform suspension. Two FTO slides were immersed into the suspension
parallelly with an ∼10 mm gap, and then a 35 V bias was applied
between them for 1 min. The FTO/NdTiO2+xN1–x photoanodes were dried naturally
in air.
A NbCl5 impregnation step, which was adapted
from TaCl5 and TiCl4,15 (link),23 (link) was performed to improve the connection of particles. The FTO/NdTiO2+xN1–x photoelectrode was soaked in 0.1 M NbCl5 (99.99 wt %,
abcr GmbH) dissolved in ethanol for 10 s and dried on a hot plate
at 423 K. After repeating this procedure for four rounds, the electrode
was then annealed in air at 573 K for 1 h to obtain FTO/NdTiO2+xN1–x/Nb2O5. The electrode was further decorated
with a water oxidation cocatalyst, i.e., CoOx. A 45 μL aliquot of 7 mM Co(NO3)2 dissolved in methanol was dropped on the FTO/NdTiO2+xN1–x/Nb2O5 surface followed by annealing at 473 K for 1 h. The
composite electrode was washed with distilled water.