Abstract
For a safe environment, humanity should be oriented towards renewable energy technology. Water splitting (WS), utilizing a photoelectrode with suitable thickness, morphology, and conductivity, is essential for efficient hydrogen production. In this report, iridium oxide (IrO
x
) films of high conductivity were spin-cast on glass substrates. FE-SEM showed that the films are of nanorod morphology and different thicknesses. UV-Vis spectra indicated that the absorption and reflectance of the films depend on their thickness. The optical band gap (
E
g
) was increased from 2.925 eV to 3.07 eV by varying the spin speed (SS) of the substrates in a range of 1.5 × 10
3
–4.5 × 10
3
rpm. It was clear from the micro-Raman spectra that the films were amorphous. The
E
g
vibrational mode of Ir–O stretching was red-shifted from 563 cm
−1
(for the rutile IrO
2
single crystal) to 553 cm
−1
. The IrO
x
films were used to develop photoelectrochemical (PEC) hydrogen production catalysts in 0.5M of sodium sulfite heptahydrate Na
2
SO
3
·
7H
2
O (2-electrode system), which exhibits higher hydrogen evaluation (HE) reaction activity, which is proportional to the thickness and absorbance of the used IrO
x
photocathode, as it showed an incident photon-to-current efficiency (
IPCE
%) of 7.069% at 390 nm and −1 V. Photocurrent density (
Jph
= 2.38 mA/cm
2
at −1 V vs. platinum) and PEC hydrogen generation rate (83.68 mmol/ h cm
2
at 1 V) are the best characteristics of the best electrode (the thickest and most absorbent IrO
x
photocathode). At −1 V and 500 nm, the absorbed photon-to-current conversion efficiency (
APCE
%) was 7.84%. Electrode stability, thermodynamic factors, solar-to-hydrogen conversion efficiency (
STH
), and electrochemical impedance spectroscopies (EISs) were also studied.