Aims: In this study, the photocatalytic hydrogen evolution reaction from aqueous methanol
was investigated upon simulated solar light using platinum loaded on cobalt doped TiO2 (Pt/Co-TiO2)
Background: Controversial results of cobalt-based composites create doubts about their photocatalytic
activity. Thus, cobalt doped TiO2 composites were synthesized differently, and the photocatalytic
activity was examined for the photocatalytic hydrogen generation.
Objective: The current study aims to investigate the influence of cobalt doping and platinum loading
on the photocatalytic activities of TiO2 nanoparticles for the photocatalytic H2 generation.
Methods: The 0.5 wt.% Co-TiO2 and bare TiO2 photocatalysts were synthesized using two different
methods, namely, reflux and hydrothermal synthesis. Additionally, the Pt deposition on the prepared
Co-TiO2 and TiO2 catalysts (1 wt.% Pt) was performed using a photo-platinization method.
The as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy/
energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), ultraviolet-
visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), electron paramagnetic
resonance (EPR), and electrochemical impedance spectroscopy (EIS).
Results: The XRD and EPR studies clearly indicated that the Co was incorporated into the titanium
dioxide lattice. The EIS results suggested that the reduction of protons over Co-TiO2 and bare TiO2
materials was possible from a thermodynamic point of view. However, the photocatalytic results revealed
that the formed amount of H2 was extremely low and close to the detection limit. The evolution
of H2 from aqueous methanol (10 vol%) showed higher rates when employing 1 wt.% Pt loaded on
0.5 wt.% Co-TiO2 photocatalysts under simulated solar light irradiation. A maximum of 317 ± 44
μmol.h-1 was observed over the Pt/Co-TiO2-HT photocatalyst.
Conclusion: EPR results confirmed that the cobalt ions were introduced into the TiO2 lattice by trapping
the photogenerated conduction band electrons and decreasing the defects in the crystal cell. The
Mott−Schottky analysis of electrochemical impedance measurements showed that all catalysts were ntype
semiconductors and that cobalt doping induces impurity level within the band gap of TiO2. The
experimental results of photocatalytic H2 generation from methanol-reforming demonstrated that no
significant impact of Co-doping on the photocatalytic H2 formation was observed neither for bare
TiO2 samples nor for the platinized materials. Based on these experimental findings, a possible mechanism
for the continuous photocatalytic activity of Pt/Co-TiO2 photocatalysts under simulated solar
light was proposed.