WO3, Pt-loaded SrTiO3:Rh (Pt/SrTiO3:Rh), and Pt-loaded
CuAlGaO4 (Pt/CuAlGaO4) were employed as the O2-photocatalyst,
H2-photocatalyst, and CO2-photocatalyst, respectively. The solidstate
fusion method, which was used to synthesized SrTiO3:Rh
and CuAlGaO4 photocatalysts, was described thoroughly in
previous studies [26,28]. For SrTiO3:Rh, powders of SrCO3, TiO2,
and Rh2O3 were well mixed in the molar ratio of
Sr:Ti:Rh = 1:0.99:0.01 and pulverized in a mortar with CH3OH to
well disperse the mixed powders. After that, the resulting powder
was calcined at 1300 C for 10 h, and then cooled to room temperature
and further pulverized to obtain SrTiO3:Rh. Similar procedure
has been employed for the preparation of CuAlGaO4. Here, CuO,
Al2O3, and Ga2O3 powders were firstly mixed in the molar ratio
of Cu:Al:Ga = 1:1:1 and pulverized in a mortar. Subsequently, the
resulting mixture was calcined at 1150 C for 12 h, and then cooled
to room temperature and further pulverized to obtain CuAlGaO4.
Platinum (Pt) was loaded on either SrTiO3:Rh or CuAlGaO4 by the
photo-deposition method as described in the same reference. The
required amount of H2PtCl6 solution was mixed with SrTiO3:Rh
and CuAlGaO4 powder, respectively. The loading of Pt on
SrTiO3:Rh is 0.8 wt% while that on CuAlGaO4 is 1 wt%. The mixed
solution was irradiated by an UV source (200W mercury arc lamp,
Exfo S1500) for 1.5 h to perform the photo-deposition process.
After that, the solid product was centrifuged and washed by DI
water several times to ensure that there was no residual Cl on
the material. Finally, the washed material was dried at 80 C in
an oven to obtain Pt/SrTiO3:Rh and Pt/CuAlGaO4 powders. The
WO3 (99.9%) photocatalyst, which is supplied from