Preparation and characterization of noble metal (Pt, Ag, Ru) loaded ZnGa₂O₄ and its photocatalytic and photoelectric performance

ZnGa₂O₄ nanoparticles were prepared by hydrothermal method. Noble metal (Pt, Ag, Ru) nanoparticles were subsequently selected as cocatalyst for ZnGa₂O₄ surface modification by photo-deposition method. XRD, SEM, TEM, HRTEM, UV–vis DRS and PL techniques were used for crystalline structure, morphology, composition, light absorption and charge separation analysis, respectively. The deposition of cocatalyst (Pt, Ag, Ru) enhanced the visible light absorption and improved the electrons and holes separation. The photocatalysts were investigated in the photocatalytic reduction of CO₂ with H₂O containing NaOH and Na₂SO₃ as sacrificed agent under the simulated sunlight irradiation. The highest photocatalytic efficiency was observed over 1 wt% Pt/ZnGa₂O₄, and the yield of the main reduction products, methanol, was 3.72 mmol g_cat ⁻¹ under 120 min light irradiation, which was 4.3 times as compared to the unloaded ZnGa₂O₄. The photoelectric properties of ZnGa₂O₄ and 1 wt% Pt/ZnGa₂O₄ samples were also detected. The transient photocurrents of 1 wt% Pt/ZnGa₂O₄ sample are remarkably higher than that of unloaded ZnGa₂O₄. A possible mechanism of photocatalytic reduction of CO₂ over Pt/ZnGa₂O₄ was proposed.