Synergetic effect of Ni and Au nanoparticles synthesized on titania particles for efficient photocatalytic hydrogen production

• Bimetallic Au/Ni-NiO NPs by gamma radiolysis on TiO2 for photocatalytic H2 production.
• Enhanced H2 evolution rate obtained for TiO2 co-modified with Au and Ni-NiO.
• Observation of a synergetic effect between Au and Ni-NiO.
• 3 steps of photocatalytic mechanism studied by absorption, TRMC and action spectra.
• Bimetallic nanoparticles act as recombination sites for atomic H conversion to H2.

Au and/or Ni nanoparticles were synthesized by radiolysis on TiO2 (commercial P25) at various composition (metal content). The modified photocatalysts were characterized by High Resolution Transmission Microscopy (HRTEM), Energy-Dispersive X-ray Spectroscopy (EDS), UV–vis Diffuse Reflectance Spectroscopy (DRS) and X-ray Photoelectron Spectroscopy (XPS). The charge-carrier mobility was studied by Time Resolved Microwave Conductivity (TRMC). The photocatalytic activities were tested under UV–vis irradiation using polychromatic and monochromatic light (action spectrum analysis of apparent quantum efficiency). Surface modified TiO2 with Au and Ni nanoparticles showed high photocatalytic activity for hydrogen evolution from aqueous methanol solution. The enhanced hydrogen evolution rate was obtained for TiO2 co-modified with Au and Ni, where synergetic effect of the two metals was revealed. A very small amount of gold associated to nickel (atomic ratio Ni:Au 5:1 with a total optimized metal loading of 0.5 at%) can induce a significant increase in H2 formation.

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