Double Perovskite LaFe1-xNixO3 Coated with Sea Urchin-like Gold Nanoparticles Using Electrophoresis as the Photoelectrochemical Electrode to Enhance H2 Production via Surface Plasmon Resonance Effect.

The surface plasmon resonance (SPR) effect and the hetero-junction structure play crucial roles in enhancing the photocatalytic performances of catalysts for the water-splitting reaction. In this study, a series of double perovskites LaFe1-xNixO3 was synthesized. LaFe1-xNixO3 particles were then decorated with sea urchin-like Au nanoparticles (NPs) with the average size of approximately 109.83 ± 8.48 nm via electrophoresis. The d-spacing became narrow and the absorption spectra occurred the redshift phenomenon more when doping increasing Ni mole concentrations for the raw LaFe1-xNixO3 samples. From XPS analysis, the Ni atoms were inserted into the lattice of the matrix, resulting in the defect of the oxygen vacancy, and NiO and Fe2O3 were formed. This hybrid structure was the ideal electrode for photoelectrochemical hydrogen production. The photonic extinction of the Au-coated LaFe1-xNixO3 was less than 2.1 eV (narrow band gap), and the particles absorbed more light in the visible region. According to the Mott-Schottky plots, all the LaFe1-xNixO3 samples were the n-type semiconductors. Moreover, all the band gaps of the Au-coated LaFe1-xNixO3 samples were higher than 1.23 eV (H+/H2). Then, the hot electrons from the Au NPs were injected via the SPR effect, the coupling effect between LaFe1-xNixO3 and Au NPs, and the more active sites from Au NPs into the conduction band of the semiconductor, improving the hydrogen efficiency. The H2 efficiency of the Au-coated LaFe1-xNixO3 measured in ethanol was approximately ten times larger than the that of Au-coated LaFe1-xNixO3 measured in 1-butanol at any testing temperature because ohmic and kinetic losses occurred in the latter solvent. Thus, the activation energies of ethanol at any testing temperature were smaller. The maximum real H2 production was up to 43,800 µmol g-1 h-1 in ethanol. The redox reactions among metal ions, OH*, and oxides were consecutively proceeded under visible light illumination.