Surface Plasmon Resonance Effect of Noble Metal (Ag and Au) Nanoparticles on BiVO4 for Photoelectrochemical Water Splitting

Abstract

Photoelectrochemical (PEC) splitting water technology over the years has gradually matured, and now photoanodes loaded with nanoparticles (NPs) show excellent PEC performance. Each of the metal NPs has a different effect on the PEC performance of BiVO4. This work selected the noble metals Ag and Au to modify BiVO4 and study its PEC performance. After recombination, the photocurrent densities of Ag/BiVO4 and Au/BiVO4 photoanodes were 3.88 mA/cm2 and 1.61 mA/cm2 at 1.23 VRHE, which were 3.82 and 1.72 times that of pure BiVO4. The hydrogen evolution of pure BiVO4 is about 1.10 μmol·cm−2. Ag/BiVO4 and Au/BiVO4 contain 3.56 and 2.32 times pure BiVO4, respectively. Through the research, it was found that the composite noble metal (NM) NPs could improve the PEC properties; this is because NM NPs can introduce a surface plasmon resonance (SPR) effect to increase the concentration and accelerate the separation of carriers. The mechanism of the SPR effect can be explained as NM NPs are excited by light generating “hot electrons”, and the hot electrons can directly enter the conduction band (CB) of BiVO4 through an electron transfer mechanism. The potential energy of the Schottky barrier generated by the contact of NM NPs with BiVO4 is smaller than that generated by the SPR effect, which enables the “hot electrons” to be smoothly transferred from the NM NPs to the conduction band of BiVO4 without returning to the NM NPs. Ag/BiVO4 showed higher PEC activity than Au/BiVO4 because of its higher light absorption, photocurrent, and oxygen evolution capacity. It can be seen that loading NM NPs increases the concentration of the carriers while the separation and transfer rates of the carriers are improved. In conclusion, it was concluded from this study that the loading of NM NPs is an effective method to improve the water oxidation kinetics of BiVO4 photoanodes.