Fabricating Dispersed Fine Silver Nanoparticles on Liquid Substrate for Improved Photocatalytic Water Splitting Efficiency

Abstract

Dispersed silver nanoparticles (NPs) are synthesized on a silicone oil substrate under varied substrate temperature T by thermal vaporization method. Scanning electron microscopic investigation demonstrates that the mean size of the NPs are around 7.8 nm with a standard deviation of 1.0 nm. The NPs are transferred to a strontium titanate (STO) crystal as co-catalyst for water splitting efficiency test. The photoelectrochmical (PEC) measurement reveals the photocatalytic activity of NP co-catalyst sensitively relies on T during deposition process: the relative current density jr increases from 4.8 μA/cm2 to 25.4 μA/cm2 as T goes up from 253 K to 333 K. However, a slight decrease of jr from 25.4 μA/cm2 to 22.8 μA/cm2 is found as T further increases to 353 K. The dependent behavior of jr on T is explained in term of a competition mechanism between microstructure evolution and growth model of the NPs under different T: for T ranging from 253 K to 333 K, the effect of a higher crystalline structure for NPs fabricated under higher T improves the electron transfer rate from STO to NPs is dominant. As T increases to 353 K, the overlapping of NPs become a factor for photocatalytic activity of NP/STO system: the diffusion distance of electrons becomes larger and the apparent contact area between NPs and STO is reduced which in turn reduce the photocatalytic activity of NP/STO. The experimental method to synthesize NPs in this report may open up a way to further apply fine NPs in enhancing photocatalytic water splitting efficiency.