Proposed molecular mechanism for the colloidal nanocatalysis of the hexacyanoferrate III–thiosulfate electron transfer reaction: On the involvement of a Prussian blue analogue complex intermediate

Attenuated total reflectance (ATR-FTIR) spectroscopic methods were used to study the mechanism of the reaction between hexacyanoferrate III (HCFIII) and thiosulfate catalysed, by colloidal platinum nanostar (PtNSs). A dynamic flow cell was fabricated and used for in situ FTIR and optical measurements for the reaction near zero-time after mixing the reacting materials. It is proposed here that the mechanism of this reaction takes place via a Prussian blue analogue complex intermediate, whereby the HCFIII reacts with the PtNS surface atoms prior to reacting with the thiosulfate reactant. Further, it is proposed here that the complex occurs on the PtNSs surface and that platinum atoms move through multiple redox cycles as they are oxidized and reduced by the reactants. When the reaction is complete, the Pt atoms largely return to their ground state through reduction by excess thiosulfate in solution. In this way, the majority of the Pt atoms are thought to remain associated with the same nanoparticle throughout the reaction, thus providing evidence for a heterogeneous particle surface mediated nanocatalysis.