Using operando X-ray absorption spectroscopy
in a continuous-flow
microfluidic cell, we have investigated the nucleation of platinum
nanoparticles from aqueous hexachloroplatinate solution in the presence
of the reducing agent ethylene glycol. By adjusting flow rates in
the microfluidic channel, we resolved the temporal evolution of the
reaction system in the first few seconds, generating the time profiles
for speciation, ligand exchange, and reduction of Pt. Detailed analysis
of the X-ray absorption near-edge structure and extended X-ray absorption
fine structure spectra with multivariate data analysis shows that
at least two reaction intermediates are involved in the transformation
of the precursor H2PtCl6to metallic platinum
nanoparticles, including the formation of clusters with Pt–Pt
bonding before complete reduction to Pt nanoparticles.