Reduction of hexachloroplatinate(IV) ions with methanol under UV radiation

• PtCl62− ions were photoreduced with CH3OH to PtCl42− and then to Pt nanoparticles.
• The reaction order with respect to CH3OH initial concentration is equal to 2.
• The reaction order with respect to PtCl62− initial concentration is equal to 1.
• The reaction order with respect to light intensity is equal to 1.
• Formaldehyde is the main product of methanol oxidation.

The aim of presented study was the detailed spectroscopic characterization of the mechanism of the photoreduction of hexachloroplatinate(IV) with methanol. The reaction mixture was illuminated at 375 nm and it was shown that PtCl62− ions were reduced with methanol to PtCl42− only in the presence of light. In the dark, methanol did not reduce hexachloroplatinate(IV) at the room temperature. Formaldehyde was the main product of methanol oxidation. Subsequently, PtCl42− ions were photoreduced to metal. Growth of Pt nanoparticles occurred in the dark. Kinetic studies have shown that the process was first order with respect to both PtCl62− initial concentration and light intensity and second order with respect to methanol initial concentration. Observed rate constant of the PtCl62− reduction with methanol, from illuminated solution, decreased with increasing PtCl62− initial concentration.