Raman Spectroscopic Data of the Quenching Phases of a Pt Solution in a Low Water Reduced Carbonic Fluid at P = 200 and T = 950–1000°C

Abstract

Raman spectroscopic data of quenching phases in experiments on the dissolution of Pt in reduced carbonic fluid, containing about 30 mol % of CO, both with and without chlorine at P = 200 MPa and T = 950–1000°C are presented. Water content in the fluid was no more than 4.5 mol %. The only soluble form of Pt determined in the acetone solution of the quenching phases and in the experimental products is platinum carbonyl. Low concentrations of carbonyl (no more than a few ppm) become detectable using Raman spectroscopy due to the SERS effect (Surface-Enhanced Raman Scattering), which is possible in the presence of Pt nanoparticles in the objects under study. Platinum nanoparticles, formed at the decomposition of carbonyls, generates specific photoluminescence (PL) peak approximated by Gaussian with parameters FWHM = 1050–1300 cm^–1, k_max = 2050–2100 cm^–1 both in acetone solution and experimental samples. The spectra of CO (main band k ≈ 2050 cm^–1) adsorbed on Pt nanoparticles supported on glassy carbon, formed during the decomposition of excess CO relative to the CCO buffer, corresponded to nanoparticle sizes of about 2 nm. No convincing evidence of a mixed chloride-carbonyl composition of platinum was found in the spectra, which may reflect the lower thermodynamic stability of these mixed complexes at high P-T parameters. Large concentrations of platinum Pt on carbon (up to 2000–3000 ppm) can be explained by the formation of the Pt-C matrix bond and the weakening of the Pt-CO bond in carbonyls, causing their decomposition. Unusual PL peaks were detected in samples from experiments with chlorine-containing fluids, very reminiscent of the PL background of noble metal nanoparticles and attributed to the effect of carbon nanoparticles.