Surface properties of PtCdS and mechanism of photocatalytic dehydrogenation of aqueous alcohol

Abstract

Abstract The various factors influencing the photocatalytic dehydrogenation of acidic aqueous ethanol on treated PtCdS were systematically studied using X-ray photoelectron spectroscopy (XPS), spin trapping, X-ray diffraction (XRD), transmission electron microscopy (TEM), IR spectroscopy, photoacoustic spectroscopy (PAS), etc. The following conclusions can be drawn. (I) The photocatalytic dehydrogenation of aliphatic alcohols is mediated by the OH radical - the photo-oxidation product of H 2 O (2) From the energetics and reaction mechanism, a CdSCdOCd(OH) 2 layer must be formed on the surface of the PtCdS photocatalyst. (3) In acidic medium, the photoreduction product of PtCl 6 2− on CdS is PtS which can be converted to Pt 0 via high-temperature air treatment. Pt 0 traps electrons and catalyses the reduction of H + to H 2. . (4) The ·OH radical reacts quickly with the α-hydrogen atom of the alcohol producing inactive hydroxyalkyl radical, thus eliminating the corrosion of the CdS surface by ·OH. (5) Due to differences in the dipole moments, rupture energies of the α-CH bonds and steric factors of various alcohol molecules, their γ H2 values are different; the sequence is as follows: EtOH > MeOH ≈ n -PrOH ≈ n - BuOH > i-BuOH > t -BuOH ( = 0).