Photocatalytic Deacon Reaction over SrTiO₃

Abstract

SrTiO3 was prepared by a polymeric precursor method and applied in the photocatalytic aerobic oxidation of HCl in a flat‐plate reactor equipped with a UV LED array (368 nm). Reaction rates up to 240 mmol h−1 m−2 and apparent quantum yields up to 33 % using an illuminated area of 60 cm−2 were achieved with highly crystalline SrTiO3 calcined at 750 °C, outperforming commercially available SrTiO3 by a factor of almost 2. A gradual catalyst deactivation was observed, which was due to the formation of crystalline SrCl2×2 H2O on the surface confirmed by X‐ray diffraction, electron microscopy and X‐ray photoelectron spectroscopy (XPS). Increasing the HCl partial pressure accelerated both Cl2 formation and catalyst deactivation. XP spectra revealed an intrinsic surface segregation of Sr and the presence of several Sr‐ or O‐containing surface species. High Cl2 yields up to 42 % obtained with an illuminated area of 120 cm−2 encourage further research on a photocatalytic Deacon process for improved HCl recycling.

Mechanistic understanding of the thermal-assisted photocatalytic oxidation of methanol-to-formaldehyde with water vapor over Pt/SrTiO3

“…Photocatalytic methanol oxidation in the gas phase STO-based photocatalysts are widely employed in various (photocatalytic) reactions. [33][34][35][36] Here, the thermal-assisted methanol oxidation in the gas phase has been performed using 0.1Pt/STO that was previously shown to be most active in methanol conversion and highly selective for formaldehyde formation. 9 Extensive material characterization using N 2 physisorption measurements (BET method), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), inductively coupled plasma optical emission spectroscopy (ICP-OES), high resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDX) confirmed the phase purity of STO and successful deposition of Pt NPs.…”

The Influence of the Reaction Conditions on the Photocatalytic Gas‐Phase Conversion of Methanol with Water Vapor over Pt/SrTiO3 in a Continuously Operated Flow Reactor

“…A higher UV light intensity led to a higher X MeOH and lower AQY following a logarithmic dependence as observed before. [19,39] This behavior can be explained by the increased concentration of photogenerated charge carriers in SrTiO 3 which led to a high X MeOH , while simultaneously charge carrier recombination was accelerated. Additionally, the observed curves may be flattened due to kinetic limitations at high light intensity.…”

“…Strontium titanate (SrTiO 3 ) is a versatile photoabsorber, which is frequently applied in various photocatalytic applications such as overall water splitting [ 17 ] or selective alcohol oxidation [ 18 ] in the liquid phase. Recently, SrTiO 3 has been successfully used in gas‐phase HCl oxidation, [ 19 ] but gas‐phase oxidation of methanol using SrTiO 3 ‐based photocatalysts has not yet been reported. The structure of undoped SrTiO 3 samples as well as the electronic properties are well understood.…”

Non‐Classical Conversion of Methanol to Formaldehyde

“…The catalyst is spray‐coated on a sand‐blasted quartz‐glass plate with a standard loading of 5 mg cm −2 on an illuminated area of 60 cm 2 and equipped to the aluminum flat‐plate reactor (Fig. 7), which is similar to the one we used before 101, 102. The quartz glass window at the top site of the reactor allows the illumination of the catalyst layer by 30 LEDs ( λ = 368 nm, I = 56.08 mW cm −2 , Nichia NCSU275 UV‐SMD) arranged on an area of 60 cm 2 (Fig.…”