In Situ Pt Photodeposition and Methanol Photooxidation on Pt/TiO₂: Pt-Loading-Dependent Photocatalytic Reaction Pathways Studied by Liquid-Phase Infrared Spectroscopy

Abstract

We developed a top-irradiated, liquid-phase attenuated total reflectance Fourier transform infrared (ATR-FTIR) setup that allows time-resolved investigations of both Pt particle growth during in situ photodeposition via monitoring of the Pt 0 −CO ads band on TiO 2 thin films as well as the photooxidation of methanol in aqueous environments. Obtained ATR-FTIR data sets were analyzed via multivariate curve resolution-alternating least squares (MCR-ALS), which enabled us to clearly differentiate various reaction pathways for different Pt loadings at otherwise fixed reaction conditions (i.e., methanol concentration, UV intensity). At the highest Pt loading (nominal concentration of 2.7 wt %), photooxidation of methanol occurs via direct oxidation through a formaldehyde intermediate to CO 2 , whereas the lower Pt loadings of 0.7 and 1.4 wt % favor a side reaction that includes methyl formate as an intermediate. These findings were correlated with the formation of different CO binding sites on Pt during photodeposition, and we presume that changes in the reaction pathway depend on the number rather than the nature of active available Pt sites. Complementary ex situ characterizations of the thin films by transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were performed, delivering information on the generated Pt nanoparticles and structural changes of TiO 2 . The presented optical setup paves the way for fundamental studies of heterogeneous catalytic reactions as close as possible to their actual use in aqueous systems.

Photo-assisted sequential assembling of uniform metal nanoclusters on semiconductor support

“…methods. Compared with other works ( Toledo-Camacho et al., 2021 ; Al-Madanat et al., 2021 ; Galeano et al, 2019 ; Diak et al., 2015 ; Haselmann et al., 2020 ), the i.d. method adopted in this paper can realize the deposition of high loading amount and uniform sub-nano noble metal particles on TiO 2 .…”

Selective ligand removal to improve accessibility of active sites in hierarchical MOFs for heterogeneous photocatalysis

“…The relatively large band gap of MIL of 3.6 eV mandates the use of a UV light source for fair activity comparison 50 . Pt was added as a co-catalyst via in situ photodeposition 51 , 52 . TEM images reveal that the Pt nanoparticles are predominantly located on the surface of the MOF particles and that neither their average size of ~2 nm nor their dispersion has noticeably changed during the HER reaction (Supplementary Fig.…”

In‐Situ Observation of the Formation of NiSi/Ni2Si Heterojunction in SiGe Nanowire with Al2O3 Diffusion Barrier Layer

“…Ni silicides have gained the considerable importance for their favorable chemical stability, low resistance, low work function, high process compatibility, and low formation temperature. [8] In situ observation technique are used to conduct the experiments for real-time acquisition and analysis of materials during the reaction, such as in situ X-ray photoelectron spectroscopy, [9] in situ Fourier-transform infrared spectro scopy, [10] in situ surface-enhanced Raman spectroscopy, [11] in situ X-ray diffraction, [12] and in situ synchrotron transmission X-ray microscopy. [13] Among these techniques, in situ transmission electron microscopy (TEM) has the capability to obtain the dynamic information, such as diffusion, [14] crystal growth, [15] and phase transformation at nanoscale.…”