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The interaction between metal particles and the oxide support, the so-called metal–support interaction, plays a critical role in the performance of heterogenous catalysts. Probing the dynamic evolution of these interactions under reactive gas atmospheres is crucial to comprehending the structure–performance relationship and eventually designing new catalysts with enhanced properties. Cobalt supported on TiO2 (Co/TiO2) is an industrially relevant catalyst applied in Fischer−Tropsch synthesis. Although it is widely acknowledged that Co/TiO2 is restructured during the reaction process, little is known about the impact of the specific gas phase environment at the material's surface. The combination of soft and hard X-ray photoemission spectroscopies are used to investigate in situ Co particles supported on pure and NaBH4-modified TiO2 under H2, O2, and CO2:H2 gas atmospheres. The combination of soft and hard X-ray photoemission methods, which allows for simultaneous probing of the chemical composition of surface and subsurface layers, is one of the study's unique features. It is shown that under H2, cobalt particles are encapsulated below a stoichiometric TiO2 layer. This arrangement is preserved under CO2 hydrogenation conditions (i.e., CO2:H2), but changes rapidly upon exposure to O2. The pretreatment of the TiO2 support with NaBH4 affects the surface mobility and prevents TiO2 spillover onto Co particles. [ABSTRACT FROM AUTHOR]

3D printing is presented as an auspicious additive manufacturing technique for diverse interesting applications coupling electrochemistry and spectroscopy techniques, proposing as utilities: a general-purpose module for specular spectroscopy and spectroelectrochemical (SEC) cells for in situ UV-VIS and Raman measures capable of acting in flux or a stationary regime. As a proof of concept, UV-VIS absorption and middle-infrared spectra of an azo dye thin film were collected with the specular module showing characteristic bands according to the literature data. SEC investigations related to the Prussian Blue (PB) film growth on the platinum electrode surface were also investigated. By applying appropriate potentials, the PB film growth was accompanied by a proportional increase in the absorption signal at 700 nm in the UV-VIS region. This signal was related to the intervalence charge transfer from the Fe(II)-C to Fe(III)-N. Moreover, the Raman SEC experiment presented scattering intensity at 2092 and 2156 cm-1, related to the (CN) mode associated with the Fe(II) and Fe(III) cations, which was observed during the thin film growth. In addition, the conversion to the Berlin Green (BG) and Prussian White (PB) forms was monitored while applying the suitable potential and in situ spectroscopic observations of structural changes during the redox processes were also detected as described in the literature. Thus, it is possible to state that the accessories successfully validated in situ spectroelectrochemical dynamic investigations unlocking many other applications in this research field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface activity of dyes is a key parameter for photocatalytic wastewater treatment. • Dynamic surface tension of Malachit Green (MG) and Eriochrom Black-T (EBT) show strong dependency to pH. • Novel characterization method is introduced for interactions of the catalyst nanoparticle with dye molecules based on dynamic surface properties analysis. • Photocatalytic wastewater treatment can be improved considering pollutants-catalyst interactions via dynamic surface tension and interfacial elasticity analysis. In photocatalytic processes for wastewater treatment, the degradation reactions mainly occurs at the surface of the catalyst and nearby regions. Therefore, understanding of the interactions between the catalyst and pollutant in a photocatalytic degradation system is of utmost importance, determining the affinity of the pollutant molecules to be attracted or repulsed from the photocatalyst particles. The aim of this experimental study is to get a better insight about the interactions between the catalyst nanoparticles and pollutant molecules via a novel characterization method based on dynamic surface phenomena analysis. Drop profile analysis tensiometry (PAT) is used for this purpose for dynamic surface tension and elasticity measurements of dye solutions (as pollutants), and in mixed solutions with catalyst particles at different pH conditions. The results demonstrate that the cationic dye Malachit Green (MG) has a low surface activity at pH 6.5, with an equilibrium surface tension about 69 mN/m. While it becomes much more surface active at pH 9 and surface tension is decreased to 59 mN/m. Adding TiO 2 nanoparticles to MG solution at pH 9 causes a significant increase in surface tension, with much slower dynamics of adsorption at air/water interface. These results indicate a significant attraction and attachment of MG molecules to the surface of TiO 2 nanoparticles, creating MG-TiO 2 complexes, which have mobility much slower than the free MG molecules. This observation is in a good correlation with observed higher efficiency of MG degradation around pH 9. The capability of this novel experimental protocol is also examined for the anionic dye Eriochrom Black-T (EBT). According to the results, a significant interaction between TiO 2 nanoparticles and EBT exist at pH 3, which is also well in accordance with reported higher efficiency of EBT degradation around pH 3. The elasticity measurements performed in this work, also support these results as an important characterization parameter for estimation of the molecular interactions in mixed adsorbed layers. [ABSTRACT FROM AUTHOR]