Modulating the surface defects of titanium oxides and consequent reactivity of Pt catalysts

Resolving the Effect of Oxygen Vacancies on Co Nanostructures Using Soft XAS/X-PEEM

Improving both the extent of metallic Co nanoparticle (Co NP) formation and their stability is necessary to ensure good catalytic performance, particularly for Fischer–Tropsch synthesis (FTS). Here, we observe how the presence of surface oxygen vacancies (O_vac) on TiO₂ can readily reduce individual Co₃O₄ NPs directly into CoO/Co⁰ in the freshly prepared sample by using a combination of X-ray photoemission electron microscopy (X-PEEM) coupled with soft X-ray absorption spectroscopy. The O_vac are particularly good at reducing the edge of the NPs as opposed to their center, leading to smaller particles being more reduced than larger ones. We then show how further reduction (and O_vac consumption) is achieved during heating in H₂/syngas (H₂ + CO) and reveal that O_vac also prevents total reoxidation of Co NPs in syngas, particularly the smallest (∼8 nm) particles, thus maintaining the presence of metallic Co, potentially improving catalyst performance.

Enhancing electronic metal support interaction (EMSI) over Pt/TiO2 for efficient catalytic wet air oxidation of phenol in wastewater

Phenol is one of the major hazardous organic compounds in industrial wastewater. In this work, a highly active Pt/TiO₂ catalyst for catalytic wet air oxidation (CWAO) of phenol was obtained by supporting pre-synthesized Pt on TiO₂. During the followed hydrogen reduction, strong hydrogen spillover occurred without the migration of TiO₂ onto Pt. The reduced support then enhanced the electron transfer from TiO₂ to Pt, increasing the percentage of partially negative Pt (Pt^δ-), which has been confirmed by XPS. The strong EMSI made the obtained catalyst far more active than Pt/TiO₂ prepared by impregnation method. The electron-enriched Pt/TiO₂ achieved total organic carbon (TOC) conversion of 88.8% and TOF 149 h^-1 at 100 °C and 2 MPa O₂, while conventional Pt/TiO₂ gave TOC conversion of 39.5% and TOF 41 h^-1 for CWAO of phenol. Our work indicates that the enhancement of EMSI between metal and support can be an effective approach to develop highly active catalysts for phenol treatment.

Highly selective generation of singlet oxygen from dioxygen with atomically dispersed catalysts

Singlet oxygen (1O2) as an excited electronic state of O2 plays a significant role in the ubiquitous oxidative processes from enzymatic oxidative metabolism to industrial catalytic oxidation. Generally, 1O2 can...

Tuning the shape and crystal phase of TiO2 nanoparticles for catalysis

Synthesis of TiO₂ nanoparticles with tunable shape and crystal phase has attracted considerable attention for the design of highly efficient heterogeneous catalysts. Tailoring the shape of TiO₂, in the crystal phases of anatase, rutile, brookite and TiO₂(B), allows tuning of the atomic configurations on the dominantly exposed facets for maximizing the active sites and regulating the reaction route towards a specific channel for achieving high selectivity. Moreover, the shape and crystal phase of TiO₂ nanoparticles alter their interactions with metal species, which are commonly termed as strong metal-support interactions involving interfacial strain and charge transfer. On the other hand, metal particles, clusters and single atoms interact differently with TiO₂, because of the variation of the electronic structure, while the surface of TiO₂ determines the interfacial bonding via a geometric effect. The dynamic behavior of the metal-titania interfaces, driven by the chemisorption of the reactive molecules at elevated temperatures, also plays a decisive role in elaborating the structure-reactivity relationship.