Structural Evolution of Anatase-Supported Platinum Nanoclusters into a Platinum-Titanium Intermetallic Containing Platinum Single Atoms for Enhanced Catalytic CO Oxidation

CO-Assisted Methane Oxidation into Oxygenates over Surface Platinum-Titanium Alloyed Layers

Methane oxidation using molecular oxygen remains a grand challenge in which the obstacle is not only the activation of methane but also the reaction with oxygen, considering the mismatch of the ground spin states. Herein, we report TiO2-supported Pt nanocrystals (Pt/TiO2) with surface Pt-Ti alloyed layers that directly convert methane into oxygenates by using O2 as the oxidant with the assistance of CO. The oxygenate yield reached 749.8 mmol gPt-1 in a H2O aqueous solution over 0.1% Pt/TiO2 under 31 bar of mixed gas (20:5:6 CH4:CO:O2) at 150 °C for 3 h, while the CH3OH selectivity was 62.3%. On the basis of the control experiments and spectroscopic results, we identified the surface Pt-Ti alloy as the active sites. Moreover, CO promoted the dissociation of O2 on the surface of Pt-Ti alloyed layers and the subsequent activation of CH4 to form oxygenated products.

Significance of Epitaxial Growth of PtO2 on Rutile TiO2 for Pt/TiO2 Catalysts

TiO2-supported Pt species have been widely applied in numerous critical reactions involving photo-, thermo-, and electrochemical-catalysis for decades. Manipulation of the state of the Pt species in Pt/TiO2 catalysts is crucial for fine-tuning their catalytic performance. Here, we report an interesting discovery showing the epitaxial growth of PtO2 atomic layers on rutile TiO2, potentially allowing control of the states of active Pt species in Pt/TiO2 catalysts. The presence of PtO2 atomic layers could modulate the geometric configuration and electronic state of the Pt species under reduction conditions, resulting in a spread of the particle shape and obtaining a Pt/PtO2/TiO2 structure with more positive valence of Pt species. As a result, such a catalyst exhibits exceptional electrocatalytic activity and stability toward hydrogen evolution reaction, while also promoting the thermocatalytic CO oxidation, surpassing the performance of the Pt/TiO2 catalyst with no epitaxial structure. This novel epitaxial growth of the PtO2 structure on rutile TiO2 in Pt/TiO2 catalysts shows its potential in the rational design of highly active and economical catalysts toward diverse catalytic reactions.

Electronic Phosphide-Support Interactions in Carbon-Supported Molybdenum Phosphide Catalysts Derived from Metal-Organic Frameworks

Interfacial interaction in carbon-supported catalysts can offer geometric, electronic, and compositional effects that can be utilized to regulate catalytically active sites, while this is far from being systematically investigated in carbon-supported phosphide catalysts. Here, we proposed a novel concept of electronic phosphide-support interaction (EPSI), which was confirmed by using molybdenum phosphide (MoP) supported on nitrogen-phosphorus codoped carbon (NPC) as a model catalyst (MoP@NPC). Such a strong EPSI could not only stabilize MoP in a low-oxidation state under environmental conditions but also regulate its electronic structure, leading to reduced dissociation energy of the oxygen-containing intermediates and enhancing the catalytic activity for oxidative desulfurization. The removal of dibenzothiophene over the MoP@NPC was as high as 100% with a turnover frequency (TOF) value of 0.0027 s-1, which was 33 times higher than that of MoP without EPSI. This work will open new avenues for the development of high-performance supported phosphide catalysts.