Optimizing the synergy between alloy and alloy-oxide interface for CO oxidation in bimetallic catalysts

Revealing Dynamics and Competitive Mechanism of Gas-Induced Surface Segregation of PdFe0.08 Dilute Alloy by Multi-Dimensional Imaging

The restructuring of dilute alloys under gas environments has shown a great impact on their catalytic performance due to intriguing structural sensitivity, but the structural dynamics and underlying mechanism remains elusive. Herein, we directly resolved the distinct dynamic behaviors of PdFe0.08 dilute alloys under CO or O2 environment by multidimensional imaging. The stronger binding of gaseous CO with Fe atoms stimulates Fe segregation out of the PdFe0.08, resulting in 3D growth of Fe islands, whereas the dissociative adsorption of O2 results in 2D layer-by-layer growth of segregated FeO as encapsulation overlayers that bind strongly with the Pd surface underneath. Such varied structures remarkably tune the catalytic activity for CO oxidation, showing a considerably high activity for a CO-treated sample. Our results reveal the competitive mechanism between adsorbate-metal and metal-metal interaction for gas-induced surface segregation, which should be highly considered for the rational design of dilute alloys with dynamically tuned structure and reactivity.

Hydrogen Spillover Induced PtCo/CoOx Interfaces with Enhanced Catalytic Activity for CO Oxidation at Low Temperatures in Humid Conditions

The development of catalysts with abundant active interfaces for superior low-temperature catalytic CO oxidation is critical to meet increasingly rigorous emission requirements, yet still challenging. Herein, this work reports a PtCo/CoOx/Al2O3 catalyst with PtCo clusters and enriched Pt─O─Co interfaces induced by hydrogen spillover from the Pt sites and self-oxidation process in air, exhibiting excellent performance for CO oxidation at low temperatures and humid conditions. The combination of structural characterizations and in situ Fourier transform infrared spectroscopy reveals that the PtCo cluster effectively prevents CO saturation/poisoning on the Pt surface. Additionally, the presence of Pt─O─Co interfaces in the PtCo/CoOx/Al2O3 catalyst provides a significant number of active sites for oxygen activation and ─OH formation. This facilitates efficient generation of CO2 at ambient temperature by coupling with nearby adsorbed CO molecules, resulting in superior low-temperature activity and long-term stability for CO oxidation under humid conditions. This work provides a facile route toward rationalizing the design of catalysts with more active interfaces for superior low-temperature CO oxidation under humid conditions for practical applications.

Synergistic interface between metal Cu nanoparticles and CoO for highly efficient hydrogen production from ammonia borane

The development of efficient non-noble metal catalysts for the dehydrogenation of hydrogen (H2) storage materials is highly desirable to enable the global production and storage of H2 energy. In this study, Cu x -(CoO)1-x /TiO2 catalysts with a Cu-CoO interface supported on TiO2 are shown to exhibit high catalytic efficiency for ammonia borane (NH3BH3) hydrolysis to generate H2. The best catalytic activity was observed for a catalyst with a Cu : Co molar ratio of 1 : 1. The highest dehydrogenation turnover frequency (TOF) of 104.0 molH2 molmetal -1 min-1 was observed in 0.2 M NaOH at room temperature, surpassing most of the TOFs reported for non-noble catalysts for NH3BH3 hydrolysis. Detailed characterisation of the catalysts revealed electronic interactions at the Cu-CoO heterostructured interface of the catalysts. This interface provides bifunctional synergetic sites for H2 generation, where activation and adsorption of NH3BH3 and H2O are accelerated on the surface of Cu and CoO, respectively. This study details an effective method of rationally designing non-noble metal catalysts for H2 generation via a metal and transition-metal oxide interface.