Nonscalable oxidation catalysis of gold clusters

Area of Science:

• * Nanomaterials Science
• * Catalysis
• * Surface Chemistry

Background:

• * Small, negatively charged gold (Au) clusters can activate molecular oxygen (O2) for carbon monoxide (CO) oxidation in vacuum.
• * This suggests potential for Au clusters as aerobic oxidation catalysts, but precise control over structural parameters like size and composition is crucial due to their strong influence on intrinsic chemical properties.
• * Developing Au cluster oxidation catalysts faces challenges in achieving this precise structural control.

Purpose of the Study:

• * To describe efforts in the precision synthesis of small (diameter <2 nm) gold clusters.
• * To stabilize these clusters using polymers and immobilize them on supports for diverse catalytic applications.
• * To leverage the intrinsic, size-specific chemical nature of Au clusters for advanced catalysis.

Main Methods:

• * Preparation of small Au clusters weakly stabilized by polyvinylpyrrolidone (PVP).
• * Size control of Au:PVP clusters using a microfluidic device and monitoring via mass spectrometry.
• * Development of methods for precise size and composition control of supported Au clusters using ligand-protected precursors.
• * Immobilization of Au clusters on mesoporous silica, hydroxyapatite, and carbon nanotubes.

Main Results:

• * Au clusters smaller than a critical size demonstrated various aerobic oxidation reactions.
• * Proposed mechanism involves catalytic activation of O2 by negatively charged Au clusters.
• * Demonstrated an optimal Au cluster size for cyclohexane oxidation.
• * Achieved significant improvement in Au25 cluster oxidation catalysis via single-atom Palladium (Pd) doping.
• * Showcased non-scalable catalysis of Au clusters, highlighting potential beyond bulk counterparts.

Conclusions:

• * Precisely controlled sub-2 nm gold clusters exhibit unique aerobic oxidation catalytic properties.
• * Size and composition are critical parameters dictating the catalytic performance of gold clusters.
• * Novel catalytic functionalities can be achieved by reducing catalyst size to the sub-2 nm regime, opening avenues for new catalytic applications.