Kinetics and Optimization of Hexagonal Palladium Nanosheets: Unveiling Insights into CO-Mediated Synthesis Strategies and Mechanistic Understanding.

Nanoparticles with unique shapes and structures have attracted significant attention due to their distinctive properties and potential applications, but their growth mechanism is often overlooked. Hexagonal palladium nanosheets (HPNS) were synthesized through a CO-mediated reduction approach. Herein, we investigate the kinetics of the HPNS formation and modify the experimental conditions consistently by changing the carbon monoxide (CO) precursor, temperature, and stirring speed. The CO precursor plays a major role in HPNS formation with an emphasis on the kinetics of the release of CO in the solution. Slow-release and atmosphere CO precursors resulted in the highest shape yield of HPNS relative to tetrahedrons, while the fast-release CO precursor leads to the formation of a higher percentage of tetrahedrons. Additionally, an increase of the addition temperature of the CO precursor and a higher stirring rate were found to improve the shape yield of the HPNS, leading to an optimized synthetic strategy of the HPNS at high shape yield. Kinetics of the reaction with a slow-release CO precursor provided insights into the formation mechanism of the HPNS and suggested an aggregative model with an interplay between reduction kinetics and the thermodynamic stability of HPNS relative to the tetrahedrons.