Improving the Activity of Platinum Nanoparticles in Electrocatalytic Oxidation of Formic Acid via the Surface Grafting of Thiol or Thiophenol Molecules

Electrocatalytic oxidation of organic molecules, in particular the formic acid oxidation reaction (FAOR), is crucial for applications such as direct liquid fuel cells. As one of the effective catalysts, platinum (Pt) has been widely used as the electrocatalyst for these reactions in the laboratory; however, its utilization in practical FAOR is still limited due to insufficient activity. This study introduces a simple and rapid molecular modification method to improve the FAOR performance of Pt by chemically adsorbing thiol or thiophenol molecules. At an optimal surface coverage of 7.1%, the current density of FAOR on cysteamine-grafted Pt reached up to 24.76 mA cm^-2, a 7.2-fold increase compared to that on pristine Pt. This increase is mainly attributed to the change in the electronic structure of the Pt surface and the charge transfer at the interface, which are induced by the cysteamine molecules. X-ray photoelectron spectroscopy and in situ Raman spectroscopy demonstrated that the adsorption of cysteamine molecules on the Pt surface improves the charge transfer on the Pt surface and the production of formic acid via the formate pathway. The mechanism of enhanced catalysis on Pt-Cysteamine is revealed by density functional theory calculations. Interestingly, various thiols and thiophenols were also proved to be effective in promoting the FAOR reaction, and this strategy could also be applied to improve the performance of many other reactions (such as, methanol oxidation reaction).