On-Chip Electrical Transport Investigation of Metal Nanoparticles: Characteristic Acidic and Alkaline Adsorptions Revealed on Pt and Au Surface.

Metal nanocrystals have been extensively explored as efficient and tailorable electrocatalysts for various sustainable energy technologies. Precise understanding of molecular interactions at the electrode-electrolyte interfaces during electrochemical processes, which mostly relies on the interpretation of spectroscopic surface information, is crucial to the innovations in catalyst design and optimization of reaction conditions. Here, we demonstrate the first electrical transport evidence of pH-dependent surface anionic adsorptions on metal nanoparticles (MNPs), enabled by the on-chip electrical transport spectroscopy (ETS) of continuous nanoparticle (NP) thin films. Our results on platinum and gold NPs reveal the significant (and distinct) impacts of acid-base environments on their surface adsorption features, which contributes to the further understanding of gold- and platinum-based electrocatalytic systems. The successful employment of ETS on metal nanoparticles achieves a more general transport-based signaling technique that conveniently fits the abundance of catalytic materials with zero-dimension morphology.