Integrated in situ RGB colorimetry and redox potential monitoring as a strategy for controlled synthesis of platinum nanostructures

Controlling the kinetics of liquid phase synthesis is essential to elucidate transformation mechanisms and tailoring the properties of precious metal nanoparticles (NPs) and nanostructured materials. This study examines the formation kinetics of Pt NPs and supported Pt/C materials via the reduction of H2PtCl6 using formic (FA), citric (CA), and ascorbic (AA) acids. It also analyzes the structural, morphological, and electrochemical properties of the resulting materials. A key innovation is the validation of a novel approach that complements standard methods by combining RGB colorimetry with in-situ monitoring of the reaction medium's redox potential, specifically, open-circuit potential (OCP). This inexpensive technique provides data with accuracy and reliability comparable to established methods such as UV–vis spectroscopy, etc. The research identified distinct kinetic features of the Pt(IV) → Pt(0) transformation for each acid. Significant kinetic differences were observed, with NPs formation time decreasing in the order: FA > CA >> AA. Conversely, the electrochemically active surface area and catalytic activity for oxygen electroreduction increased in the order: AA << FA < CA. Owing to their superior structural characteristics, the Pt/C materials synthesized with citric acid demonstrated a higher electrochemical surface area and greater activity than a conventional commercial catalyst.