Green functionalization of carbon supports with Coscinium fenestratum extract for enhanced Pt nanocatalysts in direct formic acid oxidation

The synthesis and performance evaluation of platinum (Pt) nanocatalysts supported on carbon materials modified with Coscinium fenestratum (Gaertn.) Colebr. Extract ( C. fenestratum) for enhanced electrocatalytic activity in formic acid oxidation were studied. Multi-walled carbon nanotubes (CNT), functionalized CNT (FCNT) and carbon black (CB) served as support materials, with Pt nanoparticles deposited via chemical reduction. The plant extract introduced nitrogen-containing functional groups, as confirmed by FT-IR and XPS analyses, while Raman spectroscopy indicated increased structural defects favorable for Pt anchoring. TEM revealed uniform Pt dispersion, and XRD confirmed crystalline Pt with increased disorder in the carbon supports. Electrochemical testing in 0.5 M H 2 SO 4  + 0.5 M HCOOH demonstrated that Pt catalysts on extract-modified carbons (Pt/Extract-Carbon) outperformed both commercial Pt/C and unmodified Pt/Carbon catalysts, showing lower onset potentials, higher peak current densities, and improved specific and mass activities. Notably, Pt/Extract-CNT exhibited the best performance in terms of activity, stability, and resistance to aggregation, attributed to enhanced metal-support interactions and nitrogen doping. The modified catalysts also showed lower Tafel slopes and charge transfer resistance (R ct ), indicating superior kinetics and catalytic pathways. These findings underscore the potential of C. fenestratum -modified carbon materials as sustainable, high-performance supports for Pt-based electrocatalysts in direct formic acid fuel cells.