Green synthesis of platinum nanoparticles as a robust electrocatalyst for methanol oxidation reaction: Metabolite profiling and antioxidant evaluation

Abstract

A novel, low-cost, and environmentally friendly method of synthesising biogenic platinum nanoparticles (Pt NPs) was employed using biomass sugar cane (Saccharum officinarum L.) bagasse extract (SBE) as the reducing agent. Pt NPs derived from this biosynthesis route were thoroughly characterised by High-resolution transmission electron microscopy (HRTEM), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the involvement of bio-reductive metabolites during biosynthesis, their metabolite profiles were identified using gas chromatography-mass spectrometry (GC-MS) and in-vitro antioxidant activities. Eleven major metabolite compounds from the SBE classified as phenol, pyrazole, furan, pyran, epoxide, long-chain fatty acid, sterol glycoside, and mixed oxygenated compounds may be responsible for the bio-reduction process. The biogenic Pt NPs endowed a high antioxidant property that can scavenge DPPH free radicals by 81.9%, with an inhibitory effect (IC50) of 37.60 μg/mL and ferric reducing antioxidant power assay (FRAP) of 57.58 μmol FeSO4/g. Furthermore, the biogenic Pt NPs deliver superior electrocatalytic activity in methanol oxidation reactions with tunable Pt ions concentration, PtCl62−, from 0.5 to 1.75 mM, with a maximum electrochemical active surface area (ECSA) of 93.41 m2 g−1 and a mass activity/specific activity of 581.50 mA mg−1/1.25 mA cm−2Pt, which is 3.67 times higher than that of commercial Pt black (158.12 mA mg−1). This study demonstrates that green chemical reduction using plant extracts is a viable method for producing biogenic Pt NPs for energy conversion and health applications, owing to its improved electrocatalytic activity and profound antioxidant properties.