CoPtnanoparticles and their catalytic properties in electrooxidation of CO and CH3OH studied by in situ FTIRS

Abstract

CoPt nanoparticles supported on a glassy carbon electrode (denoted as CoPt/GC) were prepared by galvanic replacement reaction between electrodeposited Co nanoparticles and K₂PtCl₆ solution. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were both employed to characterize the CoPt nanoparticles. It was shown that the CoPt nanoparticles have irregular shapes and most of them exhibit a core-shell structure with a porous Co core and a shell of Pt tiny particles. The composition of the CoPt nanoparticles was analyzed by energy-dispersive X-ray spectroscopy (EDX), which depicts a Co : Pt ratio of ca. 21 : 79. Studies of cyclic voltammetry (CV) demonstrated that CoPt/GC possesses a much higher catalytic activity towards CO and methanol electrooxidation than a nanoscale Pt thin film electrode. In situ FTIR spectroscopic studies have revealed for the first time, that a CoPt nanoparticles electrode exhibits abnormal IR effects (AIREs) for IR absorption of CO adsorbed on it. In comparison with the IR features of CO adsorbed on a bulk Pt electrode, the direction of the IR bands of CO adsorbed on the CoPt/GC electrode is inverted completely, and the intensity of the IR bands has been enhanced up to 15.4 times. The AIREs is significant in detecting the adsorbed intermediate species involved in electrocatalytic reactions. The results demonstrated a reaction mechanism of CH₃OH oxidation on CoPt/GC in alkaline solutions through evidencing CO_L, CO_M, HCOO⁻, CO₃²⁻, HCO₃⁻ and CO₂ as intermediate and product species by in situ FTIRS.