Promoting formic acid and ethylene glycol electrooxidation activity on Ga modified Pd based catalysts

Abstract

Herein, carbon nanotube (CNT)-supported Ga@PdAgCo catalysts were synthesized by sodium borohydride (SBH) sequential reduction method. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS). Characterization results revealed that these catalysts were succesfully preared at desired loading and atomic ratios. From the XRD pattern, the crystallite size of 0.5% Ga@PdAgCo(80:10:10)/CNT catalysts was found as 6.95 nm by utilizing the Scherrer equation. From TEM measurements, the average particle sizes of Pd/CNT, PdAgCo(80:10:10)/CNT, and 0.5% Ga@PdAgCo(80:10:10)/CNT catalysts were found to be 54 nm, 25 nm, and 7 nm, respectively. It is clear that particle sizes obtained from TEM and XRD were close to eachother. Electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and cyclic voltammetry (CV) measurements were realized to examine the formic acid and ethylene glycol electrooxidation performances of catalysts. 0.5% Ga@PdAgCo(80:10:10/CNT) and 7% Ga@PdAgCo(80:10:10/CNT) catalysts had the best specific activity and mass activity as 3.37 mA/cm2 (297.61 mA/mg Pd) and 4.95 mA/cm2 (462.59 mA/mg Pd) for ethylene glycol and formic acid electrooxidation, respectively. In addition, EIS results showed that Ga@PdAgCo(80:10:10/CNT) catalyst had a faster electron transfer rate via low charge transfer resistance. As a result, 0.5% Ga@PdAgCo(80:10:10/CNT) catalyst is a promising new anode catalyst for direct ethylene glycol fuel cells.