Quantitative pinhole on-line electrochemical mass spectrometry study on ethanol electro-oxidation at carbon-supported Pt and Ir-containing catalysts

Abstract

Pinhole on-line Electrochemical Mass Spectrometry (POEMS) system was constructed by using a pinhole below ten micron covered with a Teflon film as gas inlet. The 20 wt% electrocatalysts with different molar ratio for platinum and iridium were synthesized by a modified polyol method. These catalysts were physically characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques. The electrocatalytic activity and reaction intermediates of Pt/C and PtIr/C electrocatalysts for the ethanol oxidation reaction (EOR) were investigated by potentiodynamic and potentiostatic techniques with ODEMS system. Faster kinetics for CO stripping on PtIr bimetallic alloys can be deduced that a ligand effect of Ir is operated on the Pt electronic structure. The potentiodynamic and potentiostatic tests for ethanol oxidation show that, although kinetics of the reaction is faster on Pt/C, PtIr/C electrocatalysts exhibit higher ethanol oxidation efficiency. The average CO2 current efficiency (CCE) was also determined on both electrocatalysts after calibration of the m/z = 44 signal: the CCE value can reach up to 15% on PtIr/C at room temperature, compared to ca. 7% on Pt/C, which proves the powerful ability of Ir for the CC bond breaking.