Normalization of the EOR catalytic efficiency measurements based on RRDE study for simply fabricated cost-effective Co/graphite electrode for DAEFCs

Abstract

• Facile fabrication of low-cost and highly efficient Co/graphite electrocatalyst for direct alkaline ethanol fuel cells (DAEFC). • RRDE study for effective distinction between EOR and OER processes. • Normalized parameters for reliable measuring EOR catalytic efficiency. For the catalytic oxidation of ethanol (EtOH), Co is chronoamperometricaly deposited on graphite (G) from 0.05 M CoCl 2 solution with an optimum potential of −1.1 V for 1000 s. The optimum produced Co/G (opt.) electrode yields an ethanol oxidation onset potential (Et-E onset ) 1.43 V/RHE and a current density, I at 1.6 V/RHE = 26.58 mA.cm −2 at a scan rate of 50 mV.s -1 . Its cyclic voltammetry (CV) and rotating ring-disc (RRDE) responses, in solutions of 0.5 M NaOH without and with 1 M EtOH, show the priority of ethanol oxidation reaction (EOR) rather than the oxygen evolution reaction (OER) or transformation of CoOOH to CoO 2 in the potential range 1.4 ≤ E ≤ 1.8 V/RHE. The RRDE responses are used to distinguish between EOR and OER currents in presence of ethanol. The present study includes sincere efforts to resolve the controversy about the measurement of the ethanol oxidation activity parameters. In addition, Co/G (opt.) electrode shows remarkable activity and stability for OER in absence of EtOH. Its overpotential required to achieve 10 mA.cm −2 ( η t = 0 ) is 0.38 V; while, after 24 h, (η t=24h ) is 0.40 V. These values are a noteworthy outcome for our easy and straightforward fabrication method for such an efficient EOR/OER electrocatalyst expending low-cost materials when compared with the previously published work.