Abstract
The higher methanol utilization efficiency in direct methanol fuel cell (DMFC) is one of the key factors that determine the performance of DMFC. Herein, we have synthesized bimetallic PtCo nano-particles (with optimized Pt:Co ratio) decorated reduced graphene oxide (rGO) nano-composite as anode catalyst. The electrochemical response of optimized PtCo (1:9)/rGO catalyst revealed efficient oxidation of 5 M methanol in half-cell configuration with ~ 60% Faradaic efficiency. A current density of 463.5 mA/cm2 and a power density of 136.8 mW/cm2 were achieved using PtCo (1:9)/rGO anode catalyst in a complete DMFC set-up at 100 °C with 5 M methanol supply which is ~ three times greater as compared to commercial Pt/C (48.03 mW/cm2). The low activation energy of 9.88 kJ/mol indicates the faster methanol oxidation reduction (MOR) kinetics of PtCo (1:9)/rGO anode catalyst. Furthermore, the higher methanol utilization and open-circuit voltage in complete DMFC using PtCo (1:9)/rGO as compared to commercial Pt/C indicate the reduced methanol crossover. The excellent catalytic behavior of PtCo (1:9)/rGO towards MOR and high methanol utilization warrant its potential application as anode catalyst in DMFC.
Highlights
Direct methanol fuel cells (DMFCs) are the promising source of green and affordable energy which directly converts chemical energy into electrical energy [1]
It could be clearly seen that PtCo nano-particles in PtCo (1:9)/reduced graphene oxide (rGO) composite are uniformly and densely distributed onto rGO sheets compared to Pt and PtRu nano-particle on carbon support indicating higher loading of PtCo (1:9) on rGO sheets that would contribute to higher catalytic performance
The smaller size and dense distribution of PtCo nano-particles onto rGO sheets is attributed to the anchoring site provided by defects in rGO for metal ions during the synthesis process; both these parameters are critical in achieving improved activity and stability of the catalyst [21]
Summary
Direct methanol fuel cells (DMFCs) are the promising source of green and affordable energy which directly converts chemical energy into electrical energy [1]. Methanol is considered as an attractive organic fuel due to its high power density (theoretical power density of 6100 Wh/kg at 25 °C, 30–40 times compared to Li-ion battery), low exhaust, and low operating temperatures [2, 3]. DMFC suffers from sluggish reaction kinetics of methanol oxidation at the anode. To attain maximum utilization efficiency and minimum platinum usage, the ultrafine Pt–M (M=Co, Ni, Cr, Pd, and Rh) alloys having large surface area with maximum active sites are proposed. The agglomeration and Ostwald’s ripening of nano-particles may lead to deterioration in stability and activity of these alloys [7].
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