Abstract
The integration of polymer electrolyte membrane fuel cell (PEMFC) stack into vehicles necessitates the replacement of high-priced platinum (Pt)-based electrocatalyst, which contributes to about 45% of the cost of the stack. The implementation of high-performance and durable Pt metal-free catalyst for both oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) could significantly enable large-scale commercialization of fuel cell–powered vehicles. Towards this goal, a simple, scalable, single-step synthesis method was adopted to develop palladium-cobalt alloy supported on nitrogen-doped reduced graphene oxide (Pd3Co/NG) nanocomposite. Rotating ring-disk electrode (RRDE) studies for the electrochemical activity towards ORR indicates that ORR proceeds via nearly four-electron mechanism. Besides, the mass activity of Pd3Co/NG shows an enhancement of 1.6 times compared to that of Pd/NG. The full fuel cell measurements were carried out using Pd3Co/NG at the anode, cathode in conjunction with Pt/C and simultaneously at both anode and cathode. A maximum power density of 68 mW/cm2 is accomplished from the simultaneous use of Pd3Co/NG as both anode and cathode electrocatalyst with individual loading of 0.5 mg/cm2 at 60 °C without any backpressure. To the best of our knowledge, the present study is the first of its kind of a fully non-Pt based PEM full cell.
Highlights
In recent years, the rate of depletion of fossil fuel reserves is elevating in a rapid speed due to high demand of energy
Single cell measurements revealed that the prepared electrocatalyst has both good hydrogen oxidation reaction (HOR) activity and oxygen reduction reaction (ORR) activity
No separate peaks corresponding to cobalt can be seen in the X-ray diffraction (XRD) pattern which confirms the formation of palladium-cobalt alloy[21]
Summary
The rate of depletion of fossil fuel reserves is elevating in a rapid speed due to high demand of energy. Though PGM-free catalysts like transition metal-nitrogen-carbon (TM-N-C) based composite have proved to exhibit good ORR activity, most of the studies have shown ORR activity of TM-N-C using electrochemical half-cell measurements[5]. Researchers have already extensively reported carbon nanomaterials like carbon black, carbon nanotubes, graphene, carbon nanofibres as supporting materials for anchoring catalyst nanoparticles in PEMFC16–20. Among these carbon materials, graphene has proved as an excellent support material due to various reasons like high surface area, good electrical conductivity and good mechanical and chemical stability in operating environment[21,22,23,24]. Qu et al demonstrated nitrogen-doped graphene is a good metal free electrocatalyst in fuel cell[30]. Single cell measurements revealed that the prepared electrocatalyst has both good hydrogen oxidation reaction (HOR) activity and oxygen reduction reaction (ORR) activity
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