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.
Room‐temperature sodium–sulfur (RT Na–S) batteries are among the ideal candidates for grid‐scale energy storage due to their high theoretical energy density. However, rapid dissolution of polysulfides along with extremely slow redox kinetics lead to a low practical cell capacity and inferior cycling stability, inhibiting their practical applications. Herein, an innovative design strategy is introduced for a chemical and structural synergistic immobilization of sodium‐polysulfides in the cathode structure. An aluminum oxyhydroxide (AlOOH) nanosheets decorated sulfur/carbon black nanocomposite (S@CB@AlOOH) is used as an efficient cathode material for stable RT Na–S batteries. The cathode material exhibits extremely stable cycling performance, delivering an initial specific capacity of 392 mA h g–1 and retains 378 mA h g–1 after 500 cycles at 1C. The excellent performance is attributed to the synergistic effect of the structural encapsulation as well as chemical immobilization of polysulfides, significantly suppressing their gradual dissolution into liquid electrolyte. Density functional theory (DFT) calculations reveal that through favorable Lewis acid–base interactions, AlOOH catalyzes the redox conversion of the higher‐order polysulfides (Na2Sn, 6 ≤ n ≤ 8) to the lower‐order polysulfides (Na2Sx, 1 ≤ x ≤ 2). The importance of Lewis acid–base catalysis to enhance the overall performance of these batteries is demonstrated.
Li–O2 batteries are considered as one of the
promising beyond Li-ion battery technologies owing to their high energy
density. But, their poor cycle life due to sluggish oxygen reduction
reaction (ORR) and oxygen evolution reaction (OER) hinder the commercialization
of this technology. Hence, fabrication of highly efficient ORR and
OER catalysts is of paramount importance in order to improve the cyclic
stability and longevity of this device. Herein, we discuss systematically
the synthesis and electrochemical analysis of such bifunctional perovskite
catalysts, namely, pristine CaMnO3 and its defect induced
counterpart. When evaluated as a cathode catalyst in a Li–O2 battery along with a redox mediator LiI, the oxygen deficient
CaMnO3 gives an improved cycle life reported at a high
current rate of 500 mA g–1 with a capacity of 500
mA h g–1 in comparison with similar catalysts reported
in the literature. Introduction of defects in the pristine framework
predominantly improves the catalytic activity by lowering the overpotential.
The presence of oxygen vacancies creates mixed-valence states of Mn3+/Mn4+ which modify the electronic structure, resulting
in the improved catalytic activity. Comprehensive phase and compositional
analysis confirm the formation of the desired defect-induced structure
with improved catalytic activity toward ORR and OER which is elaborated
with electrochemical analysis.
Increasing environmental pollution, shortage of efficient energy conversion and storage devices and the depletion of fossil fuels have triggered the research community to look for advanced multifunctional materials suitable for different energy-related applications. Herein, we have discussed a novel and facile synthesis mechanism of such a carbon-based nanocomposite along with its energy and environmental applications. In this present work, nitrogen-doped carbon self-assembled into ordered mesoporous structure has been synthesized via an economical and environment-friendly route and its pore generating mechanism depending on the hydrogen bonding interaction has been highlighted. Incorporation of metal oxide nanoparticles in the porous carbon network has significantly improved CO2 adsorption and lithium storage capacity along with an improvement in the catalytic activity towards Oxygen Reduction Reaction (ORR). Thus our present study unveils a multifunctional material that can be used in three different fields without further modifications.
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