Highly active and durable Pd nanoparticles-porous graphitic carbon nitride composite for electrocatalytic oxygen reduction reaction

• ORR activity of Pd-CNx catalyst is superior to Pt/C.
• Pd-CNx shows 60 mV positive E1/2 than Pt/C in basic medium.
• Stability of Pd-CNx is much higher than Pt/C or Pd/C in both acidic and basic medium.
• Pd and CNx interaction, lower d-band center of Pd can be attributed ORR activity.

The electrochemical oxygen reduction reaction (ORR) is a cathodic process of fuel cells. The carbon supported Platinum, Pt/C catalyst is universally used as cathode materials; but poor durability of Pt/C due to degradation of catalyst prevent its wide spread applications. It is thus important to develop new cathode material(s) with high activity and stability. We report here, superior electrocatalytic activity of palladium nanoparticles-carbon nitride (Pd-CNx) composite towards ORR in both alkaline and acidic media. The ORR activity on Pd-CNx catalyst is better (half wave potential E1/2 of 60 mV more positive) than that of Pt/C in 0.5 M KOH solution and is almost comparable in acid media. Moreover, this porous composite display excellent methanol tolerance and has much better long term durability than that of commercial Pt/C in both acidic and alkaline media. Only 4 and 6 mV positive shift of E1/2 after 1500 potential cycles in basic medium and acid media respectively prove the excellent durability of this catalyst. The superior electrocatalytic activity and excellent stability of porous Pd-CNx composite can be attributed to unique synergistic interaction between CNx support and Pd nanoparticles (Pd-NPs), lower the d-band center of Pd, easy mass transport, and surface structure of Pd-NPs.

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