Noncovalent hybrid of CoMn₂O₄ spinel nanocrystals and poly (diallyldimethylammonium chloride) functionalized carbon nanotubes as efficient electrocatalysts for oxygen reduction reaction

We have grown CoMn₂O₄ spinel nanocrystals on poly (diallyldimethylammonium chloride) functionalized carbon nanotubes (PDDA-CNTs) by noncovalent functionalization and solvothermal techniques. PDDA plays an important role in homogeneously increasing the surface density of available functional groups, which can provide active sites for decoration of CoMn ₂O₄ on CNTs. In addition, PDDA preserves the intrinsic properties of CNTs, increases the active sites of catalysts, and enhances the durability of the catalysts. Here, CoMn₂O₄ nanocrystals were uniformly deposited on PDDA-CNTs with loading amounts from 36% to 83%. The as-prepared CoMn₂O₄/PDDA-CNT catalyst showed high current densities for the oxygen reduction reaction (ORR) in alkaline and neutral conditions, which outperformed the Co₃O₄/PDDA-CNT and Pt/C catalysts at medium overpotential, mainly through a 4e reduction pathway. The obtained CoMn₂O₄/PDDA-CNT hybrid exhibited excellent activity and durability when subjected to an oxygen evolution reaction. These results indicate that the CoMn₂O₄/PDDA-CNT hybrid represents a promising alternative to Pt for ORR electrocatalysis, and this non-precious bifunctional electrocatalyst provides a corrosion resistant and protective cathode layer to fuel cells. The excellent activity and stability of the hybrid materials demonstrate the potential of noncovalent coupling inorganic/carbon composites as novel catalytic systems for lithium-air batteries and chlor-alkali production.