Nitrogen-assisted electroless assembling of 3D nanodendrites consisting of Pd and N-doped carbon nanoparticles as bifunctional catalysts

Abstract

We report a facile synthesis of three-dimensional (3D) nanodendrites of Pd nanoparticles (NPs) and nitrogen-doped carbon NPs (N-CNPs) by electroless deposition of Pd²⁺ ions. N-CNPs being an electron-enriched material act as a reducing agent. Moreover, the availability of a variety of nitrogen species in N-CNPs promotes the open arm structure as well as stabilizes the oriented 3D assembly of primary Pd NPs. The dendrites exhibit superior catalytic activity for methanol (0.5 M) oxidation in alkaline media (1 M NaOH) which is ascribed to the large electrochemical active surface area and the enhanced mass activity with repeated use. Further mass activity improvement has been realized after acid-treatment of dendrites which is attributed to the increment in the –OH group. The dendrites show higher mass activity (J_f ∼ 653 A g⁻¹) in comparison with a commercial Pt–carbon/Pd–carbon (Pt–C/Pd–C) catalyst (J_f ∼ 46 and 163 A g⁻¹, respectively), better operational stability, superior CO tolerance with I_f/I_b (∼3.7) over a commercial Pt–C/Pd–C catalyst (I_f/I_b ∼ 1.6 and 1.75, respectively) and may serve as a promising alternative to commercial Pt–C catalysts for anode application in alkaline fuel cells. To ensure the adaptability of our 3D-nanodendrites for other catalytic activities, we studied 4-nitrophenol reduction at room temperature. The 3D-nanodendrites show excellent catalytic activity toward 4-nitrophenol reduction, as well.