Revealing structure–activity links in hydrazine oxidation: doping and nanostructure in carbide–carbon electrocatalysts

Abstract

To expand the range of hydrazine oxidation catalysts active in alkaline pH – a key challenge in fuel cell electrocatalysis – we studied the effect of doping on carbide–carbon composites. Pyrolysis of organometallic precursors based on Fe–M cores (M = Fe/Zn/Cu) yielded Fe₃C-embedded, N-doped, hierarchically porous, graphitic carbons. These multi-doped materials showed excellent hydrazine oxidation activity (onset 0.28 V vs. RHE at pH = 14). Doping enhanced activity by nanostructural effects, rather than purely catalytic effects, as revealed by electrochemical and material investigations (XRD, XPS, SEM, TEM, Raman and N₂ porosimetry). Zinc and copper boosted microporosity in the carbons by two different mechanisms – either gas phase etching by Zn_(g) vapors, or enhanced exfoliation of well-dispersed Cu_(s) nanoparticles upon reaction with acid.