Synergistic Interaction of Cobalt Carbodiimide Flakes on Oxidized Carbon Nanotubes for Enhanced Electrocatalytic Oxygen Reduction

Transition metal-nitrogen-carbon (M–N–C) based catalysts have shown great promise as an alternative to platinum group metals for the oxygen reduction reaction (ORR). However, the complex coordination environments of different active centers make it challenging to achieve a precise understanding of the structure-function relationships in M–N–C based catalysts. Herein, we developed transition metal carbodiimides with unambiguously characterized M–N–C moieties and large M–M interatomic distances as promising ORR electrocatalysts. Crystalline CoNCN flakes with preferential exposure of (100) facets were supported on oxidized carbon nanotubes (O-CNTs), which assisted charge redistribution around Co centers. The obtained CoNCN/O-CNT electrocatalyst displayed a catalytic activity comparable to that of commercial Pt/C catalysts and good long-term stability with the attenuation of only 6 mV in half-wave potential after 20000 cyclic voltammetry cycles. Quasi in situ X-ray emission and absorption spectroscopy experiments confirmed the structural stability of the Co–N–C motifs during electrocatalysis. These results offer an ideal material system for understanding the structure-function correlation between well-defined M–N–C moieties and ORR activity.