Engineering fully exposed edge-plane sites on carbon-based electrodes for efficient water oxidation

Abstract

Endowing metal-free graphitic carbon electrodes with high electrocatalytic reactivity is a field of intense research, but remains elusive. Here, we introduce a prototypical edge-plane-site-specific engineering strategy on “herringbone” multi-walled carbon nanotubes by performing an intercalation-exfoliation and truncation process in molten inorganic salts. Controllable synthesis of the target H-MWCNTs-MS with fully exposed edge-plane sites on both the outer surface and inner channels was demonstrated. in-situ infrared spectroscopic study supports the theoretically energetic “edge-state” and identifies the reconstructed ketone/carboxyl-terminated edge sites under oxygen evolution reaction (OER) conditions. These oxygenated edge-plane sites boost charge redistribution and interlayer coupling, which essentially govern the synergistic catalysis, as evidenced by combined theoretical, electrokinetic, and H/D isotopic studies. Benefiting from the dense reactive sites and efficient electron tunneling, the H-MWCNTs-MS demonstrated impressive OER activity with an overpotential of 236 mV at a current density of 10 mA cm−2 in alkaline media, outperforming most state-of-the-art metal-free electrocatalysts reported to date. Furthermore, the catalyst displayed no noticeable degradation during 100 h of operation, indicating its potential for practical applications.