Controllable synthesis of N-doped carbon nanohorns: tip from closed to half-closed, used as efficient electrocatalysts for oxygen evolution reaction

Abstract

The development of efficient, cost-effective and stable N-doped carbon material with catalytic activity as an excellent catalyst for the oxygen evolution reaction (OER) is critical for renewable energy systems. In this study, the unique tip-half-closed N-doped carbon nanohorns (THC-N-CNHs) were firstly produced by the positive pressure-assisted arc discharge method using N₂ as the nitrogen source. Benefitting from the novel tip-half-closed structure and sufficient porosity, the specific surface area (SSA) of THC-N-CNHs is calculated to be 670 m² g⁻¹ without any further treatment, which is three times larger than that of traditional tip-closed CNHs. More importantly, the content of nitrogen can achieve ∼1.98 at% with noticeable pyridinic-N enrichment, increasing the number of active sites for the OER. Furthermore, the three-dimensional spherical feature and the unique pore structure for THC-N-CNHs lead to the fast transportation of electrons, and facile release of the evolved O₂ bubbles during the OER process. Therefore, THC-N-CNHs exhibit excellent electrocatalytic activity toward the OER, with an overpotential of 328 mV at 10 mA cm⁻², which is superior to that of most N-doped carbon material-based electrocatalysts. Meanwhile, the resulting catalyst also shows excellent durability after long-term cycling. Finally, we emphasize that THC-N-CNHs can be promising candidates as cheap, industrially scalable catalytic scaffolds for OER application.