Hierarchically porous nitrogen-doped graphene-NiCo₂O₄ hybrid paper as an advanced electrocatalytic water-splitting material

Abstract

In this work, we report a three-dimensional (3D) oxygen evolution reaction (OER) catalyst with hierarchical pores for water splitting. The remarkable features of well-developed in- and out-of-plane pores, 3D conductive networks, and N-doping have greatly promoted the transport in electrodes and assured high catalytic efficiency. The 3D hybrid paper of N-doped graphene–NiCo₂O₄ has shown a remarkable OER catalytic activity that was comparable to that of previously reported noble metal catalysts (IrO₂). The catalytic process occurred with favorable kinetics and strong durability. The dual-active-site mechanism is responsible for the excellent performance of the hybrid catalyst; that is, the edges of NiCo₂O₄and the N (O)–metal (Ni or Co) bonds are both active sites. This study affords a new strategy to achieve optimal performance in 3D catalysts, which may be extended to the preparation of other 3D hybrid materials for a broad range of technological applications.