Hierarchically Coupled Ni:FeOOH Nanosheets on 3D N-Doped Graphite Foam as Self-Supported Electrocatalysts for Efficient and Durable Water Oxidation

Here, a hierarchical nanostructure composed of Ni-doped alpha-FeOOH (Ni:FeOOH) nanosheets coupled with N-doped graphite foam (NGF) is demonstrated as a three-dimensional (3D) self-supported electrocatalyst for highly efficient and durable water oxidation. A facile, one-step directional growth of catalytically active Ni:FeOOH nanosheets on highly conducting 3D NGF results in a fully integrated, hierarchical, nanostructured electrocatalyst with (i) the high intrinsic activity of Ni:FeOOH, (ii) the outstanding electrical conductivity of NGF, and (iii) a well-defined porous structure with an enhanced active surface area. As a result, the self-supported 3D Ni:FeOOH/NGF electrocatalyst exhibits remarkable electrocatalytic activity for the oxygen evolution reaction (OER) in an alkaline solution with an overpotential of 214 mV at 10 mA/cm(2), a high stability for over 60 h, a low Tafel slope of 36.2 mV dec(-1), and a capability of delivering a high current density of 300 mA/cm(2) at an overpotential of 368 mV. In contrast to photodeposition, electrodeposition, and hydrothermal methods for the formation/integration of (oxy)hydroxides, this facile solution strategy for designing an attractive and efficient structure with a highly active metal (oxy)hydroxide and highly conducting NGF provides a pathway to develop other earth-abundant electrocatalysts for a multitude of energy-conversion-device applications.