NiFe Oxalate Nanomesh Array with Homogenous Doping of Fe for Electrocatalytic Water Oxidation

NiFe-based materials have shown impressive electrocatalytic activity for the oxygen evolution reaction (OER). The mutual effect between proximate Ni and Fe atoms is essential in regulating the electronic structure of the active site to boost the OER kinetics. Detailed studies confirm that the separated monometal phases in NiFe-based materials are detrimental to OER. Thus, the high-level blending of Ni and Fe in NiFe-based OER electrocatalysts is critical. Herein, an NiFe oxalate nanomesh array based on solid solutions between nickel (II) oxalate and iron (II) oxalate is prepared through a facile surfactant-free approach in the presence of the reductive oxalate anions. The integrated electrode can efficiently catalyze water oxidation to reach a current density of 50 mA cm^-2 with a small overpotential of 203 mV in a 1.0 m KOH aqueous solution. The high efficiency can be attributed to the atomic level mix of Ni and Fe in the solid solutions and the hierarchical porous structure of the nanomesh array. These two aspects bring about fast kinetics, efficient mass diffusion, and quick charge transfer, which are the three major positive factors for a high-performance heterogenous electrocatalyst.