Spontaneous corrosion on the surface: Ni-regulated oxalates grown in situ on stainless steel for efficient oxygen evolution

Abstract

Bimetallic NiFe-based materials are widely certified for their high performance in the oxygen evolution reaction (OER). In this work, a hydrothermal method was used to activate stainless steel (SS) with oxalic acid. The SS was used as the Fe source and carrier, and the in situ-grown NiFe oxalate microcrystals were synthesized by introducing a certain percentage of nickel to modulate the crystallographic appearance. In the crystal, the doped Ni couples with the surrounding Fe, prompting coordination defects in the lattice and generating more active vacancies. Meanwhile, the lattice deformation hinders the further stacking of the crystals, and the morphology of oxalates is regulated. This phenomenon is beneficial to optimize the intermediate adsorption step. In addition, the oxalate anions with strong complexation ability prevent the dissolution of the active substances during the catalytic process. Hence, NIO-SS electrode require only 315 mV and 391 mV of overpotential to achieve current densities of 50 and 100 mA·cm−2. At the same time, the stability of 100 h is maintained. This work presents a novel idea to improve the OER performance of stainless steel by spontaneous corrosion and Ni-regulated of the generated oxalates, promising to be used in actual production.