Electrochemically-deposited NiAl-layered double hydroxide/Ni electrocatalysts for enhanced magnetic water oxidation

Abstract

The water oxidation is a promising method for generating the renewable energy. However, the high catalytic performance using stable electrocatalysts in alkali solutions remains limited. In this work, we herein report a facile method of deposition of NiAl-LDH electrocatalyst that addresses the above challenge under a magnetic field. Water oxidation behavior of the new electrodeposited nickel‑aluminum layered double hydroxides (NiAl-LDH) on Ni electroplated on the Cu substrate and their remarkable improvements in electrocatalytic activity under the external magnetic fields in alkali solutions were studied. Ni films were first electroplated on the Cu substrate using the direct current (DC) method. NiAl-LDH was coated on the Ni/Cu substrates using the electrochemical deposition method, and their water oxidation performance was investigated in the KOH aqueous solution (0.1 mol⋅L⁻¹) at 25 °C in the absence and presence of magnetic field. It was found that the oxygen evolution reaction (OER) over NiAl-LDH/Ni/Cu was improved when water oxidation was conducted under a magnetic field (μ_oH_┴ = 0.2 T) by decreasing the onset potential, Tafel slope, and overpotential or by increasing the current density (about 54 mA⋅cm⁻²). The effects were even more pronounced when the magnetic field was applied perpendicular to the electrode plane, reaching the OER overpotential of about 310 mV and the Tafel slop of about 142 mV⋅dec⁻¹. We interpreted the effect of magnetic water electrolysis by the ordinary magnetohydrodynamics (MHD) which enhanced the mass transport, increased the limiting current density, and removed the blocking oxygen gas bubbles accumulated on the electrode surface. The present investigation provides a low-cost electrocatalyst system for efficient electrochemical water oxidation.