Enhancing oxygen evolution reaction performance of ultrasonically treated nickel electrodes in alkaline media

Abstract

This study investigates the effects of ultrasonic treatment on the oxygen evolution reaction (OER) performance of polycrystalline nickel electrodes in alkaline media. Both continuous and pulsed ultrasonic treatments were applied, with durations ranging from 15 to 60 minutes. Scanning electron microscopy revealed the formation of a porous surface structure, contributing to a 4.2-fold increase in electrochemically active surface area after 60 minutes of treatment. Linear sweep voltammetry showed a progressive enhancement in OER activity, with the exchange current density increasing from 3.2 × 10⁻⁷ A/cm² for the untreated electrode to 2.8 × 10⁻⁵A/cm² for the 60-minute treated electrode. Pulsed ultrasound treatment demonstrated superior performance compared to continuous treatment, yielding a lower Tafel slope of 55 mV/dec versus 60 mV/dec. X-ray photoelectron spectroscopy analysis indicated an increase in surface oxides and hydroxides from 18.3 % to 67.5 % after treatment. Rotating disk electrode experiments confirmed improved mass transport properties, with kinetic current densities at 500 mV overpotential increasing from 72.3 mA/cm² to 198.6 mA/cm². High-speed imaging revealed cavitation-induced phenomena during ultrasonic treatment, contributing to the formation of active sites and nanostructuring. These findings demonstrate the potential of ultrasonic treatment, particularly in pulsed mode, as an effective method for enhancing the OER performance of nickel-based electrocatalysts.