Innovative synthesis of porous nickel whiskers for improved oxygen evolution reaction performance
摘要
This study investigates the formation and electrochemical properties of Ni whiskers synthesized on a Ni substrate through heat treatment in an Al-rich environment, followed by leaching in potassium hydroxide (KOH). Scanning electron microscopy (SEM) revealed distinct layers (D1 and D2) formed during heat treatment, consisting of Ni₂Al₃ and Al₃Ni phases, respectively. Over time, Al₃Ni whiskers, oriented and embedded in an Al matrix, formed on the D2 layer. Leaching of Al from these whiskers revealed nanocrystalline Ni whiskers. The study showed that both Al mass and heat treatment time significantly affected the Electrochemical Active Surface Area (EASA). Results indicated that the Ni plate had an EASA of 3 mC cm⁻2, and adding Al linearly increased the EASA to 7100 mC cm⁻2 for 350 mg Al. Longer heat treatment times, from 1 to 10 min, resulted in coarser whiskers and a lower EASA, decreasing from 7125 mC cm⁻2 to 3800 mC cm⁻2. The Ni whiskers demonstrated promising oxygen evolution reaction (OER) activity, with lower overpotentials corresponding to increased EASA. The best sample required an overpotential of 240 mV at 10 mA cm⁻2 and 350 mV at 500 mA cm⁻2. Additionally, this sample showed no degradation at 500 mA cm⁻2 for 6 days (144 h).
Graphical abstract