Fabrication of Alkaline Electrolyzer Using Ni@MWCNT as an Effective Electrocatalyst and Composite Anion Exchange Membrane

Abstract

Here, we report the synthesis of nickel nanoparticles thermally encapsulated in multiwalled carbon nanotubes (MWCNTs) and its utility in alkaline water splitting by combining with composite thermoset anion-exchange membrane. Ni@MWCNT displayed both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It provided 10 mA cm−2 current density at an overpotential of 300 mV for OER and 254 mV for HER on a glassy carbon electrode, respectively. Base-catalyzed N-methly-4-piperidone-formaldehyde-based prepolymer was grafted on to poly(vinyl alcohol) and cross-linked via thermal annealing followed by quaternization using methyl iodide to obtain thermoset anion exchange membrane (NMPi). Composite NMPi membranes were synthesized using additives tetraethyl orthosilicate (TEOS) and zirconium oxychloride. The water splitting performance on the fabricated membrane electrode assembly was tested and compared with commercially available Neosepta membrane. The obtained faradic efficacy of the water splitting was 94.33% for ZrO2-NMPi membrane followed by 80.23%, 77.70%, and 65.10% for SiO2NMPi, NMPi, and Neosepta membranes, respectively. The best membrane ZrO2-NMPi achieved maximum current density of ∼0.776 A cm−2 in 5 M KOH electrolyte at 80 °C and 2 V applied constant voltage. The excellent alkaline stability of MEA indicates its potential utility in hydrogen generation applications.