Enhanced Oxygen Evolution during Water Electrolysis at De-Alloyed Nickel Thin Film Electrodes

Abstract

Hydrogen as an energy carrier has tremendous potential to overcome global warming issues. In this respect, production of hydrogen by water electrolysis has already been intensively studied, but its efficiency, especially in terms of the oxygen evolution reaction (OER), still needs to be improved. The objective of this work is to study the possibility of reducing the OER overpotential by de-alloying Ni thin film electrodes in order to favor bubble detachment. Ni(Al) alloys were first deposited by magnetron co-sputtering, and then chemically leached in a concentrated hydroxide solution with the aim of dissolving out the aluminum. We report X-ray diffraction analysis, scanning electron microscopy, inductively coupled plasma optical emission spectroscopy and roughness measurements to characterize our (de-)alloyed electrodes. Electrochemical testing, both cyclic voltammetry and chrono-potentiometry, has then been realized in a homemade electrochemical flow cell. Results show that different electrode compositions and intermetallic phases can be obtained by varying the deposition parameters, allowing to generate different Al/Ni atomic ratio's in the as-deposited films. Moreover, our de-alloyed electrodes present significantly lower overpotentials for the OER than untreated pure Ni electrodes. In the optimal case, a drop of as much as 140 mV was obtained at 10 mA/cm².