Service life test of non-noble metal composite cathodes for hydrogen evolution in sodium hydroxide solution

Abstract

In this work polarization characteristics and "service life" test of the non-noble metal composite coatings Ni-MoOx and Ni-MoO2 for hydrogen evolution reaction (HER) in 32 wt.% NaOH at 90 degrees C were investigated and compared with that recorded for De Nora's commercial Ni + RuO2 cathode coating (DN). It was shown that under conditions of industrial application in the "zero-gap" membrane cells the lowest over-voltage for HER has been recorded for the Ni-MoO2 coating. At the same time the "service life" test was performed on all three electrodes in the same solution. This test was based on monitoring the current density response before and after repetitive cycling of these electrodes with 50 mV s(-1) in the potential range from hydrogen (-1.25 V vs. SCE) to oxygen (0.50 V vs. SCE) evolution. It was shown that the activity for all electrodes at the end of a "service life" test dropped to approximately 54% of the initial value, being comparable with the results obtained for Pt-based cathodes. The SEM-EDS analysis of the electrodes after the "service life" test showed that the Ni-MoO2 is much more stable than the Ni-MoOx composite coating and could be promising replacement for the commercial cathode.