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

Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents

“…Furthermore, it is obvious that the RuO2 coating also contains Ni in some form as the oxidation peak for Ni 2+ /Ni 3+ at about + 0.30 V vs. SCE is observed in the cyclic voltammetry of all three samples and, in addition, the Ni 0 /Ni 2+ peak at -0.85 V in the first scan of the HER (2 h) sample [6,26,27]. Nickel content in RuO2 coatings applied on Ni substrates has been confirmed with XPS [18].…”

“…A large oxidation peak appears at about -1.05 V vs. SCE caused by re-oxidation of hydrogen gas trapped inside the nanoporous coating structure [6,23]. More important is, however, the oxidation peak at about +0.15 V vs. SCE indicating oxidation of Ru 4+ to Ru 6+ , which suggests formation of ruthenate ions, RuO4 2- [6,24,25]. The RuO4 2-formation is also observed in the first cycle of the reference sample, which is a consequence of that the cyclic voltammetry starts on the HER side.…”

“…Although several authors have reported loss of catalyst material as an effect of reverse currents [3][4][5][6], the long-term stability of RuO2-based coatings has not been well studied. In the previous studies reverse current was introduced by polarity inversion, i.e.…”

Ni-MoO2 cathodes for hydrogen evolution in alkaline solutions. Effect of the conditions of their electrodeposition

“…Recently, particular attention has been given to the replacement of expensive Ni + RuO 2 [14] composite coating with coatings obtained by the electrodeposition of Ni with molybdenum oxide species [16][17][18][19][20]. It was shown that Ni-MoO 3 [16,20] composite coatings, electrodeposited from a suspension containing different concentrations of MoO 3 particles in a Watt's type bath, possess good catalytic activity, but their properties during the "service life" test were not good enough for application in industrial electrolysis [18].…”

“…Hence, for industrial application, advanced electrocatalytic materials for HER are of great importance to increase energy efficiency. Since porous Ni (Raney Ni) electrodes showed extensive deactivation during electrolysis, several approaches to design and produce new electrocatalytic cathode materials have been presented in the past [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. One of these approaches is based on the Brewer intermetallic bonding theory, which predicts a synergetic activation effect whenever metals of the left half of the d-series are alloyed with metals of the right half of the d-series [4][5][6][7][8][9][10].…”