Non-noble metal composite cathodes for hydrogen evolution. Part II: The Ni–MoO2 coatings electrodeposited from nickel chloride–ammonium chloride bath containing MoO2 powder particles

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

“…1b). A homemade power supply, with a ripple smaller than 1 %, was used to apply the required current/voltage [16,17].…”

“…Electrodeposition of Ni-MoO 2 composite coating started after 24 h of electrolyte aging (following experience from our previous work [17]). The electrolyte flow rates were set at two values, 10 and 20 dm 3 min -1 , while the air flow rates were 1, 5, 10, and 20 dm 3 min -1…”

“…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].…”

“…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].…”

“…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]. On the other hand, Ni-MoO 2 composite coatings electrodeposited from a suspension containing 3 g dm -3 MoO 2 particles in a solution of 0.2 M NiCl 2 + 2 M NH 4 Cl were found to be a promising replacement [17,18] for commercial Ni + RuO 2 coating obtained by a similar electrodeposition procedure. Taking into account that the commercial Ni + RuO 2 cathodes were electrodeposited by incorporation of RuO 2 particles in an Ni matrix, in this work an attempt was made to produce NiMoO 2 composite coatings from a suspension of MoO 2 particles in a Watt's type bath under different conditions (different concentrations of MoO 2 particles, different current densities, and different hydrodynamic conditions) and to compare their polarization characteristics for HER in 1 M NaOH with that for the commercial Ni + RuO 2 coating.…”