Scale-up of Co–Ni cathodes produced from spent Ni–Cd batteries for hydrogen production in an oxy-hydrogen gas cell

Abstract

Ni(II) and Co(II) ions are recovered from real leached positive electrodes of spent Ni–Cd batteries, and subsequently co-deposited on A36 carbon steel using direct and pulsed currents. The idea is to evaluate how variations in texture and composition of recycled coatings affect their catalytic activities for H2 production at microelectrolysis levels, and using an oxy-hydrogen gas (HHO) cell. The most active Ni–Co electrocatalyst in 0.1 M HClO4 or KOH towards hydrogen evolution reaction (HER) is formed using pulsed current at −50 mA cm−2, according to electrochemical measurements and gas chromatography (GC). This plating mode favors grain size refinement and pH rise during metal deposition, to prevent the formation of oxides/hydroxides with low catalytic activity arising in direct current. In the HHO cell, the most active Co–Ni coating produces 21.63 mL min−1 H2, while A36 carbon and 304 stainless steels present lower generations of 7.30 and 7.55 mL min−1, respectively.