AB5-catalyzed hydrogen evolution cathodes

The AB5 metal compounds are highly efficient hydrogen evolution electrocatalysts in alkaline electrolyte. Three types of AB5-catalyzed cathode structures were made, using the hydride-forming AB5 compounds in particulate form. Plastic-bonded cathodes containing >90 w/o AB5 (finished-weight basis) were the most efficient, giving hydrogen evolution overpotentials (νH2) of about 0.05 V at 200 mA cm−2. However, they tended to swell and shed material during electrolysis. Pressed, sintered cathodes containing 40–70 w/o catalyst in a nickel binder gave νH2 ∼ 0.08 V; catalyst retention was excellent. Porous, sintered cathode coatings were made with 30–70 w/o AB5 catalyst loadings. Their overpotentials were similar to those of the pressed, sintered cathodes. However, at catalyst loadings below about 40 w/o, high overpotentials characteristic of the nickel binder were observed. The structural and electrochemical properties of the three AB5-catalyzed cathodes are discussed.