A comparison of cathodes for zero gap alkaline water electrolysers

Abstract

Selected coatings on nickel or stainless steel micromeshes have been examined as electrocatalysts for hydrogen evolution in conditions mimicking those found in zero gap alkaline water electrolysers. Voltammetry in 4 M NaOH at a temperature of 333 K, shows that Pt, NiMo and RuO2 are the coatings of choice giving a superior performance particularly at higher current densities. NiMo and RuO2 coatings also give stable performance during a 10 day electrolysis in a laboratory, zero gap, alkaline water electrolysis cell with a hydroxide conducting membrane; when combined with a NiFe(OH)2 coated anode, a current density of 1 A cm−2 is achieved with a cell voltage of ∼2.1 V. Pt catalyses H2 evolution efficiently at short times of electrolysis but cells with a Pt cathode show an increase in cell voltage from 2.05 V to 2.23 V during the first two days of operation.