Ni and Co Catalysts on Interactive Oxide Support for Anion Exchange Membrane Electrolysis Cell (AEMEC)

Abstract

The work presents novel composite catalytic materials—Ni and Co deposited on Magneli phase titania—and describes their complex characterization and integration into membrane electrode assemblies to produce hydrogen by electrochemical water splitting in cells with anion exchange membranes (AEMEC). Chemical composition, surface structure, and morphology were characterized by XRD and SEM analysis. The activity in the evolution of the partial electrode reactions of hydrogen (HER) and oxygen (OER) was assessed in an aqueous alkaline electrolyte (25 wt.% KOH) using linear sweep voltammetry. The interactive role of the support was investigated and discussed. Among the tested samples, the sample with 30 wt.% Co (Co30/MPT) demonstrated superior performance in the OER. The reaction started at 1.65 V, and at 1.8 V, the current density reached 75 mA cm−2. The HER is most efficient on the sample containing 40 wt.% Ni (Ni40/MPT), where the current density reaches 95 mA at a potential of −0.5 V. The change in catalytic efficiency compared to that of the unsupported Ni and Co is due to synergism resulting from electronic interactions between the transition metal having a hyper-d-electron character and hypo-d-electron support. The pre-selected catalysts were integrated in membrane electrode assembly (MEA) using commercial and laboratory-prepared anion-conductive membranes and tested in a custom-made AEMEC. The performance was compared to that of MEA with a commercial carbon-supported Pt catalyst. It was found that the MEA with newly prepared catalysts demonstrated better performance in long-term operation (50 mA cm−2 at 1.8 V in a 60 h durability test), which, combined with the higher cost efficiency, gave credence to considering this combination of materials as promising for AEMEC applications.