CoNiFe anodic catalysts prepared by magnetron sputtering deposition for anion exchange membrane water electrolysis

The development of efficient catalysts for water electrolysis still remains a challenge. In this work, we investigate the effect of the addition of cobalt to the well-known NiFe anode catalysts on the oxygen evolution reaction (OER). Trimetallic CoNiFe catalysts-based electrodes with a fixed nickel/iron ratio of 90/10 and distinct cobalt contents were prepared by magnetron sputtering at oblique angle deposition (MS-OAD). The best catalytic performance was obtained for catalysts with cobalt contents ranging from 2.3 to 7.4 at.%, which presented state-of-the-art values of overpotential (231 mV at 10 mA cm −2 ) and Tafel slope (33.9 mV·dec −1 ). A thorough physicochemical and electrochemical characterization revealed that cobalt contributes to increasing electrical conductivity, the electrochemically active surface area and the concentration of catalytically active species. The formation of layered double hydroxides has also been identified as an additional factor contributing to this enhancement of the activity. Bimetallic NiFe and trimetallic CoNiFe catalysts were then proved in AEMWE cells. It is found that catalyst loadings as low as ∼0.9 mg cm −2 with 7.4 at. % of cobalt in the NiFe matrix led to a significant improvement in electrochemical activity (mass activity 13.9 A g −1 ) and stability performance.