Electrodeposition at Highly Negative Potentials of an Iron-Cobalt Oxide Catalyst for Use in Electrochemical Water Splitting

Abstract

Earth-abundant transition metal-based catalysts have been extensively investigated for their applicability in water electrolysers to enable overall water splitting to produce clean hydrogen and oxygen. In this study a Fe-Co based catalyst is electrodeposited in 30 seconds under vigorous hydrogen evolution conditions to produce a high surface area material that is active for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). This catalyst can achieve high current densities of 600 mAcm^-2 at an applied potential of 1.6 V (vs RHE) in 1 M NaOH with a Tafel slope value of 48 mV dec^-1 for the OER. In addition, the HER can be facilitated at current densities as high as 400 mA cm^-2 due to the large surface area of the material. The materials were found to be predominantly amorphous but did contain crystalline regions of CoFe₂ O₄ which became more evident after the OER indicating interesting compositional and structural changes that occur to the catalyst after an electrocatalytic reaction. This rapid method of creating a bimetallic oxide electrode for both the HER and OER could possibly be adopted to other bimetallic oxide systems suitable for electrochemical water splitting.

Keywords: electrocatalysis; electrodeposition; negative potential; porous cobalt-iron; water splitting.