Electro-Oxidation of Ni42 Steel: A highly Active Bifunctional Electrocatalyst

TL;DR

This study demonstrates that anodized Ni42 steel acts as a highly active, stable bifunctional electrocatalyst for water splitting, outperforming some existing catalysts in efficiency and durability across various pH levels.

Contribution

The paper introduces a novel use of anodized Ni42 steel as a bifunctional water-splitting catalyst with superior activity and stability compared to traditional catalysts like IrO2-RuO2.

Findings

Achieved four times higher current density than recent OER catalysts.

Demonstrated high stability with no degradation under industrial conditions.

Identified gamma-NiO(OH) and FeO(OH) as active catalytic species.

Abstract

Janus type Water-Splitting Catalysts have attracted highest attention as a tool of choice for solar to fuel conversion. AISI Ni 42 steel was upon harsh anodization converted in a bifunctional electrocatalyst. Oxygen evolution reaction- (OER) and hydrogen evolution reaction (HER) are highly efficiently and steadfast catalyzed at pH 7, 13, 14, 14.6 (OER) respectively at pH 0, 1, 13, 14, 14.6 (HER). The current density taken from long-term OER measurements in pH 7 buffer solution upon the electro activated steel at 491 mV overpotential was around 4 times higher (4 mA/cm2) in comparison with recently developed OER electrocatalysts. The very strong voltage-current behavior of the catalyst shown in OER polarization experiments at both pH 7 and at pH 13 were even superior to those known for IrO2-RuO2. No degradation of the catalyst was detected even when conditions close to standard industrial operations were applied to the catalyst. A stable Ni-, Fe- oxide based passivating layer sufficiently protected the bare metal for further oxidation. Quantitative charge to oxygen- (OER) and charge to hydrogen (HER) conversion was confirmed. High resolution XPS spectra showed that most likely gamma-NiO(OH) and FeO(OH) are the catalytic active OER and NiO is the catalytic active HER species.