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