In spite of the drastic oil price collapse in the second half of 2014 resulting in a price below 30 $/barrel in January 2016 1 , the exploration of promising renewable energy sources for the Abstract: Water splitting allows the storage of solar energy into chemical bonds (H 2 +O 2 ) and will help to implement the urgently needed replacement of limited available fossil fuels. Particularly in neutral environment electrochemically initiated water splitting suffers from low efficiency due to high overpotentials (η) caused by the anode. Electro-activation of X20CoCrWMo10-9, a Co-based tool steel resulted in a new composite material (X20CoCrWMo10-9//Co 3 O 4 ) that catalyzes the anode half-cell reaction of water electrolysis with a so far-, unequalled effectiveness. The current density achieved with this new anode in pH 7 corrected 0.1 M phosphate buffer is over a wide range of η around 10 times higher compared to recently developed, up-to-date electrocatalysts and represents the benchmark performance advanced catalysts show in regimes that support water splitting significantly better than pH 7 medium. X20CoCrWMo10-9//Co 3 O 4 exhibited electrocatalyticproperties not only at pH 7, but also at pH 13, which is much superior to the ones of IrO 2 -RuO 2 , single-phase Co 3 O 4 -or Fe/Ni-based catalysts. Both XPS and FT-IR experiments unmasked Co 3 O 4 as the dominating compound on the surface of the X20CoCrWMo10-9//Co 3 O 4 composite. Upon a comprehensive dual beam FIB-SEM (focused ion beam-scanning electron microscopy) study we could show that the new composite does not exhibit a classical substrate-layer structure due to the intrinsic formation of the Co-enriched outer zone. This structural particularity is basically responsible for the outstanding electrocatalytic OER performance.2 future is one of the significant challenges for scientists and engineers concerned with energy issues research. Splitting of water into hydrogen and oxygen by exploiting solar energy transforms water to an inexhaustible and environmental friendly fuel source 2,3,4,5,6,7,8,9 .Electrocatalytically initiated hydrogen-and oxygen formation from water is considered an important realization of this solar to fuel conversion route 10,11,12 but is typically hampered by the high overpotentials oxygen evolution on the anode side goes with 13,14 . This is particularly true when the electrochemical cleavage of more or less untreated water is intended-; hence, when the splitting procedure is carried out at neutral pH value. 17,18,19,20,21,22,23,24 . Scheme 1 gives some idea of the position of current heterogeneous catalysts in terms of their efficiency regarding OER in neutral regime. The significant improvement of the voltage-current behavior can be taken from both-, the non-steady state ( Figure 1a) as well as the steady state polarization (Figure 1b) experiments.
Results
OER properties in neutral mediumThe CV of sample Co-300 shows along the entire curve substantially stronger current to voltage ratio than the CV of sample Co and reached, at the upper...
