X20CoCrWMo10-9//Co3O4: a Metal-Ceramic Composite with Unique Efficiency Values for Water-Splitting in Neutral Regime

TL;DR

This paper reports a novel Co-based composite catalyst with exceptional efficiency for water splitting at neutral pH, outperforming existing catalysts and revealing unique structural features responsible for its high activity.

Contribution

Introduction of a new X20CoCrWMo10-9//Co3O4 composite catalyst with superior water electrolysis performance, especially at neutral pH, due to its unique surface structure and composition.

Findings

Achieves over ten times higher current density than recent catalysts at pH 7.

Exhibits high electrocatalytic activity at both pH 7 and pH 13.

Surface analysis shows Co3O4 as the dominant compound with a unique outer zone structure.

Abstract

Water splitting allows the storage of solar energy into chemical bonds (H2+O2) 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 caused by the anode. Electro-activation of X20CoCrWMo10-9, a Co-based tool steel resulted in a new composite material (X20CoCrWMo10-9//Co3O4) 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 overpotentials 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//Co3O4 exhibited electrocatalytic properties not only at pH 7, but also at pH 13, which is much superior to the ones of IrO2-RuO2, single-phase Co3O4- or Fe/Ni- based catalysts. Both XPS and FT-IR experiments unmasked Co3O4 as the dominating compound on the surface of the X20CoCrWMo10-9//Co3O4 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.