Self-reconstruction of a MOF-derived chromium-doped nickel disulfide in electrocatalytic water oxidation

Developing high-performance electrocatalysts with in-depth understanding in reaction mechanisms require not only delicate synthetic technologies, but also advanced analytical methodologies. While catalytic performance can be boosted through the construction of porous nanostructures for enlarged surface area, mechanism studies generally depend on sophisticated in-situ characterization techniques. In the present work, we report a hierarchically porous nanostructure of chromium-doped nickel disulfide as an active electrocatalyst for water oxidation, which exhibits a low overpotential of 207 mV to drive 10 mA cm−2 in alkaline medium. The surface evolution at different reaction stages is revealed utilizing specifically designed ex-situ characterization approaches. An irreversible self-reconstruction from Cr-doped NiS2 to Cr, S co-doped Ni(OH)2 followed by a reversible transformation into NiOOH is observed in cyclic voltammetry processes, indicating that NiS2 plays a key role as pre-catalyst to generate highly active sites for electrocatalytic water oxidation.