Oxygen Evolution Reaction on Ni-based Two-dimensional (2D) Titanate Nanosheets: Investigation on Effect of Fe Co-doping and Fe Incorporation from Electrolyte on the Activity

In this paper, Ni-based titanate nanosheets are used as a model system to reveal how incorporation of Fe affects their catalytic ability for the oxygen evolution reaction (OER). The Fe incorporation effects are studied without structural and morphological changes due to the rigid framework of TiO2 based nanosheets. Transition metal doped titanate nanosheets are prepared by cation-assisted exfoliation of protonated layered potassium titanate. Fe incorporation within the lattice of Ni doped titanate nanosheets by co-doping stabilizes nickel ions in lower oxidation state by charge transfer effect, caused increased OER activity at Ni sites by the electronic interaction. In contrast, incorporation of Fe from the electrolyte, highly-active Fe sites at edges or corners of Ni doped titanate nanosheets are formed by electrochemical cycling in Fe-containing electrolyte rather than electronic effects on Ni. Through this work, Fe incorporation effects are experimentally revealed without crystal structural or morphological changes, and a method to produce a highly active and stable OER catalyst is provided.