Iron substitution enabled lattice oxygen oxidation and cation leaching for promoting surface reconstruction in electrocatalytic oxygen evolution.

A simple Fe element substitution strategy is developed to regulate the surface reconstruction of spinel oxide NiCr 2 O 4 by accelerating the consumption of lattice oxygen and the leaching of soluble Cr cations. Consequently, the electrochemically activated Fe-doped NiCr 2 O 4 (Act-Fe-NCO) exhibits outstanding OER performance. [Display omitted] The low-cost transition metal oxides have drawn widespread interest as alternatives to noble metal-based electrocatalysts for oxygen evolution reaction (OER). Transition metal oxides usually undergo surface reconstruction during electrochemical reaction to form the actual active species. However, in-depth understanding and regulating of the surface reconstruction of active phases for oxides in OER remains an onerous challenge. Herein, we report a simple Fe element substitution strategy to facilitate the surface reconstruction of spinel oxide NiCr 2 O 4 to generate active (oxy)hydroxides. The activated Fe-doped NiCr 2 O 4 (Act-Fe-NCO) exhibits a lower OER overpotential of 259 mV at 10 mA cm−2 than activated NiCr 2 O 4 (Act-NCO, 428 mV), and shows excellent stability for 120 h. The electrochemically activated CV measurement and nanostructure characterizations reveal that Fe substitution could promote the consumption of lattice oxygen during electrochemical activation to induce the leaching of soluble Cr cations, thereby facilitating the reconstruction of remaining Ni cations on the surface into (oxy)hydroxide active species. Moreover, theoretical calculations further demonstrate that the O 2p band center of NiCr 2 O 4 moves towards the Fermi level due to Fe substitution, thus promoting lattice oxygen oxidation and providing greater structural flexibility for surface reconstruction. This work shows a promising way to regulate the surface reconstruction kinetics and OER electrocatalytic activity of transition metal oxides. [ABSTRACT FROM AUTHOR]