The enhanced electrocatalytic activity of Cr-doped NiC2O4 for water splitting via surface reconstruction

Electrolysis of water to produce hydrogen can alleviate the problem of global energy shortage, and seeking efficient water splitting electrocatalysts is the promising direction. In this work, Cr-doped nickel oxalate (Cr-NiC₂O₄/NF) was synthesized on nickel foam (NF) by a one-step hydrothermal method and used as an alkaline electrolytic water catalyst. The electrocatalytic activity of NiC₂O₄ is significantly improved by Cr doping. For the oxygen evolution reaction (OER), the overpotential is 324 mV at 100 mA cm^-2, and for the hydrogen evolution reaction (HER), the overpotential is 191 mV at 10 mA cm^-2. When Cr-NiC₂O₄/NF is used as anode and cathode in water splitting, only voltage of 1.58 V is required at current density of 10 mA cm^-2. Furthermore, the mechanism of enhanced catalytic activity via surface reconstruction during the OER and HER was systematically studied. The pre-catalyst Cr-NiC₂O₄ was restructured into hydroxides and hydroxyl oxides for OER, and some Cr-NiC₂O₄ was converted into hydroxides for HER. Consequently, this investigation provides a new method to improve the electrocatalytic performance of metal oxalates and a theoretical guidance for surface reconstruction.