NiFe₂O₄ in MoSe₂ Exhibits Bifunctional Water Oxidation and Oxygen Reduction (OER and ORR) Catalytic Reactions for Energy Applications

Highly active bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts made of nickel ferrite (NiFe₂O₄) supported on molybdenum diselenide (MoSe₂) nanosheets have been rigorously studied in our present work. The OER activity evaluation was conducted in an alkaline solution for all catalysts. The MoSe₂@NiFe₂O₄ (1:1) catalyst, which had shown superior activity compared to other catalysts, has an onset potential of 1.50 V vs reversible hydrogen electrode (RHE), similar to the state-of-the-art commercial IrO₂. The ORR activity of the MoSe₂@NiFe₂O₄ electrocatalyst exhibited an ORR onset potential of 0.83 V vs RHE. We report the MoSe₂@NiFe₂O₄ bifunctional catalyst for noticeable activity in ORR and OER, with a potential difference (ΔE) of 0.92 V. In the accelerated test, after 5000 potential cycles, the MoSe₂@NiFe₂O₄ (1:1) catalyst had about 86% retention of the ORR diffusion-limiting current density. The OER depicts a loss of around 70.6% after 2000 cycles, which is significantly lower than that of the state-of-the-art IrO₂, deactivated after 2000 cycles. Harnessing the excellent bifunctionality of our catalyst, we tested the catalyst in the Zn-air battery, which depicts 300 cycles. The Zn-air battery long-term cycling test was performed at 20 mA cm^-2 to assess the stability of the hybrid catalyst (30 min cycle^-1), which exhibits a discharge voltage of 1.13 V and a charging voltage of 2.20 V. Considering the excellent bifunctional activity, the MoSe₂@NiFe₂O₄ heterostructured composite is an exceptional candidate for energy storage applications.