Designing of CQDs-decorated NiMn₂S₄ Nanosheets as Oxygen Evolution Reaction Electrocatalysts for Water Electrolysis

This study explores a morphology-controlled synthesis strategy for an innovative hybrid nanostructure composed of carbon quantum dots (CQDs) integrated with NiMn₂S₄ nanosheets, designed to enhance the oxygen evolution reaction (OER) performance. Uniform, ultrathin, and regular discrete nanosheet arrays were grown on nickel foam via hydrothermal synthesis followed by calcination at 400 °C. The low thickness of the nanosheets increases the number of active sites for the OER. Moreover, the interconnected nanosheet framework facilitates the transport of electrolyte ions and enables efficient bubble release during OER. In addition, the intimate integration of ultrathin nanosheets with the substrate promotes efficient electron transfer and improves long-term stability. Notably, the CQDs/NiMn₂S₄ hybrid exhibits a low overpotential of 350 mV at a current density of 10 mA cm^− 2, along with excellent stability over 55 h of operation. The structure and morphology of the CQDs/NiMn₂S₄ composite were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy. This work provides an innovative strategy for enhancing the OER performance of NiMn₂S₄ through surface decoration with carbon quantum dots for water-splitting applications.

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