The advancement of affordable bifunctional electrocatalysts is crucial for improving both the hydrogen evolution reaction (HER) and the urea electro-oxidation reaction (UOR). In this work, the dynamic hydrogen bubble template (DHBT) technique was utilized to create a three-dimensional (3D) Ni3S2 substrate, effectively enhancing the active surface area. Following this, Co-Mn-Se nanosheets were grown on the 3D microporous Ni3S2 surface via a cyclic voltammetry (CV) method. To verify the successful synthesis of Co-Mn-Se nanosheets on the 3D microporous Ni3S2 substrate, various characterization techniques were employed. These included transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR), all of which provided conclusive evidence of the nanosheet formation and the uniformity of the coating on the substrate. Electrochemical results demonstrated that the 3cycles-Co-Mn-Se@Ni3S2 sample exhibited the best performance, requiring overpotentials of 81, 106, and 180 mV at current densities of 10, 20, and 100 mA cm-2 for HER, respectively. For UOR, overpotentials of 301, 393, and 481 mV were required at current densities of 10, 100, and 200 mA cm-2. In urea-assisted water splitting, this sample achieved a current density of 100 mA cm-2 at 1.716 V, providing a 199 mV reduction in potential compared to traditional methods (methods not using urea). This work highlights the potential of Co-Mn-Se as a high-performance electrocatalyst and demonstrates the effectiveness of the DHBT method in enhancing catalytic activity on 3D nanostructured substrates.

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