Fe-Doped NiCo₂Se₄ Nanorod Arrays as Electrocatalysts for Overall Electrochemical Water Splitting

The development of efficient, affordable, and earth-abundant bifunctional electrocatalysts is vital for the water-splitting reaction. In this article, we have fabricated NiCo 2 Se 4 and Fe-doped NiCo 2 Se 4 through a simple hydrothermal route on the surface of carbon cloth with nanorod morphology. The developed electrocatalyst was thoroughly investigated by various techniques like PXRD, XPS, FESEM, ICP-AES, and TEM analysis. The optimized Fe 0.2 NiCo 1.8 Se 4 has worked finest for hydrogen and oxygen evolution in an alkaline medium; it entails a potential of 148 mV and 1.656 V vs RHE to obtain 50 and 100 mA/cm 2 current densities for HER and OER, respectively. The Tafel slope values for HER and OER are 85.7 and 56.3 mV/dec, respectively. This catalyst is stable under an alkaline medium for 48 h. The best HER and OER activity recommends the catalyst as a bifunctional in an alkaline medium, and the developed cell consisting of a doped sample requires 1.51 V to generate a 10 mA/cm 2 current density with 24 h of stability. The Fe 0.2 NiCo 1.8 Se 4 catalyst has a good Faradaic efficiency of 89.9% for overall water splitting. The nanorod morphology has a specific role in enhancing the electron transportation and conductivity of Fe 0.2 NiCo 1.8 Se 4 . The doping with Fe in NiCo 2 Se 4 enhances the active sites and increases its electrocatalytic performance. The SCN – poisoning effect on metal ions in Fe 0.2 NiCo 1.8 Se 4 suggests that Fe, Co, and Ni metals have a prominent impact on the overall electrocatalytic activity. Additionally, DFT investigation indicates that after Fe doping in a NiCo 2 Se 4 zero band gap, minimum Gibbs free energy, maximum hydrogen, and oxygen coverage calculations are accountable for the higher conductivity of the system. This research provides a simple approach for synthesizing a Fe-doped ternary NiCo 2 Se 4 nanorod array on the surface of carbon cloth, which is highly active and stable for water splitting in an alkaline medium.