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

Abstract

The development of efficient, affordable, and earth-abundant bifunctional electrocatalysts is vital for the water-splitting reaction. In this article, we have fabricated NiCo2Se4 and Fe-doped NiCo2Se4 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 Fe0.2NiCo1.8Se4 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/cm2 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/cm2 current density with 24 h of stability. The Fe0.2NiCo1.8Se4 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 Fe0.2NiCo1.8Se4. The doping with Fe in NiCo2Se4 enhances the active sites and increases its electrocatalytic performance. The SCN– poisoning effect on metal ions in Fe0.2NiCo1.8Se4 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 NiCo2Se4 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 NiCo2Se4 nanorod array on the surface of carbon cloth, which is highly active and stable for water splitting in an alkaline medium.