Electrocatalytic study of carbon dots/Nickel iron layered double hydroxide composite for oxygen evolution reaction in alkaline medium

The synthesis and strategic deployment of inexpensive, efficient, and robust catalysts for the oxygen evolution reactions (OER) has assumed importance due to their key role in energy conversion and storage. In this work, Cyamopsis tetragonoloba extract derived nitrogen doped carbon dots (NDCDs) supported NiFe layered double hydroxide stacked sheets (NiFe LDH@NDCDs) had been successfully synthesized by easy solvothermal method. Structural morphology and crystalline nature of the synthesized NiFe LDH@NDCDs were characterized by Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction spectroscopy. The performance of the synthesized NiFe LDH@NDCDs in electrocatalytic oxygen evolution reaction (OER) was estimated by linear sweep voltammetry (LSV), Tafel, Electrochemical Impedance spectroscopy (EIS), cyclic voltammetry, and chronopotentiometry measurements in 0.1 M KOH. The synthesized NiFe LDH@NDCDs demonstrated the small overpotential of 0.385 V-RHE to attain current density of 10 mA/cm(2), which was lesser than NiFe LDH (0.425 V-RHE), the state of the art (RuO2 = 0.422 V-RHE), NDCDs (0.534 V-RHE) and Bare Ni foam (0.541 V-RHE). The calculated Tafel slopes of synthesized NiFe LDH@NDCDs showed smaller value (93 mV/dec) than NiFe LDH, RuO2, and Bare Ni foam. The EIS studies exposed that the total resistance (R-1 + R-2) of NiFe LDH@NDCDs (63.85 omega/cm(2)) was lower than the total resistance of NiFe LDH (82.58 omega/cm(2)) and resistance of Bare Ni foam (123.8 omega/cm(2)), which revealed the good conductivity and electro activity of NiFe LDH@NDCDs. Moreover, the stability of the synthesized NiFe LDH@NDCDs was analyzed by chronopotentiometry for 6 h at a constant current density of 10 mA/cm(2). Thus the results of the present study established NiFe LDH@NDCDs as an efficient electrocatalyst for the OER in alkaline medium.