Synthesis and Catalyti~ Activity of Transition Metal Layered Double Hydroxides for OER in Alkaline Medium

Abstract

Electrochemical water splitting has been empirically proven to be a potential technology for hydrogen generation. Hydrogen is a promising candidate in the context of energy conversion and storage application. The oxygen evolution reaction (OER) which demands a large overpotential, stands out as the most crucial process among the various stages involved in water electrolysis. Addressing this challenge primarily involves developing OER electrocatalysts that are efficient, long-lasting, environmentally friendly, and cost-effective. The objective of present research work was to fabricate transition metal based layered double hydroxides (TM-LDHs), and their composites with rOO (TM LDHlrOO), to study their OER performance. Different TM-LDH materials (NiFe-LDH, NiCo-LDH, CoFe-LDH, NiFe-LDH/rOO, NiCo-LDHIrOO and CoFe-LDH/rOO) were successfully synthesized by hydrothermal method and confirmed by XRD and FTIR analyses. The OER activity of synthesized electrocatalysts was systematically evaluated in an alkaline medium by employing linear sweep voltarnrnetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques using glassy carbon (OC) as substrate. The CV scans displayed the characteristic redox behavior related to each modified electrode. The OER performance of all synthesized electro catalysts was compared in tenns of overpotential at 10 rnA cm-2 and the Tafel slope, which declines in the order NiFe-LDHIrOO (260 mV, 46.4 mV dec-I) > NiFe-LDH (270 mV, 51.5 mV dec-I) forNi-Fe combination, CoFe-LDH/rOO (310 mV, 53.4 mV dec-I) > CoFe-LDH (330 mY, 80.6 mV dec-I) for Co-Fe combination ofLDH and NiCo-LDH/rOO (320 mV, 77 mV dec I) > NiCo-LDH (390 mV, 77 mV dec-I) for Ni-Co combination of LDH. Among all the synthesized electrocatalysts, NiFe-LDH/rOO exhibited the highest OER activity with an overpotential of 260 m V.