Bimetallic layered-double hydroxides anchored on reduced graphene oxide as a bifunctional electrocatalyst for electrochemical water splitting

Developing efficient electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is essential for advancing a sustainable energy future. In this study, bimetallic NiMo-LDH nanoflakes were successfully integrated onto reduced graphene oxide using a straightforward hydrothermal method. The composite material was characterized by FTIR, XRD, SEM, EDS, and XPS. Electrochemical evaluations highlighted the impact of rGO content, revealing that the NiMo-LDH with 7% rGO exhibited superior performance in OER, requiring only 230 mV overpotential and a Tafel slope of 60 mV dec-1 at a current density of 10 mA cm-2 in 1.0 M KOH. This enhanced performance is attributed to improved charge separation and transfer at the electrocatalyst/electrolyte interfaces, driven by the synergistic effects of rGO and NiMo-LDH. Furthermore, the composite electrocatalyst showcased bifunctional capabilities, with promising HER performance characterized by favorable overpotential and Tafel slope in 0.5 M H2SO4. Long-term stability was confirmed through chronoamperometry, while electrochemical impedance spectroscopy revealed efficient charge transport across the modified glassy carbon electrode represented as NiMo-LDH@rGO/GCE. Additionally, the synthesized catalyst demonstrated good recoverability, exhibiting appealing onset and overpotentials.