Interface-driven electrocatalytic activity of NiFe-LDH on MnO2-modified SWCNT hierarchical nanostructures for overall water splitting

Developing cost-effective bifunctional electrocatalysts is important for sustainable and clean energy production. Herein, a hierarchical NiFe layered double hydroxide integrated with MnO 2 nanorods and single-walled carbon nanotubes (NiFe-LDH@MnO 2 /SWCNT) was synthesized to enhance bifunctional catalytic activity toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The synergistic coupling between Ni and Fe promotes high-valent Ni active sites that facilitate OH⁻ adsorption and accelerate OER kinetics, whereas synergistic adsorption of hydrogen and hydroxyl intermediates facilitates improved HER performance. The incorporation of multivalent MnO 2 introduces redox-active centers that enhance electron transfer and intermediate formation, whereas the conductive SWCNT framework provides rapid charge transport and increased electrochemically active surface area. Among the synthesized catalysts, NiFe-LDH@3-MnO 2 /SWCNT exhibits superior electrocatalytic performance, with low overpotentials of 206 mV for OER and 198 mV for HER at 10 mA cm -2 with a small OER Tafel slope of 33 mV dec -1 . Comparative analyses demonstrate that the catalyst outperforms several previously reported NiFe-LDH and MnO 2 -based systems, exhibiting faster reaction kinetics and improved efficiency. The enhanced activity achieved from hierarchical architecture, improved electrolyte diffusion, and strong interfacial electronic coupling. These results reveal that NiFe-LDH@MnO 2 /SWCNT is a promising electrocatalyst for efficient overall water splitting.