A Defect-Rich O−MoS2/NiFe-Layered Double Hydroxide/Multiwalled Carbon Nanotube Heterostructure for Overall Water Splitting

Abstract The development of high-performance bifunctional electrocatalysts for water splitting is vital for sustainable hydrogen evolution. Herein, an oxygen-incorporated MoS2/NiFe-layered double hydroxide (LDH)/multiwalled carbon nanotube (MWCNT) heterostructure with abundant defect sites was rationally designed and synthesized to enhance the electrocatalytic performance toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). X-ray photoelectron spectroscopy (XPS) reveals mixed-valence states and binding-energy shifts, indicating strong interfacial electronic interactions, while electron paramagnetic resonance (EPR) and Raman spectroscopy confirm the presence of defect sites and enhanced structural disorder. These features facilitate charge transfer and optimize the adsorption of reaction intermediates. As a result, the optimized catalyst delivers excellent oxygen evolution reaction (OER) activity with a low overpotential of 204 mV at 10 mA/cm2 and a small Tafel slope of 57 mV dec−1, along with excellent hydrogen evolution reaction (HER) performance requiring only 159 mV at 10 mA/cm2. Remarkably, the catalyst demonstrates exceptional durability with stable 72 h operation for both OER and HER and enables efficient overall water splitting at a low cell voltage of 1.58 V for over 100 h of continuous electrolysis. The overall performance is attributed to the synergistic effect of defect engineering and electronic modulation, making this heterostructure a promising candidate for efficient and durable water-splitting applications.