Electron-modulated amorphous RH(OH)₃-decorated NiMn-LDH: A superior bifunctional electrocatalyst for...

Developing efficient bifunctional (oxygen evolution reaction/hydrogen evolution reaction, OER/HER) catalysts for alkaline water electrolysis (AWE) under industrial current densities remains a critical challenge, primarily due to sluggish reaction kinetics, high overpotentials, and catalyst degradation. Herein, we fabricate an amorphous rhodium hydroxide (Rh(OH)₃)-decorated nickel‑manganese layered double hydroxide (a-Rh(OH)₃/NiMn-LDH) heterostructured catalyst via hydrothermal synthesis and infrared photoreduction, which serves as a superior bifunctional electrocatalyst for industrial AWE. The core enhancement mechanism relies on Ni-O-Rh interfacial bridges: X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) characterizations, and density functional theory (DFT) calculations confirm that these bonds function as efficient electron transfer channels, which induce charge redistribution between nickel (Ni, in NiMn-LDH) and rhodium (Rh, in a-Rh(OH)₃), elevating the Ni oxidation state (facilitating the Ni²⁺ → Ni³⁺ transition for OER activation), optimizing the Ni d-band center, and modulating the adsorption of *OH, *O, *OOH, and *H intermediates to accelerate catalytic kinetics. Notably, in 1.0 M KOH electrolyte, the catalyst achieves ultralow overpotentials (378 mV for OER, 245 mV for HER) at a current density of 500 mA cm^-2. The AWE device using this catalyst as both the cathode (for HER) and anode (for OER) delivers a current density of 500 mA cm^-2 at a cell voltage of 1.81 V and maintains stable operation for over 1000 h (with only 51 mV voltage decay), outperforming the commercial ruthenium dioxide||platinum on carbon (RuO₂||Pt/C) catalyst couple and most reported nickel/cobalt (Ni/Co)-based bifunctional catalysts. This work highlights the significance of Ni-O-Rh interfacial engineering for LDH-based catalysts, providing a promising strategy for designing advanced bifunctional catalysts toward industrial AWE applications.