Mechanistic and DFT Insights Into Co‐Catalytic MgFe‐LDH/Hematite Interfaces for Efficient Photoelectrochemical Water Oxidation

ABSTRACT Layered double hydroxides (LDHs) are low‐cost and versatile materials, many of which are well‐established water oxidation electrocatalysts. A simple MgFe‐LDH variant, synthesized as size‐tunable nanosheets, was successfully decorated on the surface of hematite ( α ‐Fe 2 O 3 ) nanorods to structure an integrating photoanode for improved photoelectrochemical (PEC) water oxidation. Combined XPS and SEM analysis showed that MgFe‐LDH decoration does not interfere with the nanostructure of the light‐harvesting α ‐Fe 2 O 3 . However, intensified Raman bands for the decorated α ‐Fe 2 O 3 pointed to enhanced interactions between MgFe‐LDH and α ‐Fe 2 O 3 . Optimization of the surface amount for MgFe‐LDH can lead to a 340 mV cathodic shift in the onset potential at 0.1 mA cm −2 . Mott‐Schottky analysis and electrochemical impedance spectroscopy further revealed that LDH decoration enhances the photogenerated charge‐carrier separation and efficiently consumes holes accumulating at the electrode surface. Furthermore, density functional theory (DFT) calculations suggest a lower Gibbs free energy (ΔG) value of 1.35 eV for MgFe‐LDH/ α ‐Fe 2 O 3 contrasted to pristine α ‐Fe 2 O 3 (ΔG of 1.46 eV) for the rate‐determining step (RDS), further indicating that the MgFe‐LDH co‐catalyst lowers the activation energy barrier for the OER. This work offers a promising method for designing high‐efficiency and low‐cost hematite‐based photoanodes for solar‐fuel devices relying on noncritical elements.