Decoding Multimetal Synergy in Ternary LDHs for Water Splitting: Experimental and Theoretical Insights.

Trimetallic layered double hydroxides offer a promising advancement over conventional bimetallic systems for alkaline water electrolysis. The incorporation of a third metal can introduce additional electronic modulation and synergistic interactions, potentially enhancing catalytic activity and stability. However, despite these advantages, bimetallic LDHs still dominate the field of electrocatalysis and remain the "uncrowned kings" among LDH-based catalysts. So, what limits the effective utilization of ternary metal systems? In this work, NiFe and NiFeCr LDHs were rationally designed as efficient bifunctional electrocatalysts. The strategic incorporation of Cr based on its favorable work function and electronic compatibility with Ni and Fe was analyzed with the help of density functional theory (DFT). The NiFeCr LDH demonstrated a significantly enhanced electrochemically active surface area, providing abundant redox-active sites for both oxygen and hydrogen evolution reactions. To enhance conductivity and structural integrity, a nanocomposite was engineered further by integrating β-FeOOH with a beautiful tunnel-like crystal structure and superior electron transport properties. This β-FeOOH/NiFeCr LDH hybrid strengthens the internal synergy and facilitates enhanced charge transfer and redox kinetics. This results in the system's improved electrical and structural characteristics, which are thoroughly examined in this paper using a comprehensive experimental and theoretical analysis. The cell constructed using the fabricated bifunctional catalyst shows an overpotential of 484 mV to reach a current density of 50 mA/cm2 in 1 M KOH. This study offers a comparative analysis of the efficiency and robustness of ternary and binary LDH composites and how synergy works in the interface for improved redox kinetics.