Ta-NiFe-LDH@La-ZIF-67 Composite Heterostructures for Efficient Electrocatalytic Hydrogen Generation and Overall Water Splitting

In this work, we demonstrated the high activity and stability of the Ta-NiFe-LDH@La-ZIF-67 heterostructure for HER electrocatalysis and overall water splitting. The catalyst obtained by partial in situ coprecipitation coupled with a solvothermal process maintained 96.66% activity retention over a 48 h i-t stability test. A retention percentage of 77.92% was achieved over 24 h at 60 mA/cm2. It required only 109 and 1.63 V vs RHE to produce 10 mA/cm2 during HER and overall water splitting in 1 M KOH, respectively. Linear sweep voltammetry (LSV) revealed negligible degradation (Δη = 10 mV) after 1500 cycles. Moreover, Ta-NiFe-LDH@La-ZIF-67 exhibited a large electrochemically active surface area (1121.75 cm2) and a small Tafel slope (36.26 mV/dec), indicative of a Volmer–Tafel mechanism. The interfacial coupling between Ta-NiFe-LDH and La-ZIF-67 enhanced charge transport and improved catalytic kinetics. Stability was ensured by mutual component stabilization and the incorporation of Ta5+ ions. The Ta5+ and La3+ doping induced defect formation, and optimized water dissociation kinetics and OH– adsorption. The hydrogen-binding optimization was achieved through electronic coupling, and the hierarchical porosity ensured a rapid mass transport. This work defines a design paradigm for MOF/Layered double hydroxide heterostructures for applications in next-generation water splitting.