Stoichiometry-controlled binder-free NiFe LDH nanoflowers for efficient overall water splitting

Abstract

Designing low-cost, active, and stable bifunctional electrocatalysts with controlled stoichiometry and crystalline precision remains a significant challenge in advancing electrochemical water splitting for efficient hydrogen production. Herein, we report the high-performance electrocatalysts of stoichiometry-controlled binder-free NiFe layered double hydroxide (LDH) nanoflowers, which were directly grown on a nickel foam substrate by a facile hydrothermal method. By varying the reaction temperatures (60-210 C-degrees), the morphology, crystallinity, and oxidation states of NiFe LDH were effectively tuned. This stoichiometric tuning had a significant influence on catalytic behavior, yielding outstanding bifunctional activity. Among all samples, the 150 C-degrees-synthesized NiFe LDH catalyst exhibited optimized oxidation states and uniform morphology with ultrathin nanosheets-laced spherical nanoflowers. The sample showed low overpotentials, small Tafel slope values, and excellent durability in both hydrogen/oxygen evolution reactions in alkaline medium. This eventually resulted in outstanding overall water-splitting performance, achieving an impressively low full-cell voltage of 1.56 V at 10 mA/cm(2) and excellent long-term cell stability observed only <1 % degradation after 100 h. These results suggest that tuning the morphology and stoichiometry of NiFe LDHs via controlling hydrothermal reaction temperatures can offer a simple, scalable, and cost-effective strategy for materializing high-performance catalysts for advanced overall water electrolysis technology.