Applications of Nickel–iron Layered Double Hydroxides with Different Ni:Fe Ratios for CO2 Adsorption and Alkaline Water Electrolysis

To mitigate the global climate crisis and address the growing demand for environmental monitoring, in this study, we developed Ni-Fe layered double hydroxides (LDHs) with molar ratios of 2:1, 2.5:1, and 3:1 as a multifunctional platform for CO 2 capture, green hydrogen production, and advanced sensing applications.Characterization analysis confirmed the formation of ordered 2D nanosheets with an average size of ~300 nm, providing an optimal high-surface-area matrix for both catalytic and sensing interfaces.For carbon capture, the Ni-Fe LDH with a Ni:Fe molar ratio of 2:1 functionalized with 20 wt% tetraethylenepentamine achieved a peak uptake of 0.389 g CO 2 /g, significantly outperforming other compositions owing to Fe 3+ -enhanced Lewis acidity and hydroxyl density.Crucially, this extraordinary capture capacity translates into a massive mass-loading response, demonstrating its immense potential as an ultrasensitive recognition layer for gravimetric CO 2 gas sensors.Regarding electrolysis, the Ni-Fe LDH-coated nickel foam with a Ni:Fe molar ratio of 2:1 yielded 50 mL of H 2 over 15 h, representing an 11% improvement over bare nickel foam.Furthermore, this architecture maintained the lowest charge-transfer resistance (Rct), making it a highly promising conductive substrate for future electrochemical sensing.These results prove the 2:1 Ni:Fe ratio to be the optimal configuration for integrated carbon mitigation, clean energy production, and environmental monitoring technologies.