context: The M2+–Fe LDHs (M = Ni, Zn) nanosheets were prepared using a facile electrosynthesis method. Typically, nickel foam (NF, 10 × 30 × 0.05 mm3) was sonicated in 2 M HCl solution for 15 min and subsequently rinsed with water and ethanol to ensure a clean surface. The electrodeposition was carried out in a standard three-electrode system cell containing NF as the working electrode, Pt plate as the counter electrode and Ag/AgCl (3 M KCl) as the reference electrode. The electrolyte for the electrosynthesis of NiFe LDH contained Ni(NO3)2·6H2O (0.03 M) and Fe(NO3)3·9H2O (0.01 M). The total cation concentration in the electrolyte was maintained at 0.04 M. The potentiostatic deposition was then carried out at −1.0 V vs. Ag/AgCl for 300 s at room temperature. The obtained NiFe LDH nanosheets were carefully withdrawn and rinsed thoroughly with water and ethanol and left to dry at 45 °C. The NiZnFe LDHs nanosheets were prepared via a similar method, by replacing Ni(NO3)2·6H2O (0.03 M) with a mixture of Ni(NO3)2·6H2O (0.027 M) and Zn(NO3)2·6H2O (0.003 M).
answer: Ni(NO3)2·6H2O (0.03 M) and Fe(NO3)3·9H2O (0.01 M)