C2h6o2

The (Ce (NO₃)₃.6H₂O, 99.99%), (Fe (NO₃)₃·9H₂O, 98.0%), (ZnSO₄.7H₂O, 98%), (C₆H₈O₇, 99.57%), and (C₂H₆O₂, 99.8%) were purchased from Sigma-Aldrich, Germany and used as received without further purification. The synthesis of ZnCe_xFe_2−xO₄ (X = 0.0, 0.02, 0.04, 0.06, 0.08) powders was carried out using a facile sol–gel method as described in detail in our previous work [10 (link),11 (link),12 (link),25 (link),34 (link),35 (link)].

The following materials were used for synthesis and anion modification of LDHs: Al(NO₃)₃·9H₂O (98.5%, Chempur), Mg(NO₃)₂·6H₂O (99%, Chempur), NaCl (99.9% Chempur), NaH₂PO₄·2H₂O (>98% Carl Roth), Na₂HPO₄·2H₂O (>98% Scharlau), HNO₃ (66%, REACHEM s.r.o.), C₂H₆O₂ (99%, Sigma-Aldrich), HCl (36%, Chempur). Deionised and decarbonised water was used for syntheses, preparation of solutions and washing of final products.

Three different DES electrolytes were used: hydrated 0.3 M ZnSO₄ in reline (abbreviated ChU0.3), anhydrous 0.3 M ZnSO₄ in reline (abbreviated AChU), 0.1 M ZnSO₄ (abbreviated ChU0.1), and 0.3 M ZnSO₄ in ethaline (abbreviated ChEG). Reline was first prepared by combining urea (CO(NH₂)₂, ACS (New York, NY, USA) reagent, 99%) and choline chloride (C₅H₁₄ClNO, Sigma-Aldrich (St. Louis, MO, USA) 99%) (2:1 molar ratio) at a temperature of 70 °C for 1 h until a homogeneous colorless solution was obtained. Then, ZnSO₄ was added to reline to obtain ChU0.3 and ChU0.1 DES electrolytes. A pre-drying process was performed to eliminate the crystallization water of choline chloride, urea and ZnSO₄ powders by heating these powders separately at 120 °C under a rotary-pump vacuum for 2 days. After drying, the chemicals were transferred to an argon-filled glove box for the preparation of anhydrous reline, which was then used for the preparation of AChU. Ethaline was prepared with the same procedure as reline using ethylene glycol (C₂H₆O₂) (reagent plus, ≥99% Sigma-Aldrich) instead of urea. ChU0.3 and ChEG were then selected as electrolytes for the mechanistic studies of Zn electrodeposition reported in Section 2.1 and Section 2.2.