Electrochemical impedance spectroscopy (EIS) measurements were done at open circuit potential (OCP) conditions, using perturbation peak-to-peak amplitude 10 mV and frequencies from 100 kHz to 100 mHz, 12 points per decade, after 5 min initial conditioning. Next, cyclic voltammetry (CV) measurements were carried out in the polarization range from -0.2 to 1.0 V, vs Ag|AgCl. Different scan rates, from 10 to 1000 mV/s, were employed. Chronoamperometry (CA) tests were performed at applied voltages of +300 mV, +400 mV, and +500 mV, vs. Ag|AgCl for LIGs, and screen-printed carbon electrodes (SPCEs and DropSens 150, purchased from Metrohm), for reference. SPCEs were covered by 2.7 µL of CS or Alg solutions (0.2%) followed by drop-casting 2.7 µL of glutaraldehyde (3%) or a CaCl2 (100 mM) solution, respectively. For making Agar coated SPCEs, 2.7 µL of Agar solution (0.2%) was drop cast on the SPCEs and left to dry under environmental conditions. For CA measurements, one droplet (100 µL) of 10 mM PBS solution containing 5 mM Fe(CN)6 4-redox probe was poured onto the SPCE or coated SPCEs and the experiments continued for 2 minutes.