Salinity gradient energy harvesting via high concentration response characteristics of activated carbon

The main problem of salinity gradient energy extraction using activated carbon (AC) as electrode is charge leakage. We used the chemical charging method to chemically modify the activated carbon electrode so that its surface carries different charged groups. Activated carbon electrodes with different charged properties show strong concentration response. We treated the activated carbon with nitric acid, then chemically modified it with 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC) and 1-aminopropyl-3-methylimidazolium bromide (APMIB) to obtain a positively charged AC-P electrode material with brominium groups on the surface; The activated carbon treated with nitric acid was mixed with a hydrophilic charged polymer binder modified with carboxy methyl cellulose (CMC) by sulfosuccic acid (SSA), and an AC-S electrode material with negative surface sulfonic groups was obtained. These two methods are used to regulate the charge properties on the surface of activated carbon, improve the hydrophilicity and ion selectivity of activated carbon electrode, and the electrode materials show different concentration response effects. By assembling activated carbon materials AC-P and AC-S carrying positive and negative charged groups respectively into capacitors AC-P//AC-S, salinity gradient energy extraction is carried out by four-step cycle method without charging and 2.69 J m−2 energy is obtained. The extraction of salinity gradient energy from common activated carbon was realized after chemical modification.