High lignin containing hydrogels with excellent conducting, self-healing, antibacterial, dye adsorbing, sensing, moist-induced power generating and supercapacitance properties

Herein, we design a dynamic redox system of using high contents of lignosulfonate (LS) and Al3+ to prepare poly acrylic acid (PAA) (LS-g-PAA-Al) hydrogels. The presence of high LS and Al3+ contents, in combination with the effective Al3+ complexes formed, renders the resultant hydrogel with some unique attributes, including excellent ionic conductivity (as high as 7.38 S.m(-1)) and antibacterial activity; furthermore, a very fast gelation (in 1 min) was obtained. As a flexible strain sensor, the LS-g-PAA-Al hydrogel with high conductivity demonstrates superior sensitivity in human movement detection. In addition, the rich anionic hydrophilic groups, such as sulfonic groups, phenolic hydroxyl groups, in the hydrogels impart the resultant hydrogels with excellent adsorption capacity for cationic dyes: when using Rhodamine B (RB) as a model cationic dye, the adsorption capacity of the resultant hydrogel reaches 334.64 mg.g(-1); as a moist-induced power generator, it generates maximum 150.5 mV open circuit voltage with moist air flow. When the hydrogel electrolyte is assembled into a supercapacitor assembly, it shows high specific capacitance of 245.4 F.g(-1), with the maximum energy density of 21.8 Wh.kg(-1), power density of 2.37 kW.kg(-1), and capacitance retention of 95.1% after 5000 consecutive charge-discharge cycles.

Automated summary

In this study, a dynamic redox system utilizing high contents of lignosulfonate (LS) and Al3+ was designed to prepare poly acrylic acid (PAA) hydrogels. The resulting hydrogels exhibited excellent ionic conductivity, antibacterial activity, fast gelation, superior sensitivity as a strain sensor, and excellent adsorption capacity for cationic dyes. Furthermore, the hydrogel electrolyte assembled into a supercapacitor assembly showed high specific capacitance and energy density, with good capacitance retention after repeated charge-discharge cycles.