Encapsulation of a living bioelectrode by a hydrogel for bioelectrochemical systems in alkaline media

The electroactive biofilms in the bioelectrodes of traditional bioelectrochemical systems (BES) directly interact with the aqueous solution and usually require a mild aqueous solution environment (e.g. 20 mM acetate and pH = 7.0) to exert their optimum bioelectrocatalytic activity. In this communication, we present a concept of encapsulation of a bioelectrode by a hydrogel for a BES in an alkaline solution environment. A hydrogel-bioelectrode (HBE) was prepared by encapsulating a living electroactive biofilm pre-grown in the bioelectrode with a poly(vinyl alcohol) hydrogel through a freezing/thawing process. Under the protection of the hydrogel, the HBE could keep a high bioelectrocatalytic activity in an alkaline feeding solution with an acetate concentration of over 80 mM and a pH value of 11.0. Moreover it was very stable and tolerated low-frequency ultrasonic vibration. These results imply the extended applications of BESs in the area of high-strength wastewater treatment, portable and implantable devices.