  Graphene sponge electrodes were employed for chlorine-free inactivation of
Escherichia coli from low conductivity water. The nitrogen-doped reduced
graphene oxide (NRGO) sponge anode bearing more positive charge achieved
complete E. coli inactivation (i.e., 5 log removal) in the anode-cathode
configuration at 115 A m-2, versus 2.6 log removal using boron-doped reduced
graphene oxide sponge anode. The bacteria were mainly inactivated via
electrosorption and electroporation, as confirmed by the scanning electron
microscopy. Storage of the electrochemically treated samples revealed further
killing of the bacteria due to the damaged cell membranes. When using real tap
water, 5.5 log E. coli removal required 5.70 kWh m-3, which was drastically
lowered to 1.38 kWh m-3 using intermittent current and thus exploiting the
capacitive properties of graphene. The developed graphene sponge anode does not
form any chlorine, chlorate, or perchlorate, and holds great promise for
efficient electro-disinfection without forming toxic disinfection byproducts.
