A urine/Cr(VI) fuel cell — Electrical power from processing heavy metal and human urine

• Electrooxidation of neat urine on Nano-Ni catalyst
• Electroreduction of acidic Cr(VI) at catalyst-free cathode
• Wastewater treatment with direct electricity generation
• Anion/cation hybrid ion exchange membranes as separator

This work shows a strategy of reducing Cr(VI) by human urine with self-generation electricity via a urine/Cr(VI) fuel cell (UCrFC), in which urine functions as fuel and Cr(VI) severs as oxidant. Fresh urine is electro-oxidized on carbon supported nano-Ni catalyst at anode and strong acidic Cr(VI) synthetic wastewater is electro-reduced at catalyst-free cathode. An ion selective separator, consisting of an anion exchange membrane and a cation exchange membrane, is introduced to improve the cell performance by hindering the crossover of dichromate and ammonium. Using 50 mg L− 1 Cr(VI) in 0.25 M H2SO4 as catholyte, neat urine as anolyte, the maximum power density of UCrFC reached 3.4 W m− 2 with an open circuit voltage (OCV) of 1.3 V. More than 90% of Cr(VI) was reduced with coulombic efficiency of more than 98%, meanwhile total carbon and nitrogen in urine was also removed with efficiency about 78%. The effects of initial Cr(VI) and H2SO4 concentration were investigated. The specific capacity of UCrFC reached 4417 mAh per liter of human urine.

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