Nano-sized nickel with primary particle size of 2-3 nm has been successfully prepared for use as efficient anode catalysts in urea and urine fuel cells. XRD. SEM and TEM were used for characterisation of nanosized nickel. Based on the previous communication, the performance of urea and urine fuel cells has been further improved when the relative humidity at the cathode was 100%. A maximum power density of 14.2 mW cm(-2) was achieved when 1 M urea was used as fuel, humidified air as oxidant. The performance of urine fuel cells operating above room temperature was also reported for the first time and a power density of 4.23 mW cm(-2) was achieved at 60 degrees C indicating potential application in urea-rich waste water treatment. (C) 2011 Elsevier B.V. All rights reserved.