Nickel phosphide on Ni foam as anode and peroxymonosulfate as the chemical oxidizer for effective direct urea fuel cell.

The direct urea fuel cell (DUFC) is a low cost and competitive approach for contemporaneous urine or urea-contaminated wastewater treatment and electricity generation. However, the lack of efficient urea oxidation reaction (UOR) electrocatalysts and suitable electron acceptors remains a challenge for practical applications. Here, we developed a DUFC system using NiP@Ni foam as the anode and peroxymonosulfate (PMS) as the chemical oxidizers. The NiP@Ni foam anode showed a high oxidation activity for UOR with an onset potential of 0.30 V vs. Ag/AgCl and Tafel slope of 34.4 mV/dec. PMS with high theoretical potential improved the cell voltage to 1.43 V. A power density of DUFC up to 4.91 mW/cm was achieved using PMS at room temperature, which was approximately twice as high as using HO (2.38 mW/cm). Ni/Ni was the redox active species on the NiP anode in the DUFC process, and Ni was electrochemically oxidized to Ni, which reverted to Ni by urea reduction. When real human urine was used as the fuel, a power density of 4.46 mW/cm can be achieved at room temperature. This DUFC with high cell performance showed potential application in urea wastewater treatment.