A new catalyst for urea oxidation: NiCo2S4 nanowires modified 3D carbon sponge

Urea oxidation is a significant reaction for utilizing urea-rich wastewater or human urine as sustainable power sources which can ease the water eutrophication while generate electricity. A direct urea-hydrogen peroxide fuel cell is a new kind of fuel cell employing urea as fuel and hydrogen peroxide as oxidant which possesses a larger cell voltage. Herein, this work tries to promote the kinetics process of urea oxidation by preparing low-cost and high-efficient NiCo2S4 nanowires modified carbon sponge electrode. The carbon sponge used in this work with a similar three-dimensional multi-channel structure to Ni foam, is prepared by carbonizing recycled polyurethane sponge which is also a process of recycling waste. The performance of the prepared catalyst in an alkaline solution is investigated in a three-electrode system.With the introduction of Co element to the catalyst, a reduced initial urea oxidation potential and a high performance are obtained. Furthermore, a direct urea-hydrogen peroxide fuel cell is assembled using the NiCo2S4 nanowires modified carbon sponge anode. Results indicate that the prepared catalyst provides a chance to solve the current problems that hinder the development of urea electrooxidation(high initial urea oxidation potential, low performance, and high electrode costs).

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 Ni2 P@Ni foam as the anode and peroxymonosulfate(PMS) as the chemical oxidizers.The Ni2 P@Ni foam anode showed a high oxidation activity for UOR with an onset potential of 0.30 V vs. Ag/Ag Cl and Tafel slope of 34.4 m V/dec. PMS with high theoretical potential improved the cell voltage to 1.43 V. A power density of DUFC up to 4.91 m W/cm2 was achieved using PMS at room temperature, which was approximately twice as high as using H2 O2(2.38 m W/cm2). NiII/NiⅢwas the redox active species on the Ni2 P anode in the DUFC process, and NiIIwas electrochemically oxidized to NiⅢ, which reverted to NiII by urea reduction. When real human urine was used as the fuel, a power density of 4.46 m W/cm2 can be achieved at room temperature. This DUFC with high cell performance showed potential application in urea wastewater treatment.