Ni-WC/C Catalyst Synthesized From Ammonium Paratungstate for Urine Fuel Cell

As global warming and climate change caused by fossil fuel grew to be a public concern, find a clean and sustainable substitute energy had become a scientific hotspot. Urea is a hydrogen carrier which makes it a feasible energy source. The urea-rich wastewater or urine which normally contains 0.33 M urea were used as fuels, which can generate electricity while processing wastewater to reduce water pollution and others. Moreover, It is considered to have a great application in aerospace to recycle the urine produced by astronauts.

Furthermore, non-precious metal catalyst, such as nickel, is active for urea electrooxidation, which offers the possibility of reducing the cost of fuel cells without using precious metals.. Unfortunately, the initial reaction kinetics is relatively slow due to the limited amount of NiOOH and the reaction rate quickly decreases.

To get over the disadvantages, Ni-WC/C catalyst was synthesized from ammonium paratungstate (APT) for urine fuel cell applications, as the activity and stability for urea electrooxidation were enhanced.

The synthesis process Ni-WC/C catalyst is as below:

The Ni-WC/C catalyst was prepared using a sequential impregnation method. First, activated carbon was put in an ammonium paratungstate aqueous solution followed by a temperature-programming reduction (TPR) treatment with CH4 and H2 to obtain WC/C. It was then impregnated in a nickel nitrate aqueous solution with another TPR treatment to produce the Ni-WC/C catalyst. The Ni content of Ni-WC/C catalyst is 20%. The TPR procedures were the same as reported previously. XRD patterns were obtained using a Rigaku D/max-2400 with a Cu Kα radiation source to determine the crystalline structures.

In summary, Tungsten carbide modified nickel (Ni-WC/C) catalyst is synthesized through the sequential impregnation method led to enhanced activity and stability for urea electrooxidation. Furthermore, the introduction of WC also enhances the anti-poisoning ability, thus promoting more complete oxidation of urea to produce CO2, which leads to a higher energy conversion efficiency than that on Ni/C. Electrochemical active surface area and specific activity all increased on the Ni-WC/C electrode. This work provides a new strategy for designing highly efficient catalysts for urea electrooxidation.

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