Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm⁻² when 0.33 M urea was used as fuel, O₂ as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm⁻² with an open circuit voltage of 0.38 V at 60°C.

Urea is a safe and sustainable chemical for electrochemical energy conversion and storage. However, the sluggish kinetic rates of the electrooxidation reaction of urea as well as catalyst stability still remain to be challenges. In this work, we investigated several catalysts for the electro-oxidation of urea by directly growing NiM double hydroxides (M = Cr, Mn, Fe, Co, Cu, Zn) on carbon fibre cloth and nickel foam electrodes through a facile one-step hydrothermal synthesis method. The results indicated that the activity was significantly related to the elemental composition. Among the investigated double hydroxides, the NiFe double hydroxide (DH) catalyst showed the highest activity, which achieved a specific current density of ∼95 mA cm⁻² mg⁻¹ at 0.5 V vs. Ag/AgCl, about 10 times larger than that of Ni(OH)₂. In addition, the NiFe DH also had a high activity when grown on a Ni foam substrate. This NiFe DH performs well in the aspect of urea oxidation stability, demonstrating it to be a promising low-cost and stable catalyst for the efficient electrooxidation of urea under alkaline conditions.

Potential dependent in situ Raman spectra confirm that Mn doping enables a negative shift in Ni(ii) oxidation onset potential.

Attempts were made to culture Spirulina platensis in human urine directly to achieve biomass production and O(2) evolution, for potential application to nutrient regeneration and air revitalization in life support system. The culture results showed that Spirulina platensis grows successfully in diluted human urine, and yields maximal biomass at urine dilution ratios of 140 approximately 240. Accumulation of lipid and decreasing of protein occurred due to N deficiency. O(2) release rate of Spirulina platensis in diluted human urine was higher than that in Zarrouk medium.