Synthesis and performance evaluation of various metal chalcogenides as active anodes for direct urea fuel cells

Metal chalcogenides have received significant attention as electro-catalysts in different applications, due to their superior electrical conductivity and good thermal and mechanical stabilities. In this work, the optimum monocrystalline Ni-P and Ni-C, C (Se, S, O) nanosheet (NS), prepared on nickel foam as standalone anodes for urea fuel cells was introduced. The activity was investigated ex-situ and in-situ the cell. The results demonstrated that the non-oxide metal forms, i.e., Ni-P, Ni-S, and Ni-Se, have superior oxidation activity than the Ni layered double hydroxide (Ni-LDH) and Ni-O. In addition, Ni-Se showed the most superior urea oxidation activity among all prepared catalysts. Although the onset potential of all the samples was around 0.35 V vs Ag/AgCl, a steady current of 195 mAcm(-2) was recorded after 120 min using Ni-Se, which is two times higher than that of Ni-S, five times higher than Ni-O, and ten times higher than Ni-LDH. The superior activity of the Ni-Se was related to its unique crystalline structure and the high porous morphology. The performance of Ni-Se electrode under actual direct urea fuel cell (DUFC) operation using a nonprecious a Prussian blue cathode revealed 33 mWcm(-2) power, which is, one of the highest power outputs in DUFCs equipped with Ni-based anodes at room temperature, as far as the authors know.

Automated summary

Metal chalcogenides have been widely studied as electro-catalysts due to their superior electrical conductivity and stability. In this research, Ni-Se monocrystalline nanosheet anodes showed outstanding urea oxidation activity, outperforming other catalysts. The high activity of Ni-Se was attributed to its unique crystalline structure and high porous morphology.