Nickel/nickel oxide nanocrystal nitrogen-doped carbon composites as efficient electrocatalysts for urea oxidation

The key problem to be solved for the large-scale commercial application of direct urea fuel cells (DUFCs) is to develop a highly efficient catalyst for urea oxidation reaction (UOR). Some drawbacks such as scarcity and poor catalytic performance limit the application of noble metal-based catalysts in the oxidation of urea, it is particularly necessary to design and synthesize non-noble metal-based catalysts with good catalytic performance. In this work, we have fabricated Ni-based composites (Ni/NiO-N-C) through the pyrolysis of the precursor Ni(OH)2@PPH (polyaniline-polyvinyl alcohol hydrogels). The optimal Ni/NiO-N-C-500 catalyst displays an excellent activity of 182 mA cm−2 at 0.6 V vs SCE for UOR in alkaline media. Meanwhile, Ni/NiO-N-C-500 also indicates excellent stability after 1000 cycling CV tests (81% capacitance retention), which is attributed to the synergy between Ni/NiO nanocrystalline active centers and nitrogen-doped carbon substrate, that is, N-doped carbon layers improve the surface electron density and the electrical conductivity of the composite catalyst, thus leading to the improvement of the catalytic activity of catalyst. On account of its easy synthesis, high activity and good durability, the Ni/NiO-N-C-500 catalyst has the potential to act as a good alternative material for precious metal-based catalysts in DUFCs.