Effect of Ni catalysts thickness on performance of Urea- KOH/Ni/PS/Si fuel cells

In this paper fabrication technology and nickel catalyst thickness dependence of output characteristics of direct Urea, KOH and Urea- KOH)/Ni/PS/Si proton exchange membrane type fuel cells are presented. The nominal thicknesses of 10–50 nm nickel as catalyst films and the solutions with concentrations of urea (CO (NH ₂ ) ₂ ) 0.5M, potassium hydroxide (KOH) 3M and Urea 0.5M – KOH 3M as anode electrodes were used in the cells. XRD and spectroscopic ellipsometry measurements were used for nickel catalyst characterization. Effects of nickel catalyst thickness and type of electrodes on maximum power density and open circuit voltage were investigated at room temperature and ambient atmosphere of 30–40% humidity. The best output characteristics of W = 10.5 mW/cm ² and Voc = 0.6 V were observed at urea-KOH electrode and 10 nm of nickel catalyst thickness. Possible reason of this phenomenon is discussed on the basis of size effect, which may occur at ultrathin thicknesses of the nickel catalyst.