Studies on Pulse Electrodeposition of Pt-Ni binary Alloy For Electrochemical Cell Applications

The possibility to prepare a Pt-Ni bimetallic catalyst for electrochemical cells applications using a two-step electrochemical process was tested. The binary alloy catalyst was deposited on a graphitic substrate covered with carbon nanofibers previously treated in oxygen plasma. This support system provides a high surface area for the alloy particles, improving considerably the catalytic activity. A simultaneous reduction reaction of Pt and Ni was performed by strictly controlling the metals ratios in the solution and by choosing suitable deposition parameters. A pulsed current technique was applied. Varying the Pt: Ni ratio in the electrolyte and adjusting the deposition main parameters lead to a homogeneous distribution of the catalyst. A comparison with pure platinum nano-scaled supported electrodes is also presented, regarding hydrogen/oxygen evolution reaction. Although a significant decrease of platinum amount was achieved by alloying, a higher activity of the catalyst was obtained. Morphology, structure, and chemical composition of the catalysts was investigated by means of scanning electron microscopy combined with energy dispersive X-ray spectroscopy. X-ray diffraction was used to identify the alloy phase composition. The amount of deposited alloy determined using thermogravimetric measurements correlated with the cyclic voltammetry performed in 0.5 M H₂SO₄ solution to estimate the electrochemical surface area offered important information regarding the catalytic activity. (paper)