Investigation of Bimetallic Ni-Cr Catalyst for Urea Oxidation in Alkaline Solution

Urea oxidation reaction is the major barrier for widespread commercialization of direct urea fuel cells because of its very sluggish reaction kinetics. In this work, Ni-Cr/C is reported for enhanced performance towards urea oxidation. They are characterized by X-ray diffraction (XRD), inductively coupled plasma-optical emission spectrometer (ICP-OES) and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties towards urea oxidation are evaluated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The amount of the Cr is optimized in the catalysts and it was found that Ni_60-Cr₄₀/C exhibits highest urea oxidation activity of 87 mA cm_geo.^-2 @0.55 V with an onset potential of 0.33 V vs. Ag/AgCl. The chronoamperometric plots suggest catalysts are stable in presence of urea even after 2000 s. The charge transfer resistance with Ni₆₀-Cr₄₀/C is lowest at various bias potential relevant to urea oxidation reaction which is indicative of enhanced conductivity observed from EIS measurements.

Keywords: Ni-Cr/C, urea oxidation, electrochemical impedance spectroscopy, borohydride reduction