Ni x Co 3-x O 4 nanowire arrays grown on carbon fiber cloth as efficient electrocatalysts for urea oxidation

Hydrothermal synthesis of Mn3O4 nanorods modified indium tin oxide electrode as an efficient nanocatalyst towards direct urea electrooxidation

Control fabrication of metal-oxide nanocatalysts for electrochemical reactions has received considerable research attention. Here, manganese oxide (Mn₃O₄) nanorods modified indium tin oxide (ITO) electrodes were prepared based on the in-situ one-step hydrothermal methods. The nanorods were well characterized using field emission scanning electron microscopy, Fourier transform infrared, and X-ray diffraction spectroscopy. The results showed the formation of pure crystalline Mn₃O₄ nanorods with a length of approximately 1.4 μm and a thickness of approximately 100 ± 30 nm. The Mn₃O₄ nanorod-modified ITO electrodes were used for accelerating urea electrochemical oxidation at room temperature using cyclic and square wave voltammetry techniques. The results indicated that the modified electrode demonstrated excellent electrocatalytic performance toward urea electrooxidation in an alkaline medium over concentrations ranging from 0.2 to 4 mol/L. The modified electrode showed high durability, attaining more than 88% of its baseline performance after 150 cycles; furthermore, the chronoamperometry technique demonstrated high stability. Thus, the Mn₃O₄ nanorod-modified ITO electrode is a promising anode for direct urea fuel cell applications.

Enhanced Electrochemical Properties of Catalyst by Phosphorous Addition for Direct Urea Fuel Cell

An anode bimetallic catalyst comprising Ni-Pd alloy nanoparticles was loaded on acid-treated multi-walled carbon nanotubes (MWCNTs) for application in a direct urea fuel cell. The bimetallic catalyst and MWCNTs were synthesized by a hydrothermal method at 160°C for 5 h. To reduce the catalyst particle size, alkaline resistance, and facilitate their uniform distribution on the surface of the MWCNTs, phosphorus (P) was added to the Ni-Pd/MWCNT catalyst. The effects of P on the distribution and reduction in size of catalyst particles were investigated by Brunauer-Emmett-Teller analysis, transmission electron microscopy, and X-ray diffraction analysis. The enhanced catalytic activity and durability of the P-containing catalyst was confirmed by the high current density [1897.76 mA/cm2 (vs. Ag/AgCl)] obtained at 0.45 V in a 3 M KOH/1.0 M urea alkaline aqueous solution compared with that of the catalyst without P [604.87 mA/cm2 (vs. Ag/AgCl)], as determined by cyclic voltammetry and chronoamperometry. A Urea-O2 fuel cell assembled with a membrane electrode assembly comprising the Ni-Pd(P)/MWCNT catalyst delivered peak power densities of 0.756 and 3.825 mW/cm2 at 25 and 60°C, respectively, in a 3 M KOH/1 M urea solution.