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

Abstract

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/cm 2 (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/cm 2 (vs. Ag/AgCl)], as determined by cyclic voltammetry and chronoamperometry. A Urea-O 2 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/cm 2 at 25 and 60 • C, respectively, in a 3 M KOH/1 M urea solution.

Spherical Ni/NiO nanoparticles decorated on nanoporous carbon (NNC) as an active electrode material for urea and water oxidation reactions

“…Herein, the urea molecules with electron-donating amino groups and electron-withdrawing carbonyl groups can be selectively adsorbed on NNC via. Ni/ NiOO-carbonyl group as an intermediate step, 5,[26][27][28][29] followed by the corresponding nucleophilic OH − attack. As a result, cleavage of the C-N bond became more favourable, and UOR could proceed at a lower potential.…”

“…To overcome this obstacle, finding alternative strategies to fabricate high-performance OER electrocatalysts is desirable. In recent years, it has been shown that anodic OER can be replaced with electrocatalytic oxidation of small molecules, such as urea, 4 benzyl alcohol, 5 and hydrazine, 6 which can considerably reduce the overpotential required for H 2 production.…”

Ni‐Fe Layered Double Hydroxide Nanosheets Supported on Exfoliated Graphite for Efficient Urea Oxidation in Direct Urea Fuel Cells

“…For instance, the NiÀ Co catalyst was frequently adopted in literature, producing high power outputs ranging from 1.4 to 21.7 mW cm À 2 . [9,10,[20][21][22][23][24][25] Alternatively, NiÀ Cu, [26] NiÀ Pd, [27,28] NiÀ Cr, [29] and Ni-Fe [30][31][32] catalysts have also been explored. Among these Ni-based bimetallic catalysts, a layered double hydroxide (LDH) structure is especially advantageous owning to its unique properties such as tunable metal species and molar ratios.…”