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A free-standing catalyst electrode for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) in a urea electrolysis cell was synthesized by electroplating a Ni–Fe alloy onto carbon felt, followed by phosphidation (P-NiFe@CF). The prepared P-NiFe@CF catalyst consisted of Ni5P4, NiP2, and FeP with 3D flower-like P-NiFe architecture on CF. P-NiFe@CF exhibited excellent electrocatalytic activity for the UOR (demanding only 1.39 V (vs. RHE) to achieve 200 mA cm−2), and for the HER with a low overpotential of 0.023 V (vs. RHE) at 10 mA cm−2, indicating its feasibility as a bifunctional catalyst electrode for urea electrolysis. A urea electrolysis cell with P-NiFe@CF as both the free-standing anode and cathode generated a current density of 10 mA cm−2 at a cell potential of 1.37 V (vs. RHE), which is considerably lower than that of water electrolysis, and also lower than previously reported values. The results indicate that the P-NiFe@CF catalyst electrodes can be used as free-standing bifunctional electrodes for urea electrolyzers. [ABSTRACT FROM AUTHOR]

Urea splitting to produce H 2 is as an energy-saving alternative to water electrolysis. However, efficient catalysts are required for the practical implementation of urea splitting because of the high overpotentials of the urea oxidation reaction and the hydrogen evolution reaction. Herein, a Ni-modified direct Z-scheme photocatalyst for the urea oxidation and hydrogen evolution reactions was synthesized by electroplating a WO 3 /g-C 3 N 4 nanocomposite on Ni-decorated carbon felt (WO/CN–Ni@CF). The 2D/2D nanostructure of the as-synthesized WO 3 /g-C 3 N 4 composite was confirmed by SEM and TEM. The WO/CN–Ni@CF catalyst electrode exhibited excellent bifunctional photocatalytic activity for the urea oxidation and hydrogen evolution reactions. Consequently, the potential required to generate 100 mA cm−2 in an illuminated photoelectrochemical cell using WO/CN–Ni@CF as the anode and the cathode was reduced from 1.80 to 1.50 V. The photoelectrochemical cell exhibited good stability for 18 h with stable H 2 generation. [Display omitted] • WO 3 /g-C 3 N 4 nanocomposite as Z-scheme photocatalyst for urea splitting. • The photocatalyst was electrospun onto Ni-plated carbon felt (WO/CN–Ni@CF). • The WO/CN–Ni@CF exhibited excellent bifunctional photocatalytic activity. • The required potential in UOR∥HER was considerably reduced by solar illumination. [ABSTRACT FROM AUTHOR]

A highly porous free-standing NiCr-bimetallic catalyst is synthesized by electrospinning and carbonization and is applied as an anode in a direct urea/H 2 O 2 fuel cell for electro-oxidation of urea. It is observed that the morphology of the calcined NiCr catalyst, which has a higher specific surface area, is identical to that of the electrospun NiCr catalyst fiber. Cr-doping at 40% (Cr/Ni) significantly increases the oxidation peak current of the urea oxidation reaction. The addition of carbon nanotubes also considerably enhances the catalytic activity. A direct urea/H 2 O 2 fuel cell, which utilizes the synthesized catalyst (NiCr-CNT@C) as a free-standing anode, exhibits excellent performance with a maximum power density of 48.1 mW cm−2 and an open-circuit voltage of 0.92 V at 80 °C. Thus, the highly porous free-standing NiCr-CNT@C catalyst mat can be employed as an efficient anode material for urea oxidation in urea fuel cells. Image 1 • A freestanding NiCr catalyst mat was synthesized by electrospinning technique. • NiCr bimetal nanoparticles were uniformly embedded in the carbon nanofibers. • The NiCr catalyst featured excellent electro-catalytic activity for urea oxidation. • A urea fuel cell with NiCr catalyst exhibited a power density of 48.1 mW cm−2. [ABSTRACT FROM AUTHOR]