Synthesis and Electrocatalytic Activity of Ammonium Nickel Phosphate, [NH₄]NiPO₄·6H₂O, and β-Nickel Pyrophosphate, β-Ni₂P₂O₇: Catalysts for Electrocatalytic Decomposition of Urea

Abstract

Electrocatalytic decomposition of urea for the production of hydrogen, H for clean energy applications, such as in fuel cells, has several potential advantages such as reducing carbon emissions in the energy sector and environmental applications to remove urea from animal and human waste facilities. The study and development of new catalyst materials containing nickel metal, the active site for urea decomposition, is a critical aspect of research in inorganic and materials chemistry. We report the synthesis and application of [NH]NiPO·6HO and β-NiPO using in situ prepared [NH]HPO. The [NH]NiPO·6HO is calcined at varying temperatures and tested for electrocatalytic decomposition of urea. Our results indicate that [NH]NiPO·6HO calcined at 300 °C with an amorphous crystal structure and, for the first time applied for urea electrocatalytic decomposition, had the greatest reported electroactive surface area (ESA) of 142 cm/mg and an onset potential of 0.33 V (SCE) and was stable over a 24-h test period.

Ultrathin nickel-metal–organic framework nanobelt based electrochemical sensor for the determination of urea in human body fluids

“…At the same time, the peak current response heightens conspicuously in the anode and weakens in the cathode when 1.0 mM urea was injected (curve a). It has been reported that a cost-effective nickel-based catalyst can convert urea into non-poisonous and harmless nitrogen gas products under alkaline conditions by electro-oxidation, 25 and the electrocatalytic process of this material towards urea may occur as follows: 8,17,20,26 Ni…”

“…The DPV measurements manifest that the electrooxidation course keeping accordance with the switch from Ni(II) to Ni(III) is affected by the increasing concentration of urea and it is simultaneously electro-oxidized to nitrogen gas in this process. 25 Linear sweep voltammetry response of urea. Linear sweep voltammetry (LSV), similar to cyclic voltammetry (CV), is also a kind of common electrochemical test means, which is oen used for quantitative determination of adsorbent substances.…”

Co2P2O7–Ni2P2O7 solid solutions: Structural characterization and color

“…The study and development of new catalyst materials containing nickel metal, the active site for urea decomposition, is a critical aspect of research in inorganic and materials chemistry. The [NH 4 ]NiPO 4 ·6H 2 O calcined at 300°C with an amorphous crystal structure has the greatest reported electroactive surface area (ESA) of 142 cm 2 /mg and an onset potential of 0.33 V (SCE) and was stable over a 24‐hour test period …”

“…The α → β transition occurs at 573 K when M = Co and at 838 K when M = Ni . In the β‐M 2 P 2 O 7 (M = Co, Ni) monoclinic structure, with Z = 2 and standard space group C 1 2/m 1, all M(II) ions are in octahedral sites and all P(V) are in tetrahedral sites.…”

Porous rod-like Ni2P/Ni assemblies for enhanced urea electrooxidation

“…Because Ni 2+ oxidizes to Ni 3+ more easily before the reaction starts, more electroactive sites will be obtained [20][21][22]. Compared with NiO, which is a typical electrocatalytic material for UOR, the energy of Ni2P is significantly lower, because of the lower energy of the Ni-P bond compared to that of Ni-O [23][24][25]. Nevertheless, the weak stability hinders its wide application.…”