Electrooxidation of urea and creatinine on nickel foam-based electrocatalysts

Abstract

Electrooxidation of urea and creatinine is desirable for wastewater remediation and portable dialysis to remove the two solutes from aqueous waste streams. Urine concentrations of urea (330 mM) and creatinine (18 mM) are relevant for wastewater remediation while portable dialysis must be able to remove blood serum concentrations of urea (10 mM) and creatinine (0.18 mM) from dialysate. Three nickel foam-based electrocatalysts (clean Ni foam, Ni hydroxide, and Ni hydroxide doped with 1 mol % iron) were examined as substrates for the simultaneous electrooxidation of urea and creatinine. Electrodes were hydrothermally fabricated and characterized by loading, scanning electron microscopy and elemental mapping. Cyclic voltammetry and chronoamperometry were used to electrochemically evaluate the three catalysts. All electrochemical experiments were performed at room temperature and pH 14. The results indicate that creatinine in urea solutions suppresses the oxidation current relative to urea-only solutions on Ni foam and Ni hydroxide catalysts. On iron-doped Ni hydroxide, an enhanced oxidation current occurs in cyclic voltammetry of creatinine/urea solutions, with the effect greater for dialysaterelevant concentrations. In chronoamperometry measurements, a slight decrease in oxidation current is observed for urea/creatinine solutions as compared with urea alone. This behavior is attributed to concurrent reactions of urea and creatinine subject to site blocking by adsorbed creatinine fragments that becomes evident at long time scales.

L-Alanine Supported Autogenous Eruption Combustion Synthesis of Ni/NiO@RuO2 Heterostructure for Electrochemical Glucose and pH Sensor

“…In a negative sweep, two distinct reduction peaks, correspond to the reduction of α-NiOOH →NiO (0.34 V) and γ-NiOOH →NiO (0.22 V) at the electrode surface can be observed, particularly for Ni/NiO catalyst. 74 The decrease in reduction current may be attributed to catalyst consumption during the glucose-to-gluconolactone conversion process. 75 The possible reaction mechanisms are as follows 4-7: 76,77 As depicted in Figs.…”

New Insights into Urea Electro-Oxidation: Complete Mass-Balances and Proof of Concept with Real-Matrix Effluent

“…The initial current density value, after immediate polarization, is higher for urine electrolysis (34 A.m −2 with urea concentration of 0.23 mol.L −1 ) than urea synthetic solution (31 A.m −2 with urea concentration of 0.33 mol.L −1 ), thus suggesting an EC activity at the applied potential other than the one observed between urea and Ni(III)→Ni(II) redox system. This additional activity could be direct or indirect, and would involve other organic molecules present into the urine, as already depicted for creatinine 25 or ascorbic/uric acids and glucose. 26 Immediately after the start of urine electrolysis, the current density decreases more rapidly over time than it does during urea synthetic electrolysis.…”

“…Some previous works have already pointed out this production, such as the formation of cyanate from the oxidation of glycine 28 or the N 2 generated by the oxidation of creatinine. 25,29 Figure 2d shows the molar distribution of the identified species present in the matrix. The term…”

“…In addition, the adsorption on nickel sites of higher size organic molecules (such as creatinine 25 ), limits the urea adsorption on these nickel sites and consequently completely modifies the reaction pathway.…”

Electrochemical oxidation of meglumine in a pharmaceutical formulation using a nanocomposite anode

“…After clinical analysis, the gadolinium-based compounds are excreted unmetabolized through the urine. Where the two most abundant organic compounds are urea and creatinine [24]. Human urine contains about 0.33 M urea [25], which is a source of energy [26].…”