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Reference : UMR7182-CHRCAC-001
Workplace : THIAIS
Date of publication : Monday, May 11, 2020
Scientific Responsible name : Christine Cachet-Vivier / Stéphane Bastide
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
1. Presentation of the subject
The operators of wastewater treatment plants are thinking about innovative treatment concepts that are less costly in terms of energy and allow the valorization of materials (Nitrogen, Phosphorus, etc.) . As far as nitrogen is concerned, it mainly comes from the urea present in large quantities in urine. Its treatment is not totally effective which leads to discharges into rivers and the atmosphere (nitrate, ammonia, nitrogen oxides). One solution would be to collect the urine separately and treat it at source. Among the methods proposed for urea recovery, previous works have shown that it is possible to use an electrochemical treatment based on the oxidation of urea at the anode and the reduction of water at the cathode , the overall process being:
CO(NH2)2 + H2O CO2 + N2 + 3 H2
This reaction has several advantages: (i) the removal of urea is coupled with the production of dihydrogen (energy recovery), (ii) the dihydrogen is safely storable and transportable and can be used in fuel cells, (iii) urea is available in large quantities in wastewater, (iv) the oxidation products are non-toxic (nitrogen and carbonates) .
Within this framework, the first part of the thesis will be to develop new electrode materials (anode/cathode) for urea conversion that are highly efficient, selective and stable. A second part will be dedicated to the implementation of urea solution electrolysis and then synthetic or real urine electrolysis. The aim will be to identify the reaction products by different analytical means, to establish material and faradaic balances for different configurations and material compositions.
2. Thesis program
The first part of the thesis will consist in developing new anode materials based on MxNi1-x (M being a noble metal) for urea oxidation and cathode materials based on MoxNi1-x for water reduction. These materials, of different compositions, will be prepared in order to obtain alloys or bi-metallics . The parameters to be controlled are crystallinity and nanostructuration, which will be determined by X ray diffraction and Scanning Electron Microscopy, respectively. The electrochemical properties with respect to urea oxidation will be evaluated by voltammetry and chronoamperometry in order to select the best performing materials in terms of efficiency and stability.
The second part of the thesis will be devoted to the implementation of preparatory electrolysis of alkaline solutions of urea in test cells at laboratory level, working under controlled potential or intensity. The reaction products will be identified by different analytical means (gas chromatography, UV-visible spectrometry, HPLC), in order to determine the material and faradaic efficiencies. The results will be related to the different configurations and compositions of the materials. After use, the electrode materials will be characterized by SEM, XPS and Complex Impedance Spectroscopy to study the evolution of their properties and to consider reactivation procedures, if necessary. Electrolysis will then be carried out on synthetic and real urine solutions to highlight the role of ions or molecules present in urine (chlorides, creatine, etc.), both on the products formed and the activity of the electrodes.
 Investigation of multi-metal catalysts for stable hydrogen production via urea electrolysis, R.L. King, G.G. Botte, J. Power Sources 196 (2011) 2773.
 Electrochemical oxidation of urea on nickel-rhodium nanoparticles/carbon composites, P. Mirzaei, S. Bastide, A. Dassy, R. Bensimon, J. Bourgon, A. Aghajani, C. Zlotea, D. Muller-Bouvet, C. Cachet-Vivier, Electrochimica Acta 297 (2019) 715.
The thesis will take place at the Institut de Chimie et des Matériaux Paris-Est (ICMPE), located in Thiais (94). ICMPE (UMR 7182) is under the supervision of the CNRS and the University Paris Est Créteil. It hosts about 100 permanent staff members. The research areas cover three major cross-cutting themes: (i) materials for structures and energy, (ii) molecules, materials and processes for the environment and sustainable development, (iii) chemistry for health at the interface with life.
The PhD thesis will be developed more particularly in the group of Photo/Electrocatalysis for Energy and the Environment and will benefit from the technical support of two ICMPE technological platforms (Elaboration and Characterization of materials). It is part of the ANR HYUREA project (N° 19-CE04-0009-01) and will also be carried out in collaboration with LISE (Laboratoire Interfaces et Systèmes Électrochimiques, CNRS - Sorbonne University) for the characterization by Complex Impedance Spectroscopy.
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