1. Self-adaptive amorphous CoOxCly electrocatalyst for sustainable chlorine evolution in acidic brineMengjun Xiao, Qienbao Wu, Ruiqi Ku, Liujiang Zhou, Chang Long, Junwu Liang, Andraž Mavrič, Lei Li, Jing Zhu, Matjaz Valant, Jiong Li, Zhenhua Zheng, Chunhua Cui, 2023, izvirni znanstveni članek Opis: Electrochemical chlorine evolution reaction is of central importance in the chlor-alkali industry, but the chlorine evolution anode is largely limited by water oxidation side reaction and corrosion-induced performance decay in strong acids. Here we present an amorphous CoOxCly catalyst that has been deposited in situ in an acidic saline electrolyte containing Co2+ and Cl- ions to adapt to the given electrochemical condition and exhibits ~100% chlorine evolution selectivity with an overpotential of ~0.1 V at 10 mA cm−2 and high stability over 500 h. In situ spectroscopic studies and theoretical calculations reveal that the electrochemical introduction of Cl- prevents the Co sites from charging to a higher oxidation state thus suppressing the O-O bond formation for oxygen evolution. Consequently, the chlorine evolution selectivity has been enhanced on the Cl-constrained Co-O* sites via the Volmer-Heyrovsky pathway. This study provides fundamental insights into how the reactant Cl-itself can work as a promoter toward enhancing chlorine evolution in acidic brine.
Ključne besede: Catalyst synthesis, Electrocatalysis, Chlorine evolution
Objavljeno v RUNG: 04.09.2023; Ogledov: 153; Prenosov: 2
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2. Iron phosphide as an efficient electrocatalysts for hydrogen evolution : abstractTakwa Chouki, Manel Machreki, Saim Emin, 2020, objavljeni povzetek znanstvenega prispevka na konferenci Opis: We report the solvothermal synthesis of iron phosphide electrocatalysts using a low-cost phosphorus precursor. The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe2P−450°C, Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M sulfuric acid (H2SO4). The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The present approach allows preparation of immobilized iron phsphide catalyst onto carbon support which is essential for application purpose. The procedure developed by us is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles
Ključne besede: solvothermal synthesis
iron phosphide
electrocatalysis
HER
Objavljeno v RUNG: 06.02.2023; Ogledov: 560; Prenosov: 0
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3. Efficient Iron Phosphide Catalyst as a Counter Electrode in Dye-Sensitized Solar Cells : articleAbdullah Yildiz, Takwa Chouki, Aycan Atli, Moussab Harb, Sammy W Verbruggen, Rajeshreddy Ninakanti, Saim Emin, 2021, izvirni znanstveni članek Opis: Developing an efficient material as a counter electrode (CE) with excellent catalytic activity, intrinsic stability, and low cost is essential for the commercial application of dye-sensitized solar cells (DSSCs). Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. Here, we exploited different phases of iron phosphide as CEs in DSSCs with an I–/I3–-based electrolyte. Solvothermal synthesis using a triphenylphosphine precursor as a phosphorus source allows to grow a Fe2P phase at 300 °C and a FeP phase at 350 °C. The obtained iron phosphide catalysts were coated on fluorine-doped tin oxide substrates and heat-treated at 450 °C under an inert gas atmosphere. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96 ± 0.06%, which is comparable to the device assembled with a platinum (Pt) CE. DFT calculations support the experimental observations and explain the fundamental origin behind the improved performance of Fe2P compared to FeP. These results indicate that the Fe2P catalyst exhibits excellent performance along with desired stability to be deployed as an efficient Pt-free alternative in DSSCs.
Ključne besede: Iron phosphide, catalyst, counter electrode, dye-sensitized solar cell, solvothermal synthesis
Objavljeno v RUNG: 06.02.2023; Ogledov: 487; Prenosov: 0
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4. Synthesis and application of transition metal phosphide nanomaterials as electrocatalysts for water splitting and chemical transformations : dissertationTakwa Chouki, 2022, doktorska disertacija Opis: In this thesis, we will focus on the solvothermal synthesis of iron phosphides (FeP, Fe2P) using triphenylphosphine (TPP) as an inexpensive and stable phosphorus source. The obtained iron phosphides were applied as electrocatalysts in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), Rhodamine B (RhB) degradation, Escherichia coli (E. coli) inactivation,
nitrates reduction reaction (NO3RR) to ammonia (NH3), and as counter electrodes in dye-sensitized solar cells (DSSCs). Detailed characterizations of catalysts were carried out to investigate the correlations between the material structure and catalytic activity.
The first part of the thesis gives an introduction to the topic which cover overview of literature about the use of transition metal phosphide as efficient electrocatalysts in water splitting studies, NO3RR to NH3 and DSSCs.
The second part is a description of the experimental methods.
The third part discusses the solvothermal synthesis of FeP and Fe2P catalysts using TPP precursor. The phase conversion of iron phosphides at elevated temperatures under reductive atmosphere was reported. Structural characterizations of the obtained materials were achieved using multiple techniques. The electrocatalytic activities of heat-treated iron phosphide films for HER were studied in acidic environment.
The fourth part discusses the use of Fe2P nanoparticles (NPs) for OER.
The fifth part outlines the use of Fe2P precatalyst in water treatment studies. Using a thin film of Fe2P precatalyst, RhB degradation and E. coli inactivation in the presence of in-situ generated reactive chlorine species were reported. Characterization of Fe2P electrocatalysts before and after the test was carried out using different techniques.
The sixth part shows for the first time the use of FeP and Fe2P as a noble metal-free electrocatalysts for NO3RR to NH3. In this chapter we will emphasize the nitrate reaction pathways, which are highly complex and poorly understood.
The seventh part demonstrates the use of FeP and Fe2P catalysts as robust and efficient counter electrodes in DSSCs.
Ključne besede: solvothermal synthesis, iron phosphides, electrocatalysis, HER, OER, RhB degradation, E. coli inactivation, NO3RR to NH3, DSSCs, dissertations
Objavljeno v RUNG: 29.08.2022; Ogledov: 1053; Prenosov: 84
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7. Cost-effective Green Synthesis of Boron rich Carbide Coatings for IR Windows and Night Vision OpticsSwapna Mohanachandran Nair Sindhu, 2020, izvirni znanstveni članek Opis: The increasing demand for infrared (IR) window materials for various applications in optical imaging systems necessitates the development of cost-effective green techniques. Herein, the synthesis of refractory boron carbide (BC) using castor oil, as carbon precursor, and the preparation of IR transparent films by thermal vapor deposition technique is reported. Films are prepared with 1:3, 1:4, and 1:5 ratios of boric acid and castor oil, respectively. The X-ray diffraction (XRD) and Fourier-transform IR (FTIR) analyses reveal the structure of films prepared to be BC. The morphology of the films is analyzed by the atomic force microscopy (AFM) technique, and its dependence on precursor’s ratio is also studied. The spectroscopic characterization by the ultraviolet–visible–near IR (UV–vis–NIR) transmittance study reveals the potential of the films for IR window applications. The bandgap energy of the BC films determined from the Tauc plot yields a value of 2.33 eV. The absorption coefficient, extinction coefficient, refractive index, dissipation factor, and optical conductivity are also studied from the reflectance and transmittance data.
Ključne besede: Green Synthesis, Boron rich Carbide, coatings, IR Windows
Objavljeno v RUNG: 05.07.2022; Ogledov: 651; Prenosov: 0
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8. Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens studyV. Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek Opis: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports
the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confirm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Ključne besede: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Objavljeno v RUNG: 04.07.2022; Ogledov: 709; Prenosov: 0
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9. Boron carbide Nanowires from castor oil for optronic applications: A low-temperature greener approachSwapna Mohanachandran Nair Sindhu, 2021, izvirni znanstveni članek Opis: The development of one-dimensional nanostructures has revolutionized electronic and photonic industries because of their unique properties. The present paper reports the low-temperature green synthesis of boron carbide nanowires, of diameter 14 nm and length 2 lm, by the condensation method using castor oil as the carbon precursor. The nanowires synthesized exhibit beaded chain morphology, and bandgap energy of 2.08 eV revealed through the Tauc plot analysis. The structure of boron carbide nanowires is revealed by micro-Raman, Fourier transform infrared spectroscopic, and X-ray diffraction analyses. The thermogravimetric analysis of the sample reveals the excellent thermal stability. The photoluminescence study reveals the nanowire’s blue light emission capability under ultraviolet excitation, which is substantiated by the CIE plot suggesting its potential in photonic applications.
Ključne besede: Boron carbide, Nanowires, castor oil, green synthesis
Objavljeno v RUNG: 04.07.2022; Ogledov: 604; Prenosov: 0
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10. Natural precursor based hydrothermal synthesis of sodium carbide for reactor applicationsSwapna Mohanachandran Nair Sindhu, 2017, izvirni znanstveni članek Opis: Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.
Ključne besede: sodium carbide, pandanus, hydrothermal synthesis, porous materials
Objavljeno v RUNG: 30.06.2022; Ogledov: 753; Prenosov: 0
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