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1.
Materials for sustainable electrochemical energy conversion
Saim Emin, Takwa Chouki, Manel Machreki, 2023, published scientific conference contribution abstract (invited lecture)

Abstract: The process of hydrogen evolution reaction (HER) through water electrolysis is an important technology for establishing the so called "hydrogen economy". Here we will cover different systems for electrocatalytic HER. Transition metal carbides and metal phosphides are alternative to platinum (Pt) and offer excellent electrocatalytic activity for HER. Pyrolysis of hexacarbonyl tungsten, W(CO)6, in 1-octadecene has been used to prepare colloidal tungsten, W, nanoparticles (NPs) [1]. The obtained W NPs has been spin-coated on graphite (C) electrodes. Heat treatment of the W/C electrodes at elevated temperatures (≥ 900°C) allows the preparation of metallic W and tungsten carbide (W2C@WC) thin films. The obtained W2C@WC electrodes were used for hydrogen evolution studies (HER) in 0.5M H2SO4. Cyclic voltammetry tests for 1000 cycles showed that W2C@WC exhibit long term stability without significant drop in current density. The overpotential defined at 10 mA/cm2 is 310 mV vs. RHE giving an excellent catalytic activity for HER. Iron phosphide electrocatalysts were synthesized using a triphenylphosphine (TPP) precursor. Different iron phosphide phases were synthesized at 300°C (Fe2P) and at 350°C ( FeP ) [2]. To enhance the catalytic activities of obtained iron phosphide particles heat-treatments were carried out at elevated temperatures. Annealing at 500°C under reductive atmosphere 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 lowest electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with Fe2P/FeP−500°C catalyst
Keywords: Fe2P, electrocatalysis, hydrogen, ammonia
Published in RUNG: 13.12.2023; Views: 864; Downloads: 3
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2.
Tuning the activity of iron phosphide electrocatalysts for sustainable energy conversion
Saim Emin, Takwa Chouki, Manel Machreki, 2023, published scientific conference contribution abstract (invited lecture)

Abstract: Electrocatalysis is a promising approach for the sustainable conversion of renewable energy sources, such as solar and wind power, into chemical energy that can be stored and used on demand. By harnessing renewable electricity to drive electrochemical reactions, we can produce fuels and chemicals in a way that is both clean and cost-effective. As we continue to develop new electrocatalytic materials and improve the efficiency of existing processes, the potential for electrocatalysis to transform our energy system will only continue to grow. We report the use of iron phosphide (Fe2P, FeP) in several electrocatalytic applications, such as reduction of nitrate ions (NO3), hydrogen and oxygen evolution studies. The electrochemical reduction of the nitrate ion (NO3), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach to achieving green energy conservation. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product using a bi-potentiostat was achieved by electrooxidation of NH3 to nitrogen (N2) on a Pt electrode. The Fe2P catalyst exhibits the highest Faradaic efficiency (96%) for NH3 generation with a yield (0.25 mmol h−1 cm-−2 or 2.10 mg h−1 cm−2) at −0.55 V vs. reversible hydrogen electrode (RHE). To get relevant information about the reaction mechanisms and the fundamental origins behind the better performance of Fe2P, density functional theory (DFT) calculations were performed.
Keywords: Fe2P, FeP, electrocatalysis, NH3 reduction, counter electrode
Published in RUNG: 04.12.2023; Views: 772; Downloads: 4
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3.
Electrocatalytic hydrogen evolution with textured iron phosphides thin films
Saim Emin, 2019, published scientific conference contribution abstract

Abstract: We used wet-chemistry techniques to prepare colloidal iron phosphides (F2P) nanoparticles (NPs). The synthesis of Fe2P NPs was conducted using the so called hot-matrix method [1]. The sizes of obtained Fe2P NPs are in the order of 2 - 5 nm. The colloidal Fe2P NPs are coated with hydrophobic molecules which allow preparation of stable dispersion in organic solvents like choloroform (CHCl3). The colloidal F2P NPs are very suitable for the preparation of thin films via spin-coated, spray coated or inkjet-printed on various conductive substrates. The obtained Fe2P films were used in hydrogen evolution reaction (HER). In addition, to HER the Fe2P films were used for electrocatalytic degradation of organics.
Keywords: Fe2P, electroctalysis, thin films
Published in RUNG: 13.05.2021; Views: 2577; Downloads: 0
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