Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 2 / 2
First pagePrevious page1Next pageLast page
1.
Performance of copper - based catalysts for electrochemical CO2 reduction
Stefan Popović, 2023, doctoral dissertation

Abstract: The industrial era has brought a never-ending problem to civilization through the emission of greenhouse gases (GHGs) while extracting energy from fossil fuels for a variety of processes. Among different GHGs, carbon dioxide (CO2) stood out as one of the most impactful and dangerous gases causing climatic disasters around the globe. However, CO2 as the abundant C1 building block, through the conversion pathways gives a plethora of opportunities to convert it into a wide range of commercial products and applications. The holistic approach among different conversion pathways is the electrochemical reduction of CO2 (eCO2R), ideally powered by renewable energy from intermittent sources such as wind and solar power. A silver bullet of the process is to find a catalyst that is active, selective, and stable. Copper has been recognized as the only monometallic catalyst that can produce products that require a transfer of >2e-. However, in recent years the increased awareness of its reconstructive nature under eCO2RR-relevant conditions multiplied the complexity of the parameters that can influence the reaction. Therefore overall thesis's approach to studying copper-based catalysts is based to understand the reconstructive aspect and the stability of Cu-based catalysts, and deeply comprehend their relationship with the activity/selectivity. Chapter 1 gives an introduction to the recent activities in the field of carbon capture, utilization and storage (CCSU) technologies, the fundaments of CO2 as a molecule, and its pathway toward state-of-the-art discoveries in the eCO2 R reaction. Afterward, the thesis focuses on the main experimental technique to produce nanostructured copper-based materials, namely, electrodeposition (Chapter 2). A big part of the thesis focuses on the establishment of an electrochemical setup for activity/selectivity measu rement. The setup consists of two parts: 1) construction of the custom-made gas-tight sandwich-type electrochemical cell and 2) optimization of the online gas and ex-situ liquid product detection. After the establishment of the reliable electrochemical setup, Chapter 3 focuses on electrochemically -grown Cu2O nanocubes catalyst and how the reconstructive nature induced by a particular electrochemical protocol influences on boost in activity/selectivity for methane production. The last part of the thesis consists contribution to the fundamental understanding of the degradation mechanisms and stability of Cu -based catalysts under eCO2RR conditions. A unique ex-situ approach, mirrored in identical location scanning electron microscopy (IL-SEM) method is employed to study electrodeposited spherical half-micron particles on the glassy carbon rotating disk electrode (GC-RDE). With this evidence, we could interpret the observed structural changes as two separate electrochemical processes occurring one after another, namely copper dissolution from pre-oxidized native nanoparticles and subsequent (electro -) redeposition of the dissolved copper species in a form of n ew smaller Cu fragments.
Keywords: electrocatalysts, electrochemical CO2 reduction, copper nanoparticles, IL-SEM, stability, degradation
Published in RUNG: 14.11.2023; Views: 951; Downloads: 16
.pdf Full text (5,55 MB)

2.
Highly active iron phosphide catalysts for selective electrochemical nitrate reduction to ammonia
Takwa Chouki, Manel Machreki, Iwona A. Rutkowska, Beata Rytelewska, Pawel Jozef Kulesza, Georgi Tyuliev, Moussab Harb, Luis Miguel Azofra, Saim Emin, 2023, original scientific article

Abstract: The electrochemical reduction reaction of the nitrate ion (NO3−), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach for environmental remediation and green energy conservation. The development of high-performance electrocatalysts to selectively reduce NO3− wastes into value-added NH3 will open up a different route of NO3− treatment, and impose both environmental and economic impacts on sustainable NH3 synthesis. Transition metal phosphides represent one of the most promising earth-abundant catalysts with impressive electrocatalytic activities. Herein, we report for the first time the electrocatalytic reduction of NO3− using different phases of iron phosphide. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product was achieved using 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). The recycling tests confirmed that Fe2P and FeP catalysts exhibit excellent stability during the NO3− reduction at − 0.37 V vs. 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. These results indicate that the Fe2P phase exhibits excellent performance to be deployed as an efficient noble metal-free catalyst for NH3 generation.
Keywords: iron phosphide, electrocatalysts, nitrates reduction ammonia, DFT calculations
Published in RUNG: 02.02.2023; Views: 1408; Downloads: 4
.pdf Full text (7,95 MB)
This document has many files! More...

Search done in 0.01 sec.
Back to top