Browsing by Author "Partanen, Lauri"

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Ab initio molecular dynamics investigation of the Pt(111)-water interface structure in an alkaline environment with high surface OH-coverages
(2024-07-14) Partanen, Lauri; Laasonen, Kari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, we investigate the structure of the Pt(111)-water interface in an alkaline environment with large OH coverages of 1/3, 2/3 and 1 monolayer using a large well-equilibrated system. We observe that the OH coverage influences both the orientational distribution of the water molecules and their density, with more structure associated with higher coverage. At the same time, there is evidence of a highly dynamic hydrogen bond network on the lower coverage systems with substantial exchange of water between the surface and the solvent. In addition to OH and H2O species, which are preferentially located at the top sites, the 1/3 and 2/3 monolayer surfaces also contain O atoms, which are relatively stable and prefer the hollow sites. In contrast, the 1 monolayer surface shows none of these dynamics, and is unlikely to be active. The dynamic coexistence of O, OH and H2O on Pt(111) electrodes in alkaline conditions necessitates the investigation of several possible reaction paths for processess like ORR and water splitting. Finally, the exchange processes observed between the solvent and the interface underscore the need to explicitly include liquid water in simulations of systems similar to Pt(111).
Ei-elektrolyyttiliuosten aktiivisuuskerroinmallit
(2023-06-07) Mäenpää, Sampsa
Kemiantekniikan korkeakoulu | Bachelor's thesis
How student-centred teaching in quantum chemistry affects students' experiences of learning and motivation - A self-determination theory perspective
(2020-01-16) Partanen, Lauri
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper represents the second contribution from an action research study on a bachelor-level quantum chemistry and spectroscopy course. In the proposed instructional model, active learning principles are extended outside lectures to form a student-centred course structure. The new model resulted in superior learning outcomes compared to a class where active learning elements were limited to course lectures, as demonstrated by previous research. In this article, I try to understand this improvement through an analysis of student motivation and experiences in the framework of self-determination theory. Based on my analysis of student feedback data and interviews, tasks that facilitated direct interaction with peers or course staff were seen as key factors in enhancing learning and motivation. In addition, the presence of various interconnected course components that supported students at different stages of the learning process was experienced as central to learning. Together, these two publications demonstrate that the incorporation of active learning principles outside lectures can substantially improve both learning and motivation.
Hydrogen adsorption trends on two metal-doped Ni2P surfaces for optimal catalyst design
(2021-05-21) Partanen, Lauri; Alberti, Simon; Laasonen, Kari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, we looked at the hydrogen evolution reaction on the doubly doped Ni3P2 terminated Ni2P surface. Two Ni atoms in the first three layers of the Ni2P surface model were exchanged with two transition metal atoms. We limited our investigation to combinations of Al, Co, and Fe based on their individual effectiveness as Ni2P dopants in our previous computational studies. The DFT calculated hydrogen adsorption free energy was employed as a predictor of the materials' catalytic HER activity. Our results indicate that the combination of Co and Fe dopants most improves the catalytic activity of the surface through the creation of multiple novel and active catalytic sites.
Hydrogen adsorption trends on various metal-doped Ni2P surfaces for optimal catalyst design
(2019-01-01) Partanen, Lauri; Hakala, Mikko; Laasonen, Kari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, we looked at the hydrogen evolution reaction on Mg-, Mo-, Fe-, Co-, V-, and Cu-doped Ni3P2 and Ni3P2 + P terminated Ni2P surfaces. The DFT calculated hydrogen adsorption free energy was employed as a predictor of the materials' catalytic HER activity. Our results indicate that doping can substantially improve the catalytic activity of the Ni3P2 terminated surface. In contrast, the Ni3P2 + P terminated one seems to be catalytically active irrespective of the type of doping, including in the absence of doping. Based on our doping energy and adsorption free energy calculations, the most promising dopants are iron and cobalt, whereas copper is less likely to function well as a doping element.
Oxygen Evolution Reaction Kinetic Barriers on Nitrogen-Doped Carbon Nanotubes
(2018-06-01) Partanen, Lauri; Murdachaew, Garold; Laasonen, Kari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We investigate kinetic barriers for the oxygen evolution reaction (OER) on singly and doubly nitrogen-doped single-walled carbon nanotubes (NCNTs) using the climbing image nudged elastic band method with solvent effects represented by a 45-water-molecule droplet. The studied sites were chosen based on a previous study of the same systems utilizing a thermodynamic model which ignored both solvent effects and kinetic barriers. According to that model, the two studied sites, one on a singly nitrogen-doped CNT and the other on a doubly doped CNT, were approximately equally suitable for OER. For the four-step OER process, however, our reaction barrier calculations showed a clear difference in the rate-determining *OOH formation step between the two systems, with barrier heights differing by more than 0.4 eV. Thus, the simple thermodynamic model may alone be insufficient for identifying optimal OER sites. Of the remaining three reaction steps, the two H2O forming ones were found to be barrierless in all cases. We also performed solvent-free barrier calculations on NCNTs and undoped CNTs. Substantial differences were observed in the energies of the intermediates when the solvent was present. In general, the observed low activation energy barriers for these reactions corroborate both experimental and theoretical findings of the utility of NCNTs for OER catalysis.
Student-centred active learning approaches to teaching quantum chemistry and spectroscopy: Quantitative results from a two-year action research study
(2018-01-01) Partanen, Lauri
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this article, I propose a student-centred approach to teaching quantum chemistry and spectroscopy at the bachelor-level that extends active learning principles outside course lectures. The aim is to elucidate what type of methodology is most appropriate and efficient for this context and student population, and how this incorporation of active learning elements impacts learning. Three quantitative learning indicators are used to measure the effectiveness of the proposed approach, including exercise points obtained by the students, exam results, and the results of a conceptual inventory administered both at the beginning and the end of the course. The proposed model resulted in substantial improvement in learning outcomes compared to a previous class where active learning elements were confined mostly to the course lectures and a traditionally taught class. The model can be generalised to any subject where both quantitative and qualitative understanding is required. Thus, in addition to providing further support for the effectiveness of active learning approaches in science, this study shows the benefits of applying these approaches to exercises and other course tasks besides lectures.
Vedyn kehittymisreaktion mekanismit emäksisissä olosuhteissa
(2024-09-05) Sundman, Sofia
Kemiantekniikan korkeakoulu | Bachelor's thesis
Vedyn kehittymisreaktiossa vetyä tuotetaan vedestä sähkökemiallisesti, jonka jälkeen energia varastoidaan ja uudelleen käytetään. Vedyn kehittymisreaktio emäksisissä olosuhteissa voi tapahtua joko Volmer-Heyrovsky – tai Volmer-Tafel reaktioiden kautta. Reaktion Volmer- vaiheessa vesimolekyylit pelkistyvät atomivedyksi. Tämän jälkeen reaktiossa muodostuu vetymolekyylejä. Reaktio voi olla joko sähkökemiallinen Heyrovsky-reaktio, jossa atomivedyn ja elektronin yhdistelmästä saadaan vetymolekyylejä, tai kemiallinen Tafel-reaktio, jossa kaksi vetyatomia yhdistyy muodostaen vetymolekyyljejä. Vedyn kehittymisreaktiossa emäksisissä olosuhteissa tarvitaan tehokkaita elektrokatalyyttejä, joiden haluttuja ominaisuuksia ovat aktiivisuus, selektiivisyys, kestävyys sekä helppo saatavuus. Yhden atomin katalyyteissä (single atom catalyst, SAC) funktionaaliset atomit ovat erillään toisistaan. Näillä katalyyteillä on suuri muokattavuus ja pinta-ala-suhde. Siirtymämetallikatalyytit puolestaan herättävät kiinnostusta vedyn kehittymisreaktiossa niiden helpon saatavuuden ja korkean aktiivisuuden vuoksi. Lisäksi vedyn kehittymisreaktiossa emäksisissä olosuhteissa on tutkittu laajasti tuotannossa jo valmiiksi käytettävää fullereeniyhdistettä ja sen yhdistämistä platinaklustereihin. Vedyn kehittymisreaktiolla on keskeinen rooli tulevaisuuden vetyteknologiassa ja kestävän energian tuotannossa. Vetyä pidetään ympäristöystävällisenä ja kestävänä energianlähteenä, jolla on mahdollisuus tulevaisuudessa kilpailla fossiilisten polttoaineiden kanssa. Tulevaisuuden haasteita vedyn kehittymisreaktiossa käytettävissä katalyyteissä ovat yhä kestävämpien ja ympäristöystävällisempien materiaalien hyödyntäminen katalyyteissä. Lisäksi vedyn kehittymisreaktion mekanismeista emäksisissä olosuhteissa tarvitaan lisää ymmärrystä , jotta katalyyttejä voidaan optimoida reaktion nopeuttamiseksi.