Browsing by Author "Lund, P. D."

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    3 kWp grid-connected PV-system : annual report 1990
    (1991) Peippo, K.; Lund, P. D.; Teknillisen fysiikan laitos.; Teknillinen korkeakoulu; Helsinki University of Technology
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    Application of dye-sensitized and perovskite solar cells on flexible substrates
    (Institute of Physics Publishing, 2018-03-30) Lund, P. D.; Halme, J.; Hashmi, G.; Asghar, I.; Miettunen, K.; Department of Applied Physics; New Energy Technologies; Aalto University
    In this paper, a review of applying dye-sensitized (DSCs) and perovskite solar cells (PSCs) on flexible substrates is presented. Metallic and polymeric materials are the most common flexible substrates used. Cell integration into a textile substrate is also considered here as a future alternative. Common challenges with these include penetration of humidity, cell stability, and lifetime. Flexible DSCs and PSCs are still a niche technology, but have an inherent potential for cheap roll-to-roll mass production of photovoltaics.
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    Carbonate dual-phase improves the performance of single-layer fuel cell made from mixed ionic and semiconductor composite
    (BioMed Central, 2020-12) Jouttijärvi, S.; Yao, X.; Asghar, M. I.; Etula, J.; Reinecke, A.-M.; Lippmann, W.; Lund, P. D.; Department of Applied Physics; Department of Chemistry and Materials Science; New Energy Technologies; Physical Characteristics of Surfaces and Interfaces; Technical University of Dresden
    A mixed ionic and semiconducting composite in a single-layer configuration has been shown to work as a fuel cell at a lower temperature (500–600 °C) than a traditional solid-oxide fuel cell. The performance of a single-layer fuel cell (SLFC) is often limited by high resistive losses. Here, a eutectic mixture of alkali-carbonates was added to SLFC to improve the ionic conductivity. The dual-phase composite ionic conductor consisted of a ternary carbonate (sodium lithium potassium carbonate, NLKC) mixed with gadolinium-doped cerium oxide (GDC). Lithium nickel zinc oxide (LNZ) was used as the semiconducting material. The LNZ-GDC-NLKC SLFC reached a high power density, 582 mW/cm2 (conductivity 0.22 S/cm) at 600 °C, which is 30 times better than without the carbonate. The best results were obtained with the ternary carbonate which decreased the ohmic losses of the cell by more than 95%, whereas the SLFC with a binary carbonate (sodium lithium carbonate, NLC) showed a lower conductivity and performance (243 mW/cm2, 0.17 S/cm at 600 °C). It is concluded that adding carbonates to LNZ-GDC will improve the ionic conductivity and positively contribute to the cell performance. These results suggest a potential path for further development of SLFCs, but also imply the need for efforts on up-scaling and stability to produce practical applications with SLFC.
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    Device stability of perovskite solar cells – A review
    (2017-09-01) Asghar, M. I.; Zhang, J.; Wang, H.; Lund, P. D.; Department of Applied Physics; New Energy Technologies
    This work provides a thorough overview of state of the art of stability of perovskite solar cells (PSCs) and covers important degradation issues involved in this technology. Degradation factors, which are reported in the literature affecting the stability of PSCs, are discussed. Several degradation mechanisms resulting from thermal and chemical instabilities, phase transformations, exposure to visible and UV light, moisture and oxygen and most importantly sealing issues are thoroughly analyzed. Methods are suggested to study most of these degradation mechanisms in a systematic way. In addition, environmental assessment of PSCs is briefly covered. Alternative materials and their preparation methods are screened with respect to stability of the device. Overall, this work contributes in developing better understanding of the degradation mechanisms and help in improving overall stability of the PSCs.
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    High performance ceramic nanocomposite fuel cells utilizing LiNiCuZn-oxide anode based on slurry method
    (2018-07) Asghar, M. I.; Jouttijärvi, S.; Lund, P. D.; New Energy Technologies; Department of Applied Physics
    A multi-oxide material LiNiCuZn-oxide was prepared through a slurry method as an anode for ceramic nanocomposite fuel cell (CNFC). The CNFCs using this anode material, LSCF as cathode material and a composite electrolyte consisting of CaSm co-doped CeO2 and (NaLiK)2CO3 produced ∼1.03 W/cm2 at 550 °C due to efficient reaction kinetics at the electrodes and high ionic transport in the nanocomposite electrolyte. The electrochemical impedance spectroscopy revealed low ionic transport losses (0.238 Ω cm2) and low polarization losses (0.124 Ω cm2) at the electrodes. The SEM measurements revealed the porous microstructures of the composite materials at electrode and the dense mixture of CaSm co-doped CeO2 and (NaLiK)2CO3. The Brunauer-Emmett-Teller (BET) analysis revealed high surface areas, 4.1 m2/g and 3.8 m2/g, of the anode and cathode respectively. This study provides a promising material for high performance CNFCs.
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    Scalability and feasibility of photoelectrochemical H2 evolution: the ultimate limit of Pt nanoparticle as an HER catalyst
    (Royal Society of Chemistry (RSC), 2015) Kemppainen, E.; Bodin, A.; Sebok, B.; Pedersen, T.; Seger, B.; Mei, B.; Bae, D.; Vesborg, P. C. K.; Halme, J.; Hansen, O.; Lund, P. D.; Chorkendorff, I.; Teknillisen fysiikan laitos; Department of Applied Physics; New Energy Technologies (Renewable); Perustieteiden korkeakoulu; School of Science
    The recent surge in investigating electrocatalysts for the H2 evolution reaction is based on finding a cheap alternative to Pt. However platinum's excellent catalytic activity means very little catalyst needs to be used. The present study combines model experiments with numerical modeling to determine exactly how little catalyst is needed. Specifically we investigate ultra-low Pt loadings for use in photoelectrochemical H2 evolution using TiO2–Ti-pn+Si photocathodes. At a current density of 10 mA cm−2, we photocathodically evolve H2 at +465, +450, +350 and +270 mV vs., RHE at Pt loadings of 1000, 200, 50, and 10 ng cm−2 corresponding to HER overpotentials of η1000ng = 32 mV, η200ng = 46 mV, η50ng = 142 mV, and η10ng = 231 mV. To put this in perspective, if 30% of the world's current annual Pt production was used for H2 evolution catalysis, using a loading of 100 ng cm−2 and a current of 10 mA cm−2 would produce 1 TWaverage of H2. The photoelectrochemical data matched the modeling calculations implying that we were near the fundamental maximum in performance for our system. Furthermore modeling indicated that the overpotentials were dominated by mass transfer effects, rather than catalysis unless catalyst loadings were less than 1000 ng cm−2.