Kuno Kooser

In this work, we propose hydroxyapatite (HA) as a hard template to unlock the porosity of Fe–N–C catalyst materials. Using HA, a naturally occurring mineral that can be removed with nitric acid, in the synthesis generates a catalyst material with a unique porous network comprising abundant pores and interparticle cavities ranging from 10 to 3000 nm. Hard templating with HA alongside ZnCl2 as a micropore former results in a Fe–N–C catalyst based on naturally abundant peat with excellent oxygen reduction activity in alkaline conditions. A half-wave potential of 0.87 V vs RHE and a peak power density of 1.06 W cm−2 were achieved in rotating ring disk electrode and anion exchange membrane fuel cell experiments, respectively, rivaling the performance of other state-of-the-art platinum-free catalysts presented in the literature. A combined approach of using renewable peat as a carbon source and HA as a hard …

Radiation therapy uses ionizing radiation to break chemical bonds in cancer cells, thereby causing DNA damage and leading to cell death. The therapeutic effectiveness can be further increased by making the tumor cells more sensitive to radiation. Here, we investigate the role of the initial halogen atom core hole on the photofragmentation dynamics of 2-bromo-5-iodo-4-nitroimidazole, a potential bifunctional radiosensitizer. Bromine and iodine atoms were included in the molecule to increase the photoionization cross-section of the radiosensitizer at higher photon energies. The fragmentation dynamics of the molecule was studied experimentally in the gas phase using photoelectron-photoion-photoion coincidence spectroscopy and computationally using Born-Oppenheimer molecular dynamics. We observed significant changes between shallow core (I 4d, Br 3d) and deep core (I 3d) ionization in fragment …

Photodissociation molecular dynamics of gas-phase 2,5-diiodothiophene molecules was studied in an electron-energy-resolved electron-multi-ion coincidence experiment performed at the FinEstBeAMS beamline of MAX IV synchrotron. Following the photoionization of the iodine 4d subshell and the Auger decay, the dissociation landscape of the molecular dication was investigated as a function of the Auger electron energy. Concentrating on an major dissociation pathway, C4H2I2S2+ → C4H2S+ + I+ + I, and accessing the timescales of the process via ion momentum correlation analysis, it was revealed how this three-body process changes depending on the available internal energy. Using a generalized secondary dissociation model, the process was shown to evolve from secondary dissociation regime towards concerted dissociation as the available energy increased, with the secondary dissociation time …

In this work thin film SOFC anode MIEC La 0.31 Sr 0.58 Ti 0.97 Ni 0.03 O 3-δ (LSTN) electrodes with embedded 200 nm thick Pt current collectrors (CC-s) and electrodes without CC-s deposited on 10Sc1CeSZ electrolyte were studied in 650 C in 98.5% H 2 and 1.5% H 2 O at ambient pressure. Additionally Pt-10Sc1CeSZ electrodes were characterized to determine CC-s own electrochemical activity. It was found that the embedded Pt was the most active part of an LSTN electrode with Pt CC despite the common presumption that covering Pt current collector with dense MIEC layer makes it inactive. Diffusion of H 2 through both LSTN and Pt layers and reaction on the Pt-10Sc1CeSZ interface is proposed. Formation of bubbles under embedded Pt in hydrogen atmosphere was seen and is explained with formation of trapped H 2 O.

To improve catalytic activity of La x Sr 0.9-x Ti y M 1-y O 3-δ, La 1-x Sr x Cr y M 1-y O 3-δ based materials, doping of perovskite B-site with metals (M) like Ni, Co, Mo or Cu has been proposed. It has been demonstrated, that at elevated temperatures and in reducing atmosphere these dopants exsolve to perovskite surface and form nanometer scale catalyst particles. Exsolution process could be accelerated by using electrochemical polarization. In the present study thin film La 0.31 Sr 0.58 Ti 0.97 Ni 0.03 O 3-δ electrodes was prepared using pulsed laser deposition (PLD) technique. Current collectors were made from Pt (using magnetron sputtering) and placed under the thin film electrode layer. Electrodes were characterized using XPS and EIS method at near ambient pressure conditions (1-5 mbar) at 650 C, activated electrochemically and characterized again to see the effect of activation. Changes on the …

To make solid oxide fuel cell (SOFC) systems commercially attractive it's essential to reduce manufacturing cost and improve the stability of membrane electrode assembly (MEA). In this research, the influence of A-site modification on electrical and electrochemical performance of 5% A-site deficient La 0.21 Sr 0.74− x Ca x Ti 0.95 Fe 0.05 O 3− δ (x= 0.26− 0.69)(LSCTF5-x) hydrogen electrode has been studied. Results indicate that the magnitude of A-site deficiency and Ca concentration in A-site influence the conductivity, catalytic activity and stability of the electrodes considerably. The highest stability was observed in the case of La 0.21 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3− δ anode composition. The maximal total electrical conductivity of porous electrode layer made of LSCFT5-x was 3.5 S cm− 1 at 850 C characteristic of the La 0.211 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3− δ material in 97% H 2+ 3% H 2 O …

Heavy elements and some nitroimidazoles both exhibit radiosensitizing properties through different mechanisms. In an effort to see how the overall radiosensitivity might be affected when the two radiosensitizers are combined in the same molecule, we studied the gas-phase photodissociation of two brominated nitroimidazoles and a bromine-free reference sample. Synchrotron radiation was employed to initiate the photodynamics and energy-resolved multiparticle coincidence spectroscopy was used to study the ensuing dissociation. We observed the brominated samples releasing high amounts of potentially radiosensitizing fragments upon dissociation. Since bromination also increases the likelihood of the drug molecule being ionised per a given X-ray dose, we conclude that heavy-element substitution of nitroimidazoles appears to be a viable path towards new, potent radiosensitizer drugs.

Development of active ceramic hydrogen electrodes with high stability is an important challenge for developing solid oxide fuel cells (SOFC). Herein, a set of cubic perovskite-type La/Ca/Fe-doped strontium titanates, La0.2Sr0.7–xCaxTi0.95Fe0.05O3-δ (LSCTF), was synthesized. Their crystallographic and electrical properties, catalytic activity, and stability, as well as performance as fuel electrodes in the solid oxide fuel cell (SOFC) have been evaluated. It was confirmed by the results that the LSCTF behave like semiconductors, and the conductivity, catalytic activity, and stability of the electrodes significantly depend on the Ca concentration in the A-site. In the case of an optimal composition of the La0.2Sr0.35Ca0.35Ti0.95Fe0.05O3−δ fuel electrode, a polarization resistance value of 0.21 Ω cm2 at 850 °C in a humidified (1.7% H2O) H2 atmosphere was obtained. During the stability test, the fuel cell with the 50 wt …

In this progress report, we show the results of two mass spectrometric experiments performed on a set of nitroimidazole-based radiosensitizers, medications that enhance radiation damage to the cancerous cells (Itälä et al. 2019 and 2020, Rockwell et al. 2009). We have incorporated a heavy element (Br and/or I) into the structure to introduce an additional function to the radiosensitizer. The idea here is that heavy element absorption hotspot locally enhances the radiation dose by generating secondary X-rays, photo-and Auger electrons, while the other part of the molecule produces sensitization-relevant species upon fragmentation (radicals originating from nitro group). Potentially it could increase the positive outcome from the radiation therapy, minimizing negative effects on normal cells. It is often difficult to interpret the results of clinical trials in the context of fundamental physical and chemical processes …

(La 0.6 Sr 0.4) 0.99 CoO 3− δ is a very promising cathode material due to its excellent electronic and ionic conductivity. However, non-artificial air from the ambient atmosphere contains impurities such as H 2 O and CO 2, which cause degradation and performance loss of the cathode. Introduction of Ti into the B-site of (La 0.6 Sr 0.4) 0.99 CoO 3− δ improves the chemical stability of the material.(La 0.6 Sr 0.4) 0.99 Co 1− x Ti x O 3− δ (0≤ x≥ 0.1) electrodes prepared in this work were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Studied (La 0.6 Sr 0.4) 0.99 CoO 3− δ materials with Ti in B-site showed reversible degradation under gas mixture with carbon dioxide addition. Improved stability was observed for (La 0.6 Sr 0.4) 0.99 Co 1− x Ti x O 3− δ materials with Ti in B-site compared to unmodified (La 0.6 Sr 0.4) 0.99 CoO 3 …

(La0. 6Sr0. 4) 0.99CoO3− δ oxygen electrode material is a very promising oxygen electrode material due to its excellent electron and ionic conductivity. However, when using non-artificial air from the ambient atmosphere, it contains impurities such as H2O and CO2. These chemicals increase the degradation rate of the oxygen electrode. Introducing Ti into the B-site of (La0. 6Sr0. 4) 0.99CoO3− δ B-site increases the chemical stability of this oxygen electrode material. Synthesized and fabricated (La0. 6Sr0. 4) 0.99Co1− xTixO3− δ (0≤ x≥ 0.1) electrodes and half cells were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and with electrochemical impedance spectroscopy (EIS). Results indicate that doping of (La0. 6Sr0. 4) 0.99CoO3− δ B-site with Ti makes this material more resilient to form unwanted compounds on the oxygen electrode surface.

In this work, we studied the effects of Ni-doping level on the catalytic activity, stability and mobility of A-site cations of the La0.25Sr0.25Ca0.4TiO3−δ (LSCT) fuel electrode. Results indicate that Ni concentration in B-site influences the phase properties, element ratios on the surface, element mobility during preparation, conductive properties and catalytic activity of electrode significantly. The best performance was measured for La0.25Sr0.25Ca0.4Ti0.95Ni0.05O3−δ having very low polarization resistance value 0.084 Ω cm2 at 850 °C (at OCV). The results of the experiments indicate excellent stability of the material – Rp remained stable during the 120 h test. Ni-doping also stabilizes the LSCT structure and makes it more stable in different gas atmospheres and suppresses segregation of CaO to the electrode surface. Moreover, it even suppresses significantly A-site cation mobility during electrode processing, which …

The Highly Oxidized Molecule Ion Spectrometer (HOMIS) is a novel instrument for measuring the total concentration of highly oxidized molecules (HOM-s)(Bianchi et al., 2019) at atmospheric pressure. The device combines a chemical ionization charger with a multi-channel differential mobility analyzer. The chemical ionization charger is based on the principles outlined by Eisele and Tanner (1993). The charger is attached to a parallel differential mobility analyzer identical to the ones used in the Neutral cluster and Air Ion Spectrometer (NAIS, Mirme 2011), but with modified sample and sheath air flow rates to improve the mobility resolution of the device. The complete mobility distribution in the range from 3.2 to 0.056 cm2/V/s is measured simultaneously by 25 electrometers. The range captures the charger ions, monomers, dimers, trimers but also extends far towards larger particles to possibly detect larger HOM-s …

Absorption of x-ray photons by atomic inner shells of light-element organics and biomolecules often leads to formation of dicationic electronic states and to molecular fragmentation. We investigated the x-ray-induced dissociation landscape of a representative medium-sized organic molecule, thiophene, by femtosecond x-ray pulses from the Super Photon Ring-8 GeV (SPring-8) Angstrom Compact Free-Electron Laser (SACLA). Holes, created in the sulfur 2 p orbital by photoemission, were filled by the Auger process that created dicationic molecular states within a broad range of internal energies—a starting point particular to x-ray-induced dynamics. The evolution of the ionized molecules was monitored by a pump-probe experiment using a near-infrared (800 nm) laser pulse. Ion-ion coincidence and ion momentum analysis reveals enhanced yields of ionic fragments from multibody breakup of the ring, attributed to …

We studied the gas-phase photodissociation of a fully halogenated aromatic molecule, tetrabromothiophene, upon core–shell ionization by using synchrotron radiation and energy-resolved multiparticle coincidence spectroscopy. Photodynamics was initiated by the selective soft X-ray ionization of three elements – C, S, and Br – leading to the formation of dicationic states by Auger decay. From a detailed study of photodissociation upon Br 3d ionization, we formulate a general fragmentation scheme, where dissociation into neutral fragments and a pair of cations prevails, but dicationic species are also produced. We conclude that dicationic tetrabromothiophene typically undergoes deferred charge separation (with one of the ions being often Br+) that may be followed by secondary dissociation steps, depending on the available internal energy of the parent dication. Observations suggest that the ejection of neutral …

The search for alternative fuel electrode materials to Ni-cermets is very active in the solid oxide cell (SOC) field due to several reasons. Metallic Ni is very sensitive to oxygen partial pressure (p O2) and reoxidizes to NiO if p O2 rises above the threshold level (temperature dependent). Ni-cermets are also prone to sulphur poisoning 1,2 and coking 3 if carbonaceous fuel without sufficient steam is used. Even if gases are carefully purified from sulphur, and correct steam to carbon ratio is used, metallic Ni centres still has a tendency to coarsen over time, which leads to performance losses 4,5.Full ceramic anodes are envisaged as redox stable materials when compared to metal-cermets – there is no immense expansion relating to metal oxidation reduction cycles and these materials are more resistant to coking and sulphur depositions 6–8. La0.2Sr0.7 - xCaxTiO3 …

The electrochemical and crystalline structure of mixed ionic‐electronic conductive La0.75Sr0.25Cr0.5Mn0.3Ni0.2O3–δ (LSCMN) electrode in porous scandia ceria stabilized zirconia (ScCeSZ) electrolyte matrix during the first 140 h has been studied in an operando XRD experiment. Intense degradation of electrochemical performance in a fuel cell as well as in electrolysis modes has been observed. However, the mechanism of the degradation was seen to be different for the two operation modes. The formation of the new ceramic phase was observed on the surface of the electrode using the Grazing incidence X‐ray diffraction at the pulsed laser deposited LSCMN model electrode. Instability of the LSCMN phase in the ScCeSZ matrix at SOFC working conditions has been demonstrated using the novel operando XRD technique. The decrease in wt.% of the LSCMN during degradation was approximately 27 ± 4 …

In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film N i− C e 0.9 G d 0.1 O 2− δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H 2 pressures and at different electrochemical conditions at around 650° C. The possible redox reactions on the anode surface (N i 2+↔ N i 0, C e 4+↔ C e 3+) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the C e 3 d and N i 2 p photoelectron spectra caused by electrode potential and H 2 pressure variations were observed and …

Since spring 2019 an experimental setup consisting of an electron spectrometer and an ion time-of-flight mass spectrometer for diluted samples has been available for users at the FinEstBeAMS beamline of the MAX IV Laboratory in Lund, Sweden. The setup enables users to study the interaction of atoms, molecules, (molecular) microclusters and nanoparticles with short-wavelength (vacuum ultraviolet and X-ray) synchrotron radiation and to follow the electron and nuclear dynamics induced by this interaction. Test measurements of N2 and thiophene (C4H4S) molecules have demonstrated that the setup can be used for many-particle coincidence spectroscopy. The measurements of the Ar 3p photoelectron spectra by linear horizontal and vertical polarization show that angle-resolved experiments can also be performed. The possibility to compare the electron spectroscopic results of diluted samples with solid …

Thiophene is a cyclic molecule that becomes unstable as a molecular dication. We followed the multi-step dissociation dynamics triggered by soft x-ray FEL pulses from SACLA, core-ionizing the S 2p orbital and creating parent dications by the Auger decay. The time-evolution was probed by optical laser pulsesthat reveal the survival lifetime of the parent dication and the build-up of fragmentation proceeding by ring opening and rupture, accompanied by hydrogen ejection and secondary dissociation. Experimental results are compared to statistical analysis of molecular dynamics simulations.