Structural transformations and adsorption properties of PtNi nanoalloy thin film electrocatalysts prepared by magnetron co-sputtering

This is the final peer-reviewed manuscript accepted for publication in Electrochimica Acta Citation of the published version is: Electrochimica Acta 251, 427–441 (2017

Norbornadiene photoswitches anchored to well-defined oxide surfaces: From ultrahigh vacuum into the liquid and the electrochemical environment

Employing molecular photoswitches, we can combine solar energy conversion, storage, and release in an extremely simple single molecule system. In order to release the stored energy as electricity, the photoswitch has to interact with a semiconducting electrode surface. In this work, we explore a solar-energy-storing model system, consisting of a molecular photoswitch anchored to an atomically defined oxide surface in a liquid electrolyte and under potential control. Previously, this model system has been proven to be operational under ultrahigh vacuum (UHV) conditions. We used the tailor-made norbornadiene derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD) and characterized its photochemical and electrochemical properties in an organic electrolyte. Next, we assembled a monolayer of CNBD on a well-ordered Co3O4(111) surface by physical vapor deposition in UHV. This model interface was then transferred into the liquid electrolyte and investigated by photoelectrochemical infrared reflection absorption spectroscopy experiments. We demonstrate that the anchored monolayer of CNBD can be converted photochemically to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC) under potential control. However, the reconversion potential of anchored CQC overlaps with the oxidation and decomposition potential of CNBD, which limits the electrochemically triggered reconversion

Towards an efficient liquid organic hydrogen carrier fuel cell concept

The high temperature required for hydrogen release from Liquid Organic Hydrogen Carrier (LOHC) systems has been considered in the past as the main drawback of this otherwise highly attractive and fully infrastructure-compatible form of chemical hydrogen storage. According to the state-of-the art, the production of electrical energy from LOHC-bound hydrogen, e.g. from perhydro-dibenzyltoluene (H18DBT), requires provision of the dehydrogenation enthalpy (e.g. 65 kJ mol-1(H2) for H18-DBT) at a temperature level of 300 °C followed by purification of the released hydrogen for subsequent fuel cell operation. Here, we demonstrate that a combination of a heterogeneously catalysed transfer hydrogenation from H18-DBT to acetone and fuel cell operation with the resulting 2-propanol as a fuel, allows for an electrification of LOHC-bound hydrogen in high efficiency (> 50 %) and at surprisingly mild conditions (temperatures below 200 °C). Most importantly, our proposed new sequence does not require an external heat input as the transfer hydrogenation from H18-DBT to acetone is almost thermoneutral. In the PEMFC operation with 2-propanol, the endothermal proton release at the anode is compensated by the exothermic formation of water. Ideally the proposed sequence does not form and consume molecular H2 at any point which adds a very appealing safety feature to this way of producing electricity from LOHC-bound hydrogen, e.g. for applications on mobile platforms.Fil: Sievi, Gabriel. Forschungszentrum Jülich; AlemaniaFil: Geburtig, Denise. Universitat Erlangen-Nuremberg; AlemaniaFil: Skeledzic, Tanja. Forschungszentrum Jülich; AlemaniaFil: Bösmann, Andreas. Universitat Erlangen-Nuremberg; AlemaniaFil: Preuster, Patrick. Forschungszentrum Jülich; AlemaniaFil: Brummel, Olaf. Universitat Erlangen-Nuremberg; AlemaniaFil: Waidhas, Fabian. Universitat Erlangen-Nuremberg; AlemaniaFil: Montero, María de Los Angeles. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Khanipour, Peyman. Forschungszentrum Jülich; AlemaniaFil: Katsounaros, Ioannis. Forschungszentrum Jülich; AlemaniaFil: Libuda, Jörg. Universitat Erlangen-Nuremberg; AlemaniaFil: Mayrhofer, Karl J. J.. Forschungszentrum Jülich; AndorraFil: Wasserscheid, Peter. Universitat Erlangen-Nuremberg; Alemani

Solar energy storage at an atomically defined organic-oxide hybrid interface

Molecular photoswitches provide an extremely simple solution for solar energy conversion and storage. To convert stored energy to electricity, however, the photoswitch has to be coupled to a semiconducting electrode. In this work, we report on the assembly of an operational solar-energy-storing organic-oxide hybrid interface, which consists of a tailor-made molecular photoswitch and an atomically-defined semiconducting oxide film. The synthesized norbornadiene derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD) was anchored to a well-ordered Co3O4(111) surface by physical vapor deposition in ultrahigh vacuum. Using a photochemical infrared reflection absorption spectroscopy experiment, we demonstrate that the anchored CNBD monolayer remains operational, i.e., can be photo-converted to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC). We show that the activation barrier for energy release remains unaffected by the anchoring reaction and the anchored photoswitch can be charged and discharged with high reversibility. Our atomically-defined solar-energy-storing model interface enables detailed studies of energy conversion processes at organic/oxide hybrid interfaces

Selective electrooxidation of 2-propanol on Pt nanoparticles supported on Co3O4: an in-situ study on atomically defined model systems

2-Propanol and its dehydrogenated counterpart acetone can be used as a rechargeable electrofuel. The concept involves selective oxidation of 2-propanol to acetone in a fuel cell coupled with reverse catalytic hydrogenation of acetone to 2-propanol in a closed cycle. We studied electrocatalytic oxidation of 2-propanol on complex model Pt/Co3O4(111) electrocatalysts prepared in ultra-high vacuum and characterized by scanning tunneling microscopy. The electrocatalytic behavior of the model electrocatalysts has been investigated in alkaline media (pH 10, phosphate buffer) by means of electrochemical infrared reflection absorption spectroscopy and ex-situ emersion synchrotron radiation photoelectron spectroscopy as a function of Pt particle size and compared with the electrocatalytic behavior of Pt(111) and pristine Co3O4(111) electrodes under similar conditions. We found that the Co3O4(111) film is inactive towards electrochemical oxidation of 2-propanol under the electrochemical conditions (0.3–1.1 VRHE). The electrochemical oxidation of 2-propanol readily occurs on Pt(111) yielding acetone at an onset potential of 0.4 VRHE. The reaction pathway does not involve CO but yields strongly adsorbed acetone species leading to a partial poisoning of the surface sites. On model Pt/Co3O4(111) electrocatalysts, we observed distinct metal support interactions and particle size effects associated with the charge transfer at the metal/oxide interface. We found that ultra-small Pt particles (around 1 nm and below) consist of partially oxidized Pt δ + species which show minor activity towards 2-propanol oxidation. In contrast, conventional Pt particles (particle size of a few nm) are mainly metallic and show high activity toward 2-propanol oxidation

Photo- und Elektrochemie an Modellkatalysatoren für Energieumwandlung und Speicherung

This thesis focuses on several subjects of current research on energy storage and energy conversion. As main investigation tool, (photo-) electrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) was applied. This spectroscopic technique allows independent photo- and electrochemical in-situ measurements under well-defined conditions at atomically defined model electrodes. Following the electrochemical surface science approach, a fundamental understanding of reaction mechanisms and kinetics at the atomic level was derived

The energy transition and where mobility will go to

Enforced extension of renewable power will be required to achieve the targeted CO2 reduction. Hereby, it will be essential to shift renewable electricity to the mobility and industry sector. The transportation sector exhibits the highest need for action. Here the concept of the future will be electric. The main challenge will be the poor energy density of batteries compared to oil-based fuels. Trends and solutions for transportation via road, rail, sea and air are discussed in the paper.</jats:p

The energy transition and where mobility will go to

Enforced extension of renewable power will be required to achieve the targeted CO2 reduction. Hereby, it will be essential to shift renewable electricity to the mobility and industry sector. The transportation sector exhibits the highest need for action. Here the concept of the future will be electric. The main challenge will be the poor energy density of batteries compared to oil-based fuels. Trends and solutions for transportation via road, rail, sea and air are discussed in the paper