Eindhoven, Netherlands
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Sapountzi F.M.,Syngaschem BV | Gracia J.M.,Synfuels China Technology Co. | Weststrate C.J.K.-J.,Syngaschem BV | Fredriksson H.O.A.,Syngaschem BV | And 2 more authors.
Progress in Energy and Combustion Science | Year: 2017

Water electrolysis is the most promising method for efficient production of high purity hydrogen (and oxygen), while the required power input for the electrolysis process can be provided by renewable sources (e.g. solar or wind). The thus produced hydrogen can be used either directly as a fuel or as a reducing agent in chemical processes, such as in Fischer–Tropsch synthesis. Water splitting can be realized both at low temperatures (typically below 100 °C) and at high temperatures (steam water electrolysis at 500–1000 °C), while different ionic agents can be electrochemically transferred during the electrolysis process (OH−, H+, O2−). Singular requirements apply in each of the electrolysis technologies (alkaline, polymer electrolyte membrane and solid oxide electrolysis) for ensuring high electrocatalytic activity and long-term stability. The aim of the present article is to provide a brief overview on the effect of the nature and structure of the catalyst–electrode materials on the electrolyzer's performance. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The current trends, limitations and perspectives for future developments are summarized for the diverse electrolysis technologies of water splitting, while the case of CO2/H2O co-electrolysis (for synthesis gas production) is also discussed. © 2016 The Authors

Gracia J.,Syngaschem BV | Escuin M.,University of Zaragoza | Mallada R.,University of Zaragoza | Mallada R.,CIBER ISCIII | And 3 more authors.
Nano Energy | Year: 2016

It has been experimentally observed that, in some Mott nanomaterials, outstanding dielectric losses may appear at microwave frequencies, leading to a rapid increase of temperature. This often takes place in association with the insulator to metal transition (IMT) in these materials. However, when other materials with a similar structure and composition are subjected to the same intensity of microwave (MW) irradiation, the observed heating is minimal. Here we show that the electron dynamics of these materials are responsible for their different heating behaviour. More specifically, for LaCoO3 perovskite nanoparticles, the spin shifts causing the IMT are also responsible for the observed heating behaviour. Under suitable conditions, the intense absorption of MW radiation leads to extremely high heating rates, above 600 degrees per second. The insight gained from this study has been used to design a directly heated catalytic system (LaCoO3 perovskite nanoparticles on a MW-transparent cordierite monolith) capable to operate under a stable, significant solid-gas temperature gradient. © 2015 The Authors.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: NMP-23-2015 | Award Amount: 4.37M | Year: 2016

The CritCat proposal aims to provide solutions for the substitution of critical metals, especially rare platinum group metals (PGMs), used in heterogeneous and electrochemical catalysis. CritCat will explore the properties of ultra-small transition metal (TM) nanoparticles in order achieve optimal catalytic performance with earth-abundant materials. The emphasis will be on industrially-relevant chemical reactions and emerging energy conversion technologies in which PGMs play an instrumental role, particularly in the context of hydrogen and synthesis gas (syngas) fuels. The CritCat proposal includes all the aspects for rational catalyst design including novel catalyst synthesis, characterization, and performance testing by a range of academic and industry partners together with large-scale computational simulations of the relevant catalysts, substrates and model reactions using the latest computational methods. Particular attention is given to a strong feedback-loop mechanism where theory is an integral part of the experimental work packages. The experimental and theoretical data will be collected (descriptor database) and used for materials screening via machine learning techniques and new algorithms. The goal is to improve size, shape and surface structure control of the tailored nanoparticle catalysts via novel cluster/nanoparticle synthesis techniques that can produce samples of unrivalled quality. The research includes up-scaling of the size-selected catalyst nanoparticle samples up to macroscopic quantities, which will enable them to be included as basic technological components for realistic catalyst systems. The performance of the catalyst prototypes will be demonstrated for selected basic electrochemical reactions relevant to fuel cells and storage of renewable energy. The industrial partners bring their expertise in prototypes development and commercial deployment (TRL 3-4). The project involves cooperation with external research groups in USA and Japan.

Weststrate C.J.,Syngaschem BV | van Helden P.,Sasol Limited | Niemantsverdriet J.W.,SynCat@DIFFER
Catalysis Today | Year: 2016

The current paper presents a mechanistic view on important steps in the Fischer-Tropsch synthesis on cobalt catalysts, inspired by surface science studies. By revisiting the relation between activity and selectivity that results from the ASF assumption we highlight that knowledge about the number of growing chains as well as their residence time (∼growth rate) is of crucial importance to sketch a physically realistic scenario for FTS. This motivates further investigations into the microscopic scenario for FTS chain growth on fcc cobalt nanoparticles, by looking into the reaction mechanism in relation to surface structure and by determining the activation energies for key elementary steps. Such studies indicate that the modest activity of Co FTS catalysts might very well be attributable to the difficulty to remove chemisorbed oxygen from the metallic surface, rather than to dissociation of CO, which was found to proceed readily at step edge sites. Chain growth is envisaged to take place on the close-packed surfaces, with chain initiation via CH+CH to form acetylene, followed by hydrogenation to form ethylidyne, CCH3, a reaction that is shown to be promoted by co-adsorbed CO. Ethylidyne then couples with CH to form propyne, HCCCH3, etc. We propose that a fairly large number of surface sites is involved in the growth of a single chain. In such a "growth ensemble" multiple active step sites produce CHx monomer species that spill over onto the same close-packed coupling terrace, where one or only a few chains grow at the same time. In such a scenario diffusion of hydrocarbonaceous surface species is an essential step in the overall reaction sequence. We explore which factors need to be taken into account when considering of CxHy species under realistic reaction conditions. In addition, we note that the coupling reaction itself, via CH+CCnH2n+1, is a source of growing chain mobility. © 2016 Elsevier B.V.

Ozbek M.O.,TU Eindhoven | Ozbek M.O.,Syngaschem BV | Niemantsverdriet J.W.,TU Eindhoven | Niemantsverdriet J.W.,Syngaschem BV
Journal of Catalysis | Year: 2014

CO and H2 (co-)adsorption, direct and H-assisted CO activation, and surface carbon hydrogenation were investigated on C-terminated χ-Fe 5C2(0 0 1) surfaces. Periodic DFT simulations at different surface carbon contents on the carbide surface showed that CO adsorbs preferably linearly on Fe top sites; CO and H2 adsorptions being stable. The perfect carbide surface favors carbidic carbon hydrogenation (i.e. CH formation), whereas carbon-free surface favors direct CO dissociation and restoration of the carbide structure. In partially carbon-vacant intermediate situations, both direct and H-assisted CO activations are energetically feasible, the latter being the preferred path. Considering CHx and CHxO species as initiators for different product types can explain the catalytic behavior and selectivity patterns of iron carbide catalysts. The catalytically active surfaces are concluded to be dynamic, where carbon atoms of the carbide surface participate in the surface reactions, and CO dissociation on vacant sites leads to restoration of the carbide structure. © 2014 Elsevier Inc. All rights reserved.

Ozbek M.O.,TU Eindhoven | Ozbek M.O.,Syngaschem BV | Ozbek M.O.,Yeditepe University | Niemantsverdriet J.W.,TU Eindhoven | Niemantsverdriet J.W.,Syngaschem BV
Journal of Catalysis | Year: 2015

Formation of CHx(O) monomers and C1 products (CH4, CH2O, and CH3OH) on C-terminated χ-Fe5C2(0 0 1) (Hägg carbide) surfaces of different carbon contents was investigated using periodic DFT simulations. Methane (CH4) as well as monomer (CHx) formation follows a Mars-van Krevelen-like cycle starting with the hydrogenation of surface carbidic carbon, which is regenerated by subsequent CO dissociation, while oxygen is removed as H2O. In cases where surface carbon is readily available, the apparent barrier for CH4 formation was found to be ∼95 kJ/mol. However, different rate-determining steps show that different propagation mechanisms may be possible for actual chain growth, depending on the carbon content of the surface. Hydrogen addition to CO forms formyl (HCO), which is a precursor for both H-assisted CO activation and oxygenate formation. Further hydrogenation of HCO yields adsorbed formaldehyde and methoxy, rather than hydroxymethyl (HCOH) that would give C-O bond splitting. Full hydrogenation to gas-phase methanol faces a high barrier, suggesting that CHxO species may be involved in higher oxygenate formation in a full Fischer-Tropsch mechanism or that the C-O bond does not break until the CHO fragment has been incorporated in a C2 species, a route for which precedents are available in the literature. © 2015 Elsevier Inc. All rights reserved.

Bu Y.,TU Eindhoven | Niemantsverdriet J.W.H.,Syngaschem BV | Niemantsverdriet J.W.H.,Synfuels China Technology Co. | Fredriksson H.O.A.,TU Eindhoven | Fredriksson H.O.A.,Syngaschem BV
ACS Catalysis | Year: 2016

The oxidation state of Cu nanoparticles during CO oxidation in CO + O2 gas mixtures was sensitively monitored via localized surface plasmon resonances. A microreactor, equipped with in situ UV-vis and mass spectrometry, was developed and used for the measurements. Cu nanoparticles of ∼30 nm average diameter were supported on optically transparent, planar quartz wafers. The aim of the study is 2-fold: (i) to demonstrate the performance and usefulness of the setup and (ii) to use the combined strength of model catalysts and in situ measurements to investigate the correlation between the catalyst oxidation state and its reactivity. Metallic Cu is significantly more active than both Cu(I) and Cu(II) oxides. The metallic Cu phase is only maintained under conditions where close to full oxygen conversion is achieved. This implies that kinetic measurements, aimed at determining the apparent activation energy for metallic Cu under realistic steady-state conditions, are difficult or impossible to perform. © 2016 American Chemical Society.

PubMed | University of the Free State and Syngaschem BV
Type: Journal Article | Journal: Molecules (Basel, Switzerland) | Year: 2016

A series of ferrocenyl-functionalized -diketonato manganese(III) complexes, [Mn(FcCOCHCOR)] with R = CF, CH, Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p

Weststrate C.J.,Syngaschem BV | van de Loosdrecht J.,Sasol Limited | Niemantsverdriet J.W.,Syngaschem BV | Niemantsverdriet J.W.,Synfuels China Technology Co.
Journal of Catalysis | Year: 2016

The present article summarizes experimental findings of the interaction of CO with single crystal surfaces of cobalt. We first provide a quantitative study of non-dissociative CO adsorption on Co(0001) and establish a quantitative correlation between θCO and adsorption site occupation. In light of these findings we revisit the structure of previously reported ordered CO/Co(0001) adsorbate layers. Measurements of the CO coverage at equilibrium conditions are used to derive a phase diagram for CO on Co(0001). For low temperature Fischer-Tropsch synthesis conditions the CO coverage is predicted to be ≈0.5 ML, a value that hardly changes with pCO. The CO desorption temperature found in temperature programmed desorption is practically structure-independent, despite structure-dependent heats of adsorption reported in the literature. This mismatch is attributed to a structure-dependent pre-exponential factor for desorption. IR spectra reported throughout this study provide a reference point for IR studies on cobalt catalysts. Results for CO adsorbed on flat and defect-rich Co surfaces as well as particular, CO adsorbed on top sites, and in addition affect the distribution of COad over the various possible adsorption sites. © 2016 Elsevier Inc.

Lim T.,Synfuels China Technology Co. | Niemantsverdriet J.W.H.,Synfuels China Technology Co. | Niemantsverdriet J.W.H.,Syngaschem BV | Gracia J.,Synfuels China Technology Co.
ChemCatChem | Year: 2016

We have performed an in-depth ab initio study of the magnetic structure within the most active perovskites for the oxygen evolution reaction. In all cases, the ground state exhibits an extended antiferromagnetic coupling in the unit cell. Layered antiparallel alignment of the magnetic moments appears to be related to their electrocatalytic activity. All the perovskites calculated within this paper show space-separated charge-transport channels depending on the spin orientation. Comparing the electronic structures with the reported activities, we find a direct correlation between the magnetic accumulation on the spin channels in the bulk material and the catalytic activity. We discuss the possible implications of such observations in terms of magnetic interactions. During oxygen evolution in water electrolysis, reactants and products do not preserve spin. For triplet state oxygen to evolve, the catalyst at the anode can speed up the reaction if it is able to balance the magnetism of the oxygen molecule by extracting electrons with an opposite magnetic moment, conserving the overall spin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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