In the etzoldlab

In the etzoldlab the challenges arising with the needed global energy change and future sustainable feedstock supply for chemical industry are the major research guideline. From the perspective of applied chemistry, a multidisciplinary approach is employed to provide scientific solutions for these challenges, especially for the complex interplay of catalytic materials within a full process or device. In the scientific approach, generic experiments play a dominant role. They allow controlling process conditions from highly idealized towards technically realistic and are combined with diagnostics providing in-situ information. Chemical reaction engineering simulations complement the experiments, giving especially insights into complex mass transfer phenomena and, therefore making a more holistic picture possible. As a future sustainable energy and chemical industry will need a concerted interaction of electrochemical and classical heterogeneous catalyzed processes both are studied. Based on this strategy, the research of the etzoldlab can be divided in three strongly interacting sub-groups: Advanced Catalytic Materials – Electrochemical Energy Conversion Processes – Heterogeneous Catalysis and Processes. More details on the research of these subgroups can be found in the sections below.

With our research we are part of the following huger or collaborative research activities:

The special focus lies on the development of carbon-based materials for catalysis in form of versatile supports or as catalysts themselves. In order to ensure a high reproducibility and highly pure materials, polymers and carbides are employed as the carbon precursors. Particular attention is paid to the precise control of the pore structure from the sub-nanometer towards the mm scale, including spatially varying properties. In this sense, core/shell carbon particles as well as hierarchically structured open cellular materials are prepared. For the later one an unprecedented high degree of freedom is available through a newly developed stereolithographic 3D printing route. For catalytic applications, surface functional groups are introduced or noble and base metals are deposited in controlled amount, size and shape on these carbons by various methods. The in-depth material characterization is the cornerstone in the etzoldlab to connect the resulting material properties with the synthesis procedure and conditions. Among the variety of characterization techniques applied, a special focus is on high-resolution physi- and chemisorption and thermogravimetric analysis coupled with mass spectrometry.

A,B) SEM images of a 3D porous carbon in a spiral macrostructure; C) 3D printed porous carbon open-cell structure supporting the weight of a 1.7 kg steel cylinder.

In electrochemical energy conversion processes the complex interplay of activity/selectivity and mass transfer of catalytic materials and carbonaceous electrodes in multiphase (gas/liquid) systems is studied. Processes are the polymer electrolyte fuel cell and electrolysis as also the CO2 reduction. In this sense catalysts for the ORR, HER, OER and CO2RR are studied. For boosting activity, selectivity and stability in these reactions an innovative approach, complementary to tuning nanoparticle properties, is employed. In this approach tiny amounts of Ionic Liquid (IL) are employed to modify the active site microenvironment. This SCILL approach (Solid Catalyst with Ionic Liquid Layer) was pioneered by us for heterogeneous catalysis in 2007 and is studied intensively, to leverage its full potential in electrocatalysis. As classical rotating disc electrode (RDE) studies are strongly limited in the achievable current density and cannot reach potentials where technical systems operate and furthermore show no true triple-phase-boundary, further efforts are needed to study catalysts under technical relevant conditions. For this purpose, in the etzoldlab on the one hand half cells based on gas-diffusion-electrodes are employed, which allows to study a triple-phase-boundary on a single half cell side without interference from either the counter reaction or polymer electrolyte membrane. On the other hand full membrane electrode assembly (MEA) testing is carried out on fuel cell testing stations. Important cornerstone for both techniques is the highly accurate and reproducible deposition of catalyst layers, which is carried out by robot assisted ultrasound spraying.

A) Boosting effect of imidazolium based cations with different alkyl chain length and [NTf2] as anions for platinum catalyst in ORR@0.9V; B) Schematic of half cell based on a gas-diffusion-electrode for achieving high current densities and technical relevant potentials.

The research in heterogeneous catalysis bridges from screening towards detailed mechanistic studies as also from intrinsic kinetics to full process consideration. In this sense, transient-response-studies including isotope labeling (SSITKA), in-situ DRIFT and Raman spectroscopy are employed as also long-term catalyst studied in continuously operated rigs. These insights are complemented by kinetic and thermodynamic simulation as also flow sheeting. The later one gives insights how changes in catalyst activity and selectivity affect the up- and down-stream processes and e.g. total energy consumption or feedstock efficiency. Chemical conversions studied belong to the base chemical and gas phase sector. The focus is on partial oxidations like oxidative dehydrogenation and CO/CO2/H2 conversion to methanol and Fischer-Tropsch products.

A) Experimentally determined and simulated conversion of acrolein from steady‐state measurements and cyclic TPReaction experiment on 50Mo8V2W1.5Ox. The arrows mark the curve of the positive (β = 10 °C min−1) and negative (β = −10 °C min−1) heating rate; B) Process concept for synthesis of CH3OH from CO2 and H2 making use of in-situ phase separation.
  • Advanced Catalytic Materials
  • Horizontal tubular furnaces for gas/solid reactions under corrosive atmosphere (Cl2) up to 1600°C.
  • Vacuum furnace up to 2000°C
  • (Vacuum) hot press up to 450°C
  • Stereolithographic 3D printer
  • Electrode production line (automated doctorblade, calendering, sealing)
  • High resolution physisorption and chemisorption (Ar, N2, CO2, CO, H2, …)
  • Thermogravimetry coupled with mass spectroscopy
  • Electrochemical Energy Conversion Processes
  • Several ®RDE workstations with multichannel potentiostats
  • Gas-diffusion-electrode half cells
  • Robot assisted ultrasound nozzle spraying station
  • Fuel cell testing stations
  • CO2 electroreduction half cells with online GC
  • Heterogeneous Catalysis and Processes
  • Transient response testing stations with high resolution mass spectroscopy and GC (for TPR, CPR and SSITKA studies)
  • In-situ raman microscope for spatially resolved spectra coupled to an operando GC
  • In-situ DRIFTS cells with operando gas analysis
  • Continuous flow gas phase catalyst rigs with online analytics (GCs, FTIRs, MS, …)