Priv.-Doz. Dr. Simon Penner und assoz. Prof. Dr. Bernhard Klötzer
Model Catalysis
Priv.-Doz Dr. Simon Penner
+43 (512) 507 58003
assoz. Prof. Dr. Bernhard Klötzer
+43 (512) 507 58004
Our group is devoted to a mechanistic understanding of processes occurring at the solid-gas interface in reactions relevant for sustainable catalysis, like methanol steam or dry reforming or the selective catalytic reduction of nitrous oxides. Materials range from pure oxides over metal-oxide systems to intermetallic compounds and alloys. Through connection of model system studies under ultrahigh vacuum conditions to powder systems characterized under technologically relevant conditions our goal is to close the “pressure” and “materials” gaps in catalysis. Our approach is the exclusive use of in situ and operando spectroscopic and structural methods to investigate catalyst materials under close-to-real conditions. This interdisciplinary approach usually involves collaboration from various research areas, encompassing materials science, chemistry, physics or chemical engineering.
Sub-stoichiometry on the A-site in a lanthanum-iron-manganese perovskite enhances the reactivity and nitrogen selectivity in the selective catalytic reduction of NO by CO.
The project focuses on mixed ionic-electronic conductors in a novel class of highly ordered, chemically and structurally highly complex oxide materials, e.g., on lanthanum-copper-manganese or lanthanum-iron-manganese basis for in situ activation through exsolution of small metal particles and the associated formation of metal-perovskite interfaces. The physico-chemical properties of the latter can be directly steered through synthesis and activation and therefore these interfaces exhibit the potential to replace existing noble metal-based materials in energy- and environmentally relevant reactions, such as the selective catalytic reduction of NO by CO. The key topic is retaining the structural stability and/or steering of the stability of the interface by simultaneously keeping beneficial catalytic properties (number and distribution of oxygen vacancies, surface and redox chemistry) under operational conditions. Through monitoring the structural or spectroscopic changes live under typical reaction conditions by in situ methods, we are able to gain fundamental insight into the structural and chemical dynamics of those materials and to establish unambiguous structure-activity relationships.
This project deals with the activation of reactive carbon species during methane dry reforming. Central goal is an improved design of coke-resistant methane dry reforming catalysts on perovskite- and intermetallic/alloy-based materials with enhanced long-term and thermochemical stability. Through adequate choice of oxide or intermetallic compound precursors, we are able to tune the chemical and structural features of the reactive carbon intermediates within the dry reforming network. Methodologically, we exclusively rely on in situ and operando characterization of catalysts in their working state, which again enables us to connect catalytic and structural properties directly.
Ni exsolution from a Sr2NiMoO6 double perovskite during methane dry reforming and associated formation of a Ni-double perovskite interface (top) and formation of a reactive zirconium carbide phase in a carbon dioxide-methane mixture during the in situ activation of a Ni-Zr alloy and the associate formation of a Ni-ZrO2 interface (bottom).
Solid oxide fuel cell technologies are essential for the storage of renewable energy and de-carbonisation. To push these technologies, a functional understanding of electrocatalytic materials under high-temperature conditions is imperative. Operando-based spectroscopic investigations, e.g., by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) allow for unique insights into the chemical nature of active working electrodes, including the reactivity of different redox states and the adsorbate chemistry under dynamically changing electrochemical conditions. Thin-film model cells with spectroscopically accessible triple-phase boundary (TPB) regions for studies of interface states and local electrochemical processes deliver a fundamental understanding for the further development of renewable energy storage technologies.
Atomic force microscopic (A, D) and scanning electron images (B, E) of a Ni/8-YSZ thin film model cell annealed at 1073 K (left) and 1123 K (right). Energy-dispersive X-ray maps with associated chemical information are shown in Panels C and F. Height profiles in Panels A and D deliver additional information on the local structure of the Ni thin film as a function of annealing temperature.