Thomas Kropp

• Dr. rer. nat.
• PostDoc Position at Fritz Haber Institute of the Max Planck Society

We employed an approach combining reaction kinetics measurements at steady state conditions, electronic structure calculations employing density functional theory, and microkinetic modeling for acetone hydrogenation to provide insights into the effects of water on metal catalyst surfaces for the hydrogenation of oxygenates over a wide range of reac...

The effect of strain on the adsorption of atomic species (Cl, H, N, and O) on pristine and nitrogen-doped graphene is studied using density functional theory. Expansive strain increases surface reactivity by destabilizing graphene π orbitals, which is similar to the shift in the d-band center observed on stretched metal surfaces. However, compressi...

Graphene-based single-atom catalysts are promising alternatives to platinum-based catalysts for fuel cell applications. Different transition metals have been screened using electronic structure methods by estimating onset potentials from the most endergonic elementary reaction step. We calculate onset potentials for the oxygen reduction reaction on...

Significance A collaborative approach containing reaction kinetics measurements under steady-state and transient conditions, electronic structure calculations employing density-functional theory, and microkinetic modeling on acetone hydrogenation is employed to provide insights into understanding the self-adjusting platinum surface for the hydrogen...

Transition-metal atoms embedded in nitrogen-doped graphene can be used for electrocatalytic water splitting, but there are open questions regarding the identity of the active site. We study the formation of hydrogen and oxygen as well as the reduction of oxygen on 14 transition metals embedded in nitrogen-doped graphene using density functional the...

Scaling relations are widely used to model catalytic reactions on metal surfaces, but they are less commonly applied to metal oxides. Oxygen vacancy formation energies have been suggested as a descriptor for the activity toward oxidation reactions via the Mars-van Krevelen mechanism. However, there is currently no function that maps oxygen vacancy...

Catalytic performance is known to be influenced by several factors, with the catalysts’ surface oxidation state being the most prominent of all. However, in the great majority of industrial heterogeneous catalytic reactions the oxidation state of the active sites is a subject of intense debate. Preferential oxidation of carbon monoxide in hydrogen...

We study 14 transition metals on pristine and N-doped graphene using density functional theory. For double vacancies, nitrogen doping increases the binding strength of harder transition metals to the support and reduces their oxygen affinity. Inversely, the oxygen affinity of softer metals increases. Since O2 binding energies are correlated with th...

We study 14 atomically dispersed transition metals on halite-type oxides (MeO, Me = Fe, Mg, Mn, and Ni) using periodic density functional theory calculations and probe structure and activity toward CO oxidation for a subset of these systems experimentally. Pd and Pt can form stable negatively charged species upon binding to oxygen vacancies; the ma...

The alteration of electrocatalytic surfaces with adatoms lead to structural and electronic modifications promoting adsorption, desorption, and reactive processes. This study explores the potentiostatic electrodeposition process of Ni onto polycrystalline Ir (Irpoly) and assesses the electrocatalytic properties of the resulting bimetallic surfaces....

Ceria (CeO2) has recently been found to be a promising catalyst in the selective hydrogenation of alkynes to alkenes. This reaction occurs primarily on highly dispersed metal catalysts, but rarely on oxide surfaces. The origin of the outstanding activity and selectivity observed on CeO2 remains unclear. In this work, we show that one key aspect of...

An atomic-level understanding of dioxygen activation on metal oxides remains one of the major challenges in heterogeneous catalysis. By performing a thorough surface-science study of all three low-index single-crystal surfaces of ceria, probably the most important redox catalysts, we provide a direct spectroscopic characterization of reactive dioxy...

An atomic-level understanding of dioxygen activation on metal oxides remains one of the major challenges in heterogeneous catalysis. By performing a thorough surface-science study of all three low-index single-crystal surfaces of ceria, probably the most important redox catalysts, we provide a direct spectroscopic characterization of reactive dioxy...

This density functional theory study compares water adsorption on the ceria (111) and (100) surfaces. In the absence of water, the (111) surface is more stable than the polar (100) surface, but at higher water coverages the (100) surface is favored due to the formation of a highly stable “square ice” layer on top of the fully hydroxylated surface....

We study the adsorption and partial oxidation of methanol at a trimeric VOX species supported on ceria, which was found to be the thermodynamically most stable species under slightly reducing conditions. Results for the oxidation of methanol obtained using dispersion-corrected PBE+U and HSE are compared with a metastable monomeric VO2 species. The...

Unter Verwendung von Dichtefunktionaltheorie werden die katalytischen Eigenschaften von Cerdioxidoberflächen mit verschiedenen Terminierungen untersucht. Cerdioxid wird auch als Trägermaterial in der heterogenen Katalyse eingesetzt, um Aktivität, Selektivität und Stabilität der aktiven Komponente zu erhöhen. In dieser Arbeit werden geträgerte Vanad...

We have studied the adsorption of methanol on the (1 1 0) and (1 1 1) surfaces of bulk ceria (CeO2) single crystals using infrared reflection–absorption spectroscopy (IRRAS). To assign the experimentally observed features, density functional theory (DFT) has been applied. For ceria (1 1 0), only a single intense band at 1108 cm−1 is observed, which...

Ceria nanoparticles may expose (100) and (111) facets depending on the preparation method. Motivated by that, we study the reactions of methanol with the CeO2(100) surface using dispersion-corrected PBE+U subject to periodic boundary conditions and compare with results for the CeO2(111) surface. At (100) facets, the oxidative dehydrogenation of met...

We study the dissociative adsorption and oxidative dehydrogenation of methanol at the pristine and O-defective ceria (111) surfaces to understand the role of surface oxygen vacancies. The accuracy of two density functional theory based approaches (PBE+U and the HSE hybrid functional) is assessed on available experimental data. In addition, the impa...

Density functional theory is used for periodic models of monomeric vanadia species deposited on the CeO2(111) surface to study dissociative adsorption of methanol and its subsequent dehydrogenation to formaldehyde. Dispersion-corrected PBE+U calculations are performed and compared with HSE and B3LYP results. Dissociative adsorption of methanol at d...

By virtue of periodic density functional theory, we investigate structure and thermodynamic stability of (VO)k and (VO2)k (k = 1, 2, 3) clusters deposited on the CeO2(111) surface, which serve as models for the very active sub-monolayer vanadia catalyst on a ceria support. We find V always completely oxidized (oxidation state +5) and coordinated to...