Lab

Axel Gross's Lab

About the lab

The group members of our lab are located at the Institute of Theoretical Chemistry of Ulm University and at the working group "Elementary Processes" of the Helmholtz Institute Ulm. The main research focus is on the theoretical modeling of structures and processes in (electro-)chemical energy conversion and storage at interfaces and in bulk materials.

Featured projects (1)

Project
Microscopic modeling of catalytic reactions at gas/solid and liquid/sold interfaces.

Featured research (19)

In this review, a discussion on renewable sources of energy with clear focus on solar cell applications is presented. Especially, possible future directions for development of dye-sensitized solar cells (DSSCs) are discussed. Dye-sensitized solar cells have become an important topic of research due to its high importance in energy conversion. Current DSSCs are based on either metal dye sensitizers, metal-free organic dyes or natural dyes. They have been extensively studied due to their low cost, simple preparation methodology, low toxicity, and ease of production. Still there is a need to find more abundant DSSC materials that at same time exhibit long-term stability. Computational studies have been an important ally for developing/designing new dye sensitizers. They are reviewed here with a special emphasis on the benefit of such studies. The conceptual understanding of development and working principle of photoactive DSSC materials are the primary feature of the review followed by examples of studies on different dye sensitizers using scarce to abundant metal based dyes and metal free organic dyes with donor-π-acceptor geometries for both n- and p-type DSSCs. The proper choice of organic dyes including donor, spacer, or acceptor is discussed and a prospective on dual donor based dyes is presented.
Bimetallic surfaces allow tailoring their catalytic activity by modifying their composition and/or structure. However, under operating conditions, catalytically active bimetallic structures are often not stable and change their morphology which might reduce their functionality. Still, catalytically active structures do not necessarily need to be thermodynamically stable and might also be kinetically stabilized. Here we report kinetic Monte Carlo simulations based on density functional theory calculation to address the meta-stability of surface alloy systems. As structural changes can typically only occur via vacancy diffusion in the surface, we first determine the vacancy diffusion barrier as a function of their bimetallic environment. By determining the temporal evolution of the bimetallic surface alloys as a function of temperature, we analyze the factors underlying the stability and structure of the bimetallic surface alloys.
Structures and processes at water/metal interfaces play an important technological role in electrochemical energy conversion and storage, photoconversion, sensors, and corrosion, just to name a few. However, they are also of fundamental significance as a model system for the study of solid−liquid interfaces, which requires combining concepts from the chemistry and physics of crystalline materials and liquids. Particularly interesting is the fact that the water−water and water−metal interactions are of similar strength so that the structures at water/metal interfaces result from a competition between these comparable interactions. Because water is a polar molecule and water and metal surfaces are both polarizable, explicit consideration of the electronic degrees of freedom at water/metal interfaces is mandatory. In principle, ab initio molecular dynamics simulations are thus the method of choice to model water/metal interfaces, but they are computationally still rather demanding. Here, ab initio simulations of water/metal interfaces will be reviewed, starting from static systems such as the adsorption of single water molecules, water clusters, and icelike layers, followed by the properties of liquid water layers at metal surfaces. Technical issues such as the appropriate first-principles description of the water−water and water−metal interactions will be discussed, and electrochemical aspects will be addressed. Finally, more approximate but numerically less demanding approaches to treat water at metal surfaces from first-principles will be briefly discussed.
Magnesium Batteries Ion mobility is a critical parameter contributing to the performance of batteries. In article number 2100113 by Axel Groß and co-workers, the site preference of ions in battery electrodes and solid electrolytes is determined as a function of volume by quantum chemical calculations. The results reveal that an analysis purely based on electrostatic interactions is inadequate for capturing all factors influencing ion mobility and stability in these materials.
Conductive polymers represent a promising alternative to semiconducting oxide electrodes typically used in dye-sensitized cathodes as they more easily allow a tuning of the physicochemical properties. This can then also be very beneficial for using them in light-driven catalysis. In this computational study, we address the coupling of Ru-based photosensitizers to a polymer matrix by combining two different first-principles electronic structure approaches. We use a periodic density functional theory code to properly account for the delocalized nature of the electronic states in the polymer. These ground state investigations are complemented by time-dependent density functional theory simulations to assess the Franck-Condon photophysics of the present photoactive hybrid material based on a molecular model system. Our results are consistent with recent experimental observations and allow to elucidate the light-driven redox chemical processes – eventually leading to charge separation – in the present functional hybrid systems with potential application as photocathode materials.

Lab head

Axel Gross
Department
  • Institute of Theoretical Chemistry
About Axel Gross
  • Axel Gross currently works at the Institute of Theoretical Chemistry, Ulm University, and at the Helmholtz-Institute Ulm. Axel does research in Theoretical Chemistry, Surface Chemistry and Electrochemistry. Their current projects are related to (electro-)chemical energy conversion and storage at interfaces and in bulk materials. Axel is one of the three spokespersons of the Cluster of Excellence POLiS (Post-Li Energy Storage) funded by the German Science Foundation.

Members (17)

Sung Sakong
  • Ulm University
Fernanda Juarez
  • Ulm University
Katrin Forster-Tonigold
  • Helmholtz Institute Ulm
Kanchan Sarkar
  • Indian Association for the Cultivation of Science
Majid Rezaei
  • Ulm University
Mohsen Sotoudeh
  • Ulm University
Li Mengru
  • Ulm University

Alumni (17)

Holger Euchner
  • University of Tuebingen
Tanglaw Roman
  • The University of Sydney
Christian Carbogno
  • Fritz Haber Institute of the Max Planck Society
Yoshihiro Gohda
  • Tokyo Institute of Technology