Axel Gross

Ulm University | UULM · Institute of Theoretical Chemistry

Based on quantum chemical calculations, we predict strong solvatochromism in a light‐driven molecular photocatalyst for hydrogen generation, i.e., we show that the electronic and optical properties of the photocatalyst strongly depend on the solvent it is dissolved in. Our calculations in particular indicate a solvent dependent relocation of the hi...

The electrification of the transportation sector exacerbates all issues concerning the use of critical materials in state-of-the-art batteries and, therefore, urges the development of new technologies based on potentially greener and more abundant materials. One research trend is the substitution of Li as shuttle ion with other elements such as Na,...

Prussian whites (PW) have gained attention for their potential application as high energy density cathodes in Na‐ion batteries. However, the rhombohedral phase of this compound still remains elusive. This study addresses the electronic and structural properties of the rhombohedral host material, as well as its ionic conductivity. Using periodic den...

Ion mobility in electrolytes and electrodes is an important performance parameter in electrochemical devices, particularly in batteries. In this review, we concentrate on the charge carrier mobility in crystalline battery materials where the diffusion basically corresponds to hopping processes between lattice sites. However, in spite of the seem- i...

The high ionic conductivity and good oxidation stability of halide-based solid electrolytes evoke strong interest in this class of materials. Nonetheless, the superior oxidative stability compared to sulfides comes at the expense of limited stability toward reduction and instability against metallic lithium anodes, which hinders their practical use...

Accurate modeling of highly concentrated aqueous solutions, such as water-in-salt (WiS) electrolytes in battery applications, requires proper consideration of polarization contributions to atomic interactions. Within the force field molecular dynamics (MD) simulations, the atomic polarization can be accounted for at various levels. Nonpolarizable f...

The increasing need for electrochemical energy storage drives the development of post-lithium battery systems. Among the most promising new battery types are sodium-based battery systems. However, like its lithium predecessor, sodium batteries suffer from various issues like parasitic side reactions, which lead to a loss of active sodium inventory,...

Conversion of CO2 to hard carbon is an interesting technology for the removal of carbon dioxide from the atmosphere. Recently, it was shown that CeO2 can selectively catalyse this reaction but we still lack information regarding the reaction mechanism. Using density functional theory (DFT) modelling we explore possible reaction mechanisms that allo...

The research of new electrode materials such as sodium intercalation compounds is key to meet the challenges of future demands of sustainable energy storage. For these batteries, the intercalation behaviour on the micro-scale is governed by a complex interplay of chemical, electrical and mechanical forces strongly influencing the overall cell perfo...

The transition from lithium‐based energy storage to post lithium systems plays a crucial part in achieving an environmentally sustainable energy infrastructure. Prime candidates for the replacement of lithium are sodium and potassium batteries. Despite being critical to battery performance, the solid electrolyte interphase (SEI) formation process f...

The modelling of electrochemical interfaces between a liquid electrolyte and an electrode from a quantum chemical perspective is typically done by performing ab initio molecular dynamics simulations. Thus the statistically nature of the electrolyte structure can be taken into account by performing the proper averages. However, in order to obtain re...

The diffusion of adsorbed O atoms on a CO-covered Ru(0001) surface has recently been explained by a “door-opening” mechanism which is driven by fluctuations in the CO layer. Here, we analyze how this mechanism changes at a higher CO coverage than the 0.33 monolayers applied in the previous study and, therefore, lower concentrations of empty sites....

The transition from lithium-based energy storage to post lithium systems plays a crucial part in achieving an environmentally sustainable energy infrastructure. Prime candidates for the replacement of lithium are sodium and potassium batteries. Despite being critical to battery performance, the solid electrolyte interphase (SEI) formation process f...

Mg batteries with oxide cathodes have the potential to significantly surpass existing Li-ion technologies in terms of sustainability, abundance, and energy density. However, Mg intercalation at the cathode is often severely hampered by the sluggish kinetics of Mg$^{2+}$ migration within oxides. Here we report a combined theoretical and experimental...

(50 days' free access: https://authors.elsevier.com/a/1giEc_8dCCsvFr) The cathode material Na$_x$FePO$_4$ of sodium-ion batteries exhibits complex phase segregation thermodynamics with the existence of an intermediate phase, and large volume change during (dis)charging. A virtual multiscale modeling chain is established to construct a 3D anisotrop...

To model a NaOTF Water-in-Salt (WiS) electrolyte using classical Molecular Dynamics (MD) simulations, we explore various force fields where atomic polarization is accounted for at three different levels: a non-polarizable all-atom force field where polarization is only implicitly included in its Van der Waals interaction parameters, the same force...

The theoretical modeling of metal/water interfaces centers on an appropriate configuration of the electric double layer (EDL) under grand canonical conditions. In principle, ab initio molecular dynamics (AIMD) simulations would be the appropriate choice for treating the competing water-water and water-metal interactions and explicitly considering t...

Based on quantum chemical calculations, we predict strong solvatochromism in a light-driven molecular photocatalyst for hydrogen generation, i.e., we show that the electronic and optical properties of the photocatalyst strongly depend on the solvent it is dissolved in. Our calculations in particular indicate a solvent dependent relocation of the hi...

Mixing dopants into oxide catalysts can improve the catalytic activity, as shown in the dramatic boost of the NH3 selective catalytic reduction (SCR) activity on vanadia catalysts upon doping by tungsten. Thus, the design and optimization of oxide catalysts require a precise understanding of the role of dopants and their influence on catalytic reac...

Density functional theory calculations together with ab initio molecular dynamics (AIMD) simulations have been used to study the solvation, diffusion and transformation of Li⁺ and LiO2 upon O2 reduction in three organic electrolytes. These processes are critical for the performance of Li-air batteries. Apart from studying the structure of the solva...

Electrocatalytic activity is influenced by the surface charge on the solid catalyst. Conventionally, our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s) in the local reaction zone. Taking H2O2 redox reactions at Pt(111) as a model system, we reveal a peculiar surface charge e...

The Front Cover illustrates the chemical reactions of an ionic liquid with Li atoms. Combining experiment and theory, initial products in the solid‐electrolyte interphase formation are clearly identified. More information can be found in the Research Article by K. Forster‐Tonigold and co‐workers.

Invited for this month's cover picture is the work of Prof. Groß’ and Prof. Behm's groups at the Helmholtz Institute Ulm (HIU) Electrochemical Energy Storage and Ulm University. The cover picture shows the model study on the chemical reactions of the ionic liquid BMP‐TFSI with Li atoms. The combined study of XPS experiments and DFT calculations ide...

Electrochemical stability is a critical performance parameter for the materials used as electrolytes and electrodes in batteries. Using first-principles electronic structure calculations, we have determined the electrochemical stability windows of magnesium binary and ternary spinel compounds. These materials are candidates for protective coatings,...

The full understanding of electrocatalytic reactions requires a complete knowledge of the elementary steps occurring in these reactions together with the corresponding rate constants as a function of the parameters controlling the electrochemical environment. Given the complexity of electrochemical electrode/electrolyte interfaces, the modeling of...

The full understanding of electrocatalytic reactions requires a complete knowledge of the elementary steps occurring in these reactions together with the corresponding rate constants as a function of the parameters controlling the electrochemical environment. Given the complexity of electrochemical electrode/electrolyte interfaces, the modelling of...

Employing density functional theory (DFT) calculations and x-ray photoelectron spectroscopy (XPS), we identify products of the reaction of the ionic liquid N,N - butylmethylpyrrolidinum bis(triuoromethylsulfonyl)imide (BMP-TFSI) with lithium in order to model the initial chemical processes contributing to the formation of the solid electrolyte inte...

Electrochemical stability is a critical performance parameter for the materials used as electrolytes and electrodes in batteries. Using first-principles electronic structure calculations, we have determined the electrochemical stability windows of magnesium binary and ternary spinel compounds. These materials are candidates for protective coating,...

Employing density functional theory (DFT) calculations and x-ray photoelectron spectroscopy (XPS), we identify products of the reaction of the ionic liquid N,N - butylmethylpyrrolidinum bis(trifluoromethylsulfonyl)imide (BMP-TFSI) with lithium in order to model the initial chemical processes contributing to the formation of the solid electrolyte in...

It is a general notion in interfacial electrochemistry that the stability of adsorbate phases that only contain hydrogen atoms should be independent of the pH value of the electrolyte on the scale of the reversible hydrogen electrode, whereas the stability of adsorbate phases that do not contain any hydrogen should be independent of the pH value on...

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. Curre...

This article reviews recent forays in theoretical modeling of the double layer structure at electrode/electrolyte interfaces by current atomistic and continuum approaches. We will briefly discuss progress in both approaches and present a perspective on how to better describe the electric double layer by combining the unique advantages of each metho...

It is a paradigm in chemistry that chemical reactions are mainly governed by thermodynamics. Within this assumption, reaction rates can be derived from transition state theory which requires a quasi-equilibrium between reactants and activated transition state complexes that is achieved through friction. However, to reach thermal equilibrium through...

The Cover Feature illustrates properties of the potential energy surface for charge carriers in spinel solid electrolyte and electrode materials that yield a descriptor for the ion mobility. The descriptor is based on the energetic difference between the two symmetrically different intercalation sites in these materials. This allows to predict the...

The prosperity and lifestyle of our society are very much governed by achievements in condensed matter physics, chemistry and materials science, because new products for sectors such as energy, the environment, health, mobility and information technology (IT) rely largely on improved or even new materials. Examples include solid-state lighting, tou...

It is a general notion in interfacial electrochemistry that the stability of adsorbate phases that only contain hydrogen atoms should be independent of the pH value of the electrolyte on the scale of the reversible hydrogen electrode, whereas the stability of adsorbate phases that do not contain any hydrogen should be independent of the pH value on...

Enabling high Mg ion mobility, spinel‐type materials are promising candidates for cathode or solid electrolyte applications. To elu‐ cidate the factors governing the observed high mobility of multivalent ions, periodic DFT calculations of various charge carriers (A = Li, Na, K, Mg, Ca, Zn and Al) in the ASc2 S4 and ASc2 Se4 spinel compounds were pe...

Alkali metal ion batteries, and in particular Li-ion batteries, have become a key technology for current and future energy storage, already nowadays powering many devices in our daily lives. Due to the inherent complexity of batteries and their components, the use of computational approaches on all length and timescales has been largely evolving in...

While the Mo 6 S 8 chevrel phase is frequently used as cathode material in Mg–ion batteries, theoretical studies on this material are comparatively scarce. The particular structure of the Mo 6 S 8 phase, with rather loosely connected cluster entities, points to the important role of dispersion forces in this material. However, so far this aspect ha...

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 th...

We report results of a combined experimental and computational model study on the interaction of the battery-relevant ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI) with a Mg thin film model electrode grown on a Ru(0001) substrate, which aims at a fundamental understanding of the solid electrolyte inter...

Ion mobility is a critical performance parameter not only in electrochemical energy storage and conversion but also in other electrochemical devices. On the basis of first-principles electronic structure calculations, we have derived a descriptor for the ion mobility in battery electrodes and solid electrolytes. This descriptor is entirely composed...

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 t...

It is a paradigm in chemistry that chemical reaction are mainly governed by thermodynamics. Within this assumption, reaction rates can be derived from transition state theory which requires a quasi-equilibrium between reactants and activated transition state complexes that is achieved through friction. However, to reach thermal equilibrium through...

Density functional theory calculations together with ab initio molecular dynamics (AIMD) simulations have been used to study the solvation, diffusion and transformation of Li+ and LiO2 upon O2 reduction in three organic electrolytes. These processes are critical for the performance of Li-air batteries. Apart from studying the structure of the solva...

Alkali metal ion batteries, and in particular Li-ion batteries, have become a key technology for current and future energy storage, already nowadays powering many devices of our daily lives. Due to the inherent complexity of batteries and their components, the use of computational approaches on all length and time scales has been largely evolving w...

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 base...

While the Mo6S8 chevrel phase is frequently used as cathode material in Mg--ion batteries, theoretical studies on this material are comparatively scarce. The particular structure of the Mo6S8 phase, with rather loosely connected cluster entities, points to the important role of dispersion forces in this material. However, so far this aspect has bee...

The surface structures of promising cathode materials for zinc-air batteries, Mn3O4 and Co3O4, have been systematically studied under operating conditions by density functional theory calculations. The environment has been taken into account using grand-canonical schemes both for gas-phase and electrochemical conditions. By analysing the structures...

The theoretical modeling of the double layer structure at electrode/electrolyte interfaces by current atomistic and continuum approaches is reviewed. We will briefly discuss recent progress in both approaches and present a perspective on how to better describe the electric double layer by exchanging the unique advantages of each method. First-princ...

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 phot...

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 th...

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 th...

Electrochemistry is concerned with processes at the interface between an electron conductor and an ion conductor. The reorganisation of electronic and ionic charge leads to the formation of two oppositely charged layers forming the so-called electric double layer (EDL). This chapter presents the results of molecular dynamics simulations that are ba...

The influence of electrolyte ions on the catalytic activity of electrode/electrolyte interfaces is a controversial topic for many electrocatalytic reactions. Herein, we focus on an effect that is usually neglected, namely, how the local reaction conditions are shaped by nonspecifically adsorbed cations. We scrutinize the oxygen evolution reaction (...

Nickel-based oxides are highly active, cost effective materials for the oxygen evolution reaction in alkaline conditions. Recent experimental studies have revealed the importance of surface deprotonation and alkali metal cation adsorption on the activity of Ni oxide surfaces, in contact with aqueous alkaline electrolyte. As a first step to elucidat...

Structures and processes at water/metal interfaces play an important technological role in electro-chemical energy conversion and storage, photoconversion, sensors or 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 to combine concepts from ch...

Batteries based on multivalent ions such as magnesium have been attracting considerable attention due to their potential for high energy densities, but their low ion mobility remains an obstacle. Herein, ionic conductivity in spinel host materials, which represent a promising class of cathode and solid‐electrolyte materials in batteries, is address...

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 phot...

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 phot...

Discrimination between electronic and structural effects in metal-support interactions (MSIs) is often hampered by contributions from either one. We report results of a combined experimental/theoretical study that directly demonstrate the action of electronic MSIs, while structural modifications like a partial overgrowth of metal nanoparticles by a...

Nickel-based oxides are highly active, cost effective materials for the oxygen evolution reaction in alkaline conditions. Recent experimental studies have revealed the importance of surface deprotonation and alkali metal cation adsorption on the activity of Ni oxide surfaces, in contact with aqueous alkaline electrolyte. As a first step to elucidat...