Track F
Designing Materials for Sustainable Energy Applications


Session F-1 Electrochemical energy systems (fuel cells, rechargeable batteries, supercapacitors; solar fuels)

F-1:IL01  Computer Modeling of Solid-state Batteries
V.I. YAMAKOV1, 2, Y. Lin2, A.A. Rains3, 4, J. Su2, J.H. Kang2, D.A. Dornbusch5, R.P. Viggiano5, 1Analytical Mechanics Associates, Hampton, VA, USA; 2NASA Langley Research Center, Hampton, VA, USA; 3NASA Interns, Fellows, and Scholars (NIFS) Program, NASA Langley Research Center, Hampton, VA, USA; 4University of Georgia, Athens, GA, USA; 5NASA Glenn Research Center, Cleveland, OH, USA

The need for safe, reliable, and compact high-capacity energy storage devices has led to increased interest in all-solid-state battery research. The use of solid electrolytes provides enhanced safety and durability due to their reduced flammability and increased mechanical strength. Computational modeling plays a substantial role in their design and development. A particle dynamics electromechanical model for simulating electrochemical processes in a solid-state battery cathode will be discussed. The model presents cathode microstructure at the particle level as a mixture of ionically conductive solid electrolyte particles, electrically conductive carbon additives, and cathodic reactant particles. After densification, the electric network connecting reactant particles with anodic and cathodic current collectors through the electrolyte and carbon particles is solved. Values of various key parameters, such as the overall conductivity of the cathode for lithium ions and electrons, and cathodic reactant material utilization are obtained. By representing the reactant particles as electrolyte or galvanic microcells, the overall performance of battery during charge or discharge processes can be predicted for a given powder composition.

F-1:L03  Microstructure Design of Polycrystalline Ceramics for Energy Applications
E. GARCIA, Purdue University, West Lafayette, IN, USA

By defining a thermodynamically consistent representation of materials that spatially resolves the multiphysical fields that results from formally considering microstructural features such as grain size, crystallographic texture, grain boundaries, particle size, and porosity, the time-dependent behavior is analyzed in materials for lithium-ion battery applications. Progress towards integrating the physical contributions of each individual phase and its processing-induced spatial distribution into advanced models is presented. The effect on the performance and degradations is analyzed. Reaches and limitations of well-known and emerging theories will be reviewed and compared, and efforts to accelerate to the limit of real time performance and degradation computations will be presented in an effort to explore the space of what is physically possible.

F-1:IL04  Accelerated Autonomous Exploration of Oxide Electrode Materials for High-temperature Electrolyzers and Fuel Cells
JAKE HUANG1, M. Papac2, D. FEBBA1, R. O'Hayre3, A. Zakutayev3, 1National Renewable Energy Laboratory, Golden, CO, USA; 2National Institute of Standards and Technology, Gaithersburg, MD, USA; 3Colorado School of Mines, Golden, CO, USA

The design of materials for electrochemical energy conversion is complicated by multifaceted property requirements like multi-carrier conductivity, stability, and catalytic activity. Time-consuming in-situ electrochemical characterization further hinders materials discovery efforts. Here, we illustrate a system for efficient screening of proton-conducting oxide electrodes for ceramic fuel cells and electrolyzers that utilizes combinatorial synthesis, accelerated impedance spectroscopy, and active learning. Combinatorial thin-film microelectrode libraries are fabricated via pulsed laser deposition (PLD) to enable high-throughput characterization in a half-cell configuration. A new “hybrid” impedance measurement technique provides an order-of-magnitude acceleration relative to conventional impedance spectroscopy (EIS). The distribution of relaxation times (DRT) is extracted from impedance to feed an active learning loop, which further reduces screening time with optimized experimental sequences. We apply this system to several combinatorial libraries to demonstrate both efficient pattern learning and optimization of expensive-to-evaluate properties like activation energy.

F-1:L05  Relation between Double Layer Structure, Capacitance and Surface Tension in Electrowetting of Graphene and Aqueous Electrolytes
Z. Wei, J.D. Elliott, A.A. Papaderakis, R.A.W. Dryfe, P. Carbone, Dept of Chemical Engineering, The University of Manchester, Manchester, UK; Diamond Light Source, Diamond House, Harwell Science and Innovation Park, Didcot, Oxfordshire, UK; Dept of Chemistry and Henry Royce Institute, The University of Manchester, Manchester, UK

Graphene, the building block for graphitic electrodes, is an ideal model for probing charge storage on a fundamental level. Herein, we investigate the thermodynamics of the graphene/aqueous electrolyte interface by utilizing a multiscale quantum/classical approach to provide insights into the effect of alkali metal ion (Li+) concentration on the interfacial tension (γ_SL) of the charged interface. We demonstrate that the dependence of γ_SL on the applied surface charge exhibits an asymmetric behaviour relative to the neutral surface. Changes in γ_SL greatly affect the total areal capacitance predicted by the Young-Lippmann equation but have negligible impact on the simulated total areal capacitance indicating that the EDL structure is not directly correlated with the wettability of the surface and different interfacial mechanisms drive the two phenomena. The proposed model is validated experimentally by studying the electrowetting response of highly oriented pyrolytic graphite. The approach developed herein introduces new conceptual routes for the investigation of wetting phenomena on carbon surfaces under potential bias.

F-1:L07  Solar Fuel from Photoelectrochemical Water Splitting: A Case Study of ZnO (Wurtzite) Single Crystals and Dense Thin Films
L. KAVAN1, H. KRYSOVA1, 2, V. MANSFELDOVA1, H. TARABKOVA1, A. PISARIKOVA2, Z. HUBICKA2, 1J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czech Republic; 2Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic

The n-ZnO (wurtzite) is a case material demonstrating fundamental limitations of (i) the classical Gärtner model of carrier dynamics in semiconductor photoanode and (ii) the Mott-Schottky analysis of its electronic structure. To address these problems, we prepared high-quality compact thin films by spray pyrolysis and by pulsed reactive magnetron sputtering combined with radio frequency electron cyclotron wave resonance plasma. The films were characterized by AFM, XRD, Kelvin probe, cyclic voltammetry, electrochemical impedance spectroscopy and photoelectrochemistry. The study of thin films is referenced, if relevant, to the (0001)-oriented single crystal with either Zn-face or O-face terminations. The Kelvin-probe measurements of the ZnO/air interface specifically distinguish the effects of calcination and UV-excitation, which are attributed to erasing of oxygen vacancies near the surface. The work functions at the electrochemical interface specifically address the growth protocol of the ZnO electrodes, but not the effects of crystallinity and calcination. Very high photocurrents of water oxidation are observed on the virgin films. The effect is discussed in terms of photocorrosion, and changes of work function by UV light.

Session F-2 Photovoltaics

F-2:IL01  First-principles Study of Defect Control in Thin Film Solar Cell
SU-HUAI WEI, Beijing Computational Science Research Center, Beijing, China

First-principles study of photovoltaic materials played an important role in developing solar cell technologies because it can provide useful physical insights, fresh perspectives, and new design principles for developing innovative solar cell materials with high solar power conversion efficiency and reduced cost. One of the most important issues in solar cell absorber materials is to control the defects, either for introducing charge carrier, improving charge transport, or reducing non-radiative carrier recombination. Thus, a good solar cell material should have good defect properties, that is, it can be easily doped such that sufficient charge carriers can be introduced to generate the required electric field and has less defect-induced recombination centers such that it has high carrier life time, so photo-generated charge can be collected. In this talk, using the thin-film solar cell absorber materials Cd(Te,Se) and Cu(In,Ga)Se2 as examples, I will discuss our recent study on how to select the best dopant in CdTe and understand the carrier recombination process in CIGS. Our study, therefore, provides theoretical guidelines to improve the solar cell performance in these technologies.

F-2:IL02  Understanding and Design of Photovoltaic and Energy Storage Materials
M. CHAN, Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL, USA

In materials and chemical science, the combination of high throughput computational modeling and experimentation has given rise to significant challenges and opportunities. Data science techniques such as machine learning, artificial intelligence, and computer vision have made a significant impact in the ease, scope, and speed of understanding of known materials and discovery of new ones. In this talk, we will discuss how we use data science approaches in conjunction with atomistic and first-principles modeling to interpret experimental characterization data (such as x-ray scattering, spectroscopy, scanning probe microscopy, and transmission electron microscopy) and carry out materials design (such as in zinc blende and hybrid perovskite optoelectronic materials).

F-2:L03  Accelerated Screening of Ternary Chalcogenides for Potential Photovoltaic Applications
TIANSHU LI, Department of Materials, Imperial College London, London, UK

Chalcogenides, which refer to chalcogen anions, have attracted considerable attention in multiple fields of applications. Compared to oxide counterparts, chalcogenides have demonstrated higher mobility and p-type dopability, owing to larger orbital overlaps between metal–X covalent chemical bondings and higher-energy valence bands derived by p-orbitals. Despite the potential of chalcogenides, the number of successfully synthesized compounds remains relatively low compared to that of oxides, suggesting the presence of numerous unexplored chalcogenides with fascinating physical characteristics. In this study, we implemented a systematic high-throughput computational screening on ternary chalcogenides using 34 crystal structure prototypes. We generated a material database containing over 400,000 compounds by exploiting the ion-substitution approach. The thermodynamic stabilities of the candidates were validated using the chalcogenides included in the OQMD. Furthermore, we theoretically evaluated the synthesizability and electronic structures of the stable candidates using accurate hybrid functionals. A series of in-depth characteristics, including the carrier effective masses, electronic configuration, and photovoltaic conversion efficiency, was also investigated.

F-2:IL06  Spin and Transient Delocalization Effects in Organic Semiconductors
D. BELJONNE, University of Mons, Mons, Belgium

We will present recent computational studies addressing the role of spin effects and transient delocalization of organic semiconductors. In the first part of the talk, we will review the results of a combined terahertz photoconductivity / fully atomistic non-adiabatic molecular dynamics simulations study of charge transport in two closely related molecular crystals. The emerging picture from that study is that of holes surfing on a dynamic manifold of vibrationally-dressed extended states with a temperature-dependent mobility that provides a sensitive fingerprint for the underlying density of states. We will discuss extension of the theory to highly-doped polymer semiconductors for use as active component in organic field effect and electrochemical transistors. In the second part of the talk, we will present a mechanistic investigation of spin conversion in organic semiconductors and discuss their implication for both photovoltaic and light-emitting diode applications.

F-2:IL07  Shift and Ballistic Currents from First Principles
Z. Dai, University of Texas, Austin, TX, USA; A.M. Schankler, A.M. Rappe, University of Pennsylvania, USA

As the need for clean and sustainable energy increases, renewed focus on alternative energy sources such as photovoltaics have become vital. This motivates study of the bulk photovoltaic effect (BPVE), a nonlinear optoelectronic property that can generate electricity without a p-n junction. To demonstrate the capability of first-principles BPVE theories to guide materials design, we outline an automated method to design distortions that enhance the shift current of monolayer MoS2 and use it to uncover a polar distortion that increases the integrated shift current more than ten-fold. Calculating the shift current contribution to the BPVE only explains part of the experimentally observed photocurrent. We present a method that enables the ballistic current-a current resulting from asymmetric scattering-from first principles. We calculate the ballistic current for BaTiO3 from first principles. The current due to electron-phonon scattering is comparable to the shift current, and is therefore experimentally relevant, while the current due to electron-hole scattering is much smaller in magnitude. This methodological development enables closer agreement between theory and experiments and lays the groundwork for further prediction and design of materials with large BPVE.

F-2:IL08  Selenium as a Top-cell Absorber for Tandem Photovoltaic- and PEC-cells
R. NIELSEN, T. Youngman, A. Azzar, A. Crovetto, B. Seger, H. Moustafa, S. Levcenco, H. Hempel, T. Olsen, O. Hansen, I. Chorkendorff, T. Unold, P.C.K. VESBORG, Technical University of Denmark, Kgs. Lyngby, Denmark

The ideal high-bandgap partner for a tandem solar absorber using c-Si as the low-bandgap bottom cell must have a bandgap of 1.6 eV to 1.9 eV and excellent optoelectronic properties. Selenium, perhaps the very first material to be studied for its photovoltaic properties, is emerging as an interesting candidate for this application. Indeed Se has a bandgap of around 1.95 eV [1] and a steep increase in absorption above this photon energy. Todorov et al showed [2] in 2017 that single-junction Se solar cells could reach 6.5% efficiency using a new cell architecture with a very thin absorber layer. Recently we have increased the OCV to a new record of 991 mV [2] and mapped the main shortfalls of state-of-the-art Se-cells preventing them from approaching their theoretical potential OCV. The talk will introduce Se as a solar absorber and discuss we know about its properties and progress towards use in solar devices such as tandem photovoltaics and PEC stacks [3].
[1] T. K. Todorov, et al, Nature Communications, 8, 682 (2017)
[2] R. Nielsen, et al , J. Mater. Chem. A, 10, 24199 (2022)
[3] R. Nielsen, et al. (submitted) "Monolithic Selenium/Silicon Tandem Solar Cells"

F-2:L10  Engineering of the Electronic Structure of Semi-conducting Oxides for Application in Li-ion and Li-sulfur Batteries
M. ZUKALOVA, M. Vinarcikova, B. Pitna Laskova, L. Kavan, J. Heyrovsky Institute of Physical Chemistry, Czech Acad. Sci, Prague, Czech Rep.; O. Porodko, M. Fabian, Institute of Geotechnics, Slovak Acad. Sci, Kosice, Slovak Rep.

Semiconducting oxides, e.g., TiO2 or, recently, high-entropy oxides represent materials with application potential in solar and fuel cells, photocatalysis, electrocatalysis, and batteries. Since their electronic and electrochemical properties are closely related to their structure, targeted synthetic procedures provide appropriate products for the particular application. In our work, we studied the effect of TiO2 additive in the composite cathode for Li-S batteries. Li-S batteries have received attention due to their high specific capacity of 1672 mAh g−1, however, their commercialization is hindered by the non-conductivity of S and Li2S and the redox shuttle between dissolved Li polysulfides. We found that the addition of nanocrystalline titanium dioxide to a cathode of Li-S cell enhances its voltammetric charge capacity by 19%. Titanium dioxide is active in the Li-S cell not only for the immobilization of polysulfides on the sulphiphilic surface but also due to its inherent electrochemical activity for sulfur reduction at potentials negative to Vfb. Analogously, the addition of a novel lithiated high-entropy oxychloride Li0.5(Zn0.25Mg0.25Co0.25Cu0.25)0.5Fe2O3.5Cl0.5 to the composite cathode in Li-S cell improved substantially its long-term electrochemical cycling stability.

Session F-3 Thermoelectrics

F-3:L03  Accelerated Discovery of Efficient Thermoelectric Materials Using a Novel Machine Learning Approach
S. Athar, N. Ramsahye, P. Jund, ICGM, Université de Montpellier, CNRS, Montpellier, France

Thermoelectric (TE) materials permitting the conversion of heat into electricity (and vice versa) are among the foremost sustainable energy solutions in the current context of a looming energy crisis. Their huge potential for energy harvesting is dependent upon discovering materials having higher TE efficiency than those available. But the vast chemical space of materials has only allowed for experimental/computational scanning of a small fraction till yet. Machine learning (ML) can enable this enormous scanning of the material space. However, the availability of small experimental TE datasets (at controlled conditions) severely limits application of many MLtechniques across different families of TE compounds. We propose to use a novel ML approach to predict physically informed descriptors from a relatively small dataset for three families of materials spanning the whole temperature range of interest. First very promising ML results for one family of compounds will be shown and have already been confirmed by DFT calculations. The best candidate materials emerging from these screenings will be finally synthesized after an initial verification of their TE properties and stability, using additional DFT calculations.

F-3:L04  Silicon Thermoelectrics for Energy Autonomous Integrated Circuits
m. lee, The University of Texas at Dallas, Richardson, TX, USA

Silicon integrated circuits (ICs) are the basis of internet-of-things (IoT) devices often embedded in inaccessible environments. Such electronics must be energy autonomous; they must carry an energy source on-chip or in-package. Microelectronic thermoelectric generators (µTEGs) are a possible energy autonomy solution where a thermal gradient exists. Current research on TE technology focuses on high TE figure-of-merit ZT materials. However, high ZT materials often contain toxic or non-earth-abundant elements and are usually incompatible with industrial Si IC fabrication. For decades Si itself was ignored for TE applications because of its poor ZT. However, our recent work on Si-based µTEGs, fabricated on a standard Si IC process line, show that these µTEGs can generate power per unit area per square of temperature difference ≥ 80 µWcm–2K–2, better than most Bi2Te3 TEGs. We have demonstrated that Si µTEGs as small as 0.2 mm2 can generate voltage and current sufficient to operate commercial IoT devices using heat sources ~20 °C above room temperature as the sole energy source. We will describe integration of a Si µTEG with a GaN power transistor to self-energize the transistor's management and control circuits using the waste heat generated by the power transistor itself.

Session F-4 Catalysts and catalytic processes for energy applications

F-4:IL02  DFT-CES: Eyes to See the Unseen, Buried Electric Double Layer
HYUNGJUN KIM, Department of Chemistry, KAIST, Daejeon, South Korea

Electrochemistry, the fundamental basis of sustainable energy conversion technologies, investigates the electric-chemical energy interconversion process at the electrode-electrolyte interface, where a characteristic liquid structure, namely an electric double layer (EDL) is known to be formed. Since the early 1900s, when the concept of EDL was theoretically formulated, unremitting efforts have been made to identify potential-dependent EDL structural changes, but only a few molecular details have been disclosed to date. To address this century-long debate by accurately modeling the electrified interface, we develop a first-principles-based multiscale method called a density functional theory in classical explicit solvents (DFT-CES), which mean-field couples the DFT and the molecular dynamics for respective description of electrode and electrolyte. Using DFT-CES, we find unprecedented liquid structural changes and phase transitions of the EDL. Atom-level investigation on the EDL region, enabled by our DFT-CES simulations, further unravels a new mechanistic role of the cations in the EDL during CO2 electroreduction. Our studies envisage a new perspective for developing better electrocatalysts by tailoring the electrochemical interface.

F-4:IL03  MOFs as Potential Heterogeneous Catalysts for Alkene Hydroformylation
YIFEI CHEN, L.T. Wang, H. Gong, M.H. Zhang, R & D Center for Petrochemical Technology, Tianjin University, China

Hydroformylation is one of the important homogeneous catalytic reactions in the chemical industry, whose product aldehydes are raw materials for several fine chemicals. In this work, the unsaturated metal nodes and tunable organic linkers in MOFs were utilized to design Rh-based heterogeneous catalysts. The catalytic performance and regulatory mechanism of 1-butene hydroformylation catalyzed by the designed Rh-based MOFs catalysts were investigated. In terms of the immobilization by nodes, the defective sites were constructed, which were used to anchor Rh metal for the construction of highly dispersed Rh/MOFs catalysts. The tunable effect of the electronegativity of nodal metal on catalytic performance of MOFs catalysts was investigated. 1Rh/MOF-5 catalyst with Zn as node showed the highest activity. In terms of the immobilization by ligands, the phosphine ligands were grafted onto the MOF-5 frameworks by post-synthesis method for the anchoring of Rh active sites. The effect of the content of phosphine ligands in MOFs on the electronic properties and the coordination environment of the Rh active sites. The effect of the content of phosphine ligands in MOFs on the electronic properties and the coordination environment of the Rh active sites was investigated.

F-4:IL04  Exploring Catalytic Reaction Networks with Machine Learning
K. REUTER, Fritz Haber Institute of the Max Planck Society Berlin, Germany

Chemical reaction networks form the heart of microkinetic models, which are one of the key tools available for gaining detailed mechanistic insight into heterogeneous catalytic processes. The exploration of complex chemical reaction networks is therefore a central task in current catalysis research. Unfortunately, microscopic experimental information about which elementary reaction steps are relevant to a given process is almost always sparse, making the inference of networks from experiments alone almost impossible. While first-principles computational approaches provide important complementary insights to this end, their predictions also come with substantial uncertainties related to the underlying approximations and, crucially, the use of idealized structure models. In this talk, I will review our approaches in this context, aiding both the inference of effective kinetic rate laws from experiment and the computational exploration of chemical reaction networks. We thereby aim at maximum agility and data efficiency, relying on active learning that only queries data on demand.


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