Office Of Basic Energy Sciences Research Articles

Development of Activity-Stability Descriptors for Transition Metal Oxide Electrocatalysis

The discovery of high-performing catalysts for the oxygen reduction and oxygen evolution reactions (ORR/OER) and related oxidative reactions is critical for the development of energy-efficient hydrogen fuel cells and electrolyzers. To achieve this goal, affordable and abundant alternatives to precious metal catalysts with sufficient stability and catalytic activity must be discovered. Ab-initio catalytic simulations combined with machine learning (ML) methods can play an important role in screening a larger search space of potential electrocatalysts materials of higher structural and compositional complexity, such as class of transition metal oxides (TMOs).In this talk, we will show how electronic and structural descriptors derived from bulk DFT calculations can improve ML models for the OER and ORR on transition metal oxides. In our previous work [1] we demonstrated that the electronic structure of the bulk TMOs, obtained as the crystal orbital Hamiltonian populations (COHP) of the metal-oxygen bond, is an accurate descriptor for O and OH adsorption. Here, we will discuss our extended model for O* and OH* adsorption across crystal structures and oxidation states, utilizing a new dataset of adsorption on binary (AxOy) oxide surfaces spanning the entire transition metal series. Building on our recent work, we extend the COHP-based model to a ML-based prediction of adsorption across multiple oxidation states to obtain a MAE < 0.2 eV for the O-OH and OH adsorption energy descriptors. These results can enable a more efficient screening of catalysts on the bulk level of DFT computation to significantly reduce the computational cost [2]. Furthermore, we will discuss how the COHP analysis can be directly applied to oxide surfaces to understand the impact of metal valency, structural reorganization, and magnetization on adsorption energetics [3]. Our prediction models of stability of bulk phases from COHP and oxidation state beyond binary alloys will also be highlited [4]. Lastly, we will discuss recent progress on collecting and accessing computational and underlying experimental data on catalysis-hub.org.This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis.[1] Comer, B. M., Li, J., Abild-Pedersen, F., Bajdich, M., Winther, K. T. (2022). Unraveling Electronic Trends in O∗ and OH∗ Surface Adsorption in the MO2Transition-Metal Oxide Series. , JPCC 2022 126 (18)(2022)[2] Comer, B. M., Bothra, .N, Lunger, J., Abild-Pedersen, F., Bajdich, M., Winther, K. T., Generalized Prediction of O and OH Adsorption on Transition Metal Oxide Surfaces from Bulk Descriptors (under review)[3] Bothra, .N, Comer, B. M., Winther, K. T., Bajdich, M., Understanding the Effects of Surface Bonding in Metal-Oxides Beyond the Limit of the Active Site (in preparation)[4] Craig, M. J., Kleuker, F., Bajdich, M., & Garcia-Melchor, M. (2023). FEFOS: A method to derive oxide formation energies from oxidation states. Catalysis Science & Technology.

Probing the Depths of Electrocatalysis Systems: X-Ray Absorption Spectroscopy Reveals Catalyst Behavior

X-ray absorption spectroscopy (XAS) is a powerful experimental technique used to study the electronic structure and local environment of atoms in a material. It provides valuable insights into the chemical bonding, oxidation states, and coordination geometry of elements. XAS has been widely applied in various fields of electrochemistry, including popular topics like the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and CO2 reduction reaction (CO2RR).Despite the growing recognition of the practical importance of XAS techniques, correlating experimental spectroscopy with the working mechanisms and deciphering the structure of the electrochemical interface under reaction conditions remains challenging. In the case of CO2RR, we utilized operando XAS to investigate multiple Cu-based catalysts in different cell configurations. Our findings revealed that altering the reaction environment can induce an alternative pathway for catalyst structural changes. Moreover, operando XAS demonstrated that the reduction of Cu oxide catalysts is not solely governed by applied potentials but is also influenced by mass transport and other parameters. For ORR, in situ XAS not only provides information about the local environment changes of Pt-based catalysts but also unveils surface properties through △μ-X-ray adsorption near-edge spectroscopy (△μ-XANES). This further aids in the discovery of degradation mechanisms in proton exchange membrane fuel cells (PEMFCs). In the case of HER, in situ XAS enables characterization beyond catalysts and extends to the electrochemical interface.Overall, XAS techniques play a crucial role in understanding the electronic structure and local environment of atoms in electrochemical systems, shedding light on reaction mechanisms and catalyst performance under realistic conditions Acknowledgement The authors thank the funding source from Liquid Sunlight Alliance under the U.S. DOE, Office of Science, Office of Basic Energy Sciences, Fuels Award Number DE-SC0021266 and the Laboratory Directed Research and Development Program of the Lawrence Berkeley National Laboratory under the U.S. DOE Contract No. DE-AC02-05CH11231.

Towards a Mechanistic Understanding of Transition-Metal Dissolution Phenomenon in Lithium-Ion Batteries

Dissolution of transition metals (TMs) from the layered NMC-type cathodes (LiNixMnyCozO2) occurs during cycling of lithium-ion full cells and is known to accelerate their capacity fade. This is because the dissolved metals migrate to the graphite anode and deposit there, where they accelerate irreversible active-lithium loss to reductive side reactions. The dissolution is known to get aggravated by cycling the cells to a greater upper cut-off voltage (UCV), where larger amounts of metals are typically found to be accumulated at the anode after long term cycling. At higher UCV oxygen loss from the cathode lattice also gets accelerated causing changes in the layered crystal structure at the surface level to a rock-salt and spinel mixture which has a very high impedance for Li-ion transport. Several other phenomena get accelerated as well, such as proton generation, and solvent decomposition etc. However, a complete mechanistic understanding of the how these phenomena impact the TM dissolution is lacking. For example, it is unclear whether the dissolution can occur in the charged state when the metals are in the oxidized state despite the presence of large number of acidic species, especially since most of the dissolved metal species typically detected in the electrolyte are in lower oxidation state. In this study, this question was targeted by aging the full graphite//NMC cells via long potentiostatic holds at UCV with/without any discharge steps, and recording the dissolved metals deposited at the graphite after aging. It is shown that a much greater amounts are deposited at the anode when discharge steps are included. Atomic structural changes from TM dissolution at the cathode surface corresponding to the two aging protocols in the charged/discharged state will also be presented.This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy (DOE) through Cathode-Electrolyte Interphase (CEI) Consortium. Part of the measurements was performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Insights into the Activity and Stability of Dual-Site Single Atom Catalysts for Oxygen Reduction Reaction Using a 2D Phthalocyanine-MOF

Hydrogen fuel cells have been considered as an effective strategy to shift fossil-fuel based economy to hydrogen economy. The performance of the fuel cells is often limited by the slow kinetics of the cathodic oxygen reduction reaction (ORR). Metal-organic frameworks (MOFs) based on 2D Phthalocyanine offer dual-site single atom catalyst (SAC) where M1 site typically amine coordinated node and M2 site is the phthalocyanine center (M1/M2 = Co, Cu, Ni). Here we conduct both computational studies and experimental measurements to elucidate the site selectivity and activity of two- and four-electron ORR process for pure (contains same element on both sites) and mixed (different M1 and M2) MOF system, and their overall stability. Using density functional theory (DFT), we find that regardless of site, Cobalt (Co) element shows better four-electron ORR activity than other elements in the mixed MOF system. Our integrated crystal orbital Hamilton population (ICOHP) calculations indicate that for pure MOF system, M1(d)-4N(2p) bonds are stronger than M2(d)-4N(2p), which raises d-band center of M2 sites closer to Fermi level, hence improves its activity towards four-electron ORR process. For mixed systems, M2 sites activity largely depends on the geometrical effects caused by M1 site elements. Our activity calculations reveal that Co (as M2) in the Ni-Co mixed MOF systems predicts lowest overpotential for ORR among all studied MOF system. Our dissolution mechanism and stability calculations show that Cu (as M1) causes stress/strain within the mixed MOF system denoting least stable among all studied during ORR process. In experiment, we found Co-based MOF, particularly Ni-Co demonstrates the highest kinetic activity and Cu is the least stable element, showing excellent agreement with computational studies. We hope this study will help in understanding the insight into the rational design of highly active and stable MOF for electrochemical processes. This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis.

(Invited) Ultrafast Spectroscopy of Nanostructured Plasmonic and Energy Conversion Materials

Ultrafast processes that occur upon the absorption of photons by a material frequently play important roles in the efficiency of a desired energy conversion or photocatalytic outcome. For example, energetic carriers produced upon photoexcitation of plasmonic systems can quickly dissipate energy through electron scattering processes on femtosecond timescales, followed by electron-phonon coupling on picosecond timescales. Once the carriers are thermalized, less energy is available to drive a charge separation or photocatalytic process. At the same time, there are number of handles with which to improve the efficiency of photoinduced processes, and ultrafast spectroscopy can be used to characterize that improvement. Nanostructuring, for example, can produce higher efficiency of photocatalytic processes as free charges are more likely to reach a surface following photoexcitation, and local anisotropies at the surface can drive electromagnetic field enhancements and the greater production of “hot” electrons. Hybridization of differing materials is also a powerful handle with which to manipulate or improve charge separation and photocatalytic outcomes. New materials can lead to greater robustness under illumination, as well as lead to changes in dissipation processes. In this talk, I describe recent efforts to characterize novel nanostructures of interest for plasmonics and energy conversion via ultrafast spectroscopy, as well as explore the ultrafast dissipation processes in refractory plasmonic nanomaterials. Particular attention is paid to dissipation of energy to the local environment of the nanoparticles as well as to ultrafast electron scattering processes. Hybrid nanostructures are also explored. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Investigation of Cu-Oxidation and Its Roles in Unassisted CO2 Reduction and Electrochemical Oxygen Evolution

Sunlight-driven photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructured catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu nanoparticle co-catalysts (p-GaN/Al2O3/Au/Cu) [1]. However, the exact oxidation state of Cu and the hole transfer directionality between Au and Cu remain under debate. Here, we combine computational and experimental efforts to investigate the different oxidation states of Cu under unassisted photocatalytic operating conditions. Experimentally we found that the Cu nanoparticles are primarily composed of Cu2O and CuO, CuCO3.Cu(OH)2 species, with no detectable metallic Cu present. The calculated bulk thermodynamics confirmed the high stability of CuCO3.Cu(OH)2 which is also validated by its largest contribution in the Pourbaix diagram, consistent with experimental observations. To gain insights into the origin of charge transfer, we simulate material interfaces namely, Au/CuO, Au/Cu2O, and Au/CuCO3.Cu(OH)2. Our theoretical analysis supports experimentally observed light-driven hole transfer from Au to Cu.More recently significant progress has been made in understanding copper oxide (CuO) behavior at oxidizing electrochemical conditions (> 1.5 V) [2]. In our study, we show CuO transforms into the OER active phase CuOOH, as evident in the bulk Pourbaix diagram presented here. Our calculations show a novel square planar, non-magnetic CuOOH phase. This discovery is supported by calculated Raman spectroscopic analysis, revealing distinct features corresponding to Cu3+ species at 567 and 585 cm-1, closely matching experimental peaks at 587 cm-1. These findings provide insights into the electrochemical properties of copper oxide phases and their relevance towards electrocatalytic OER. Acknowledgments:This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. Reference:[1] H. A. Atwater et al. ACS Energy Lett, 6, 1849 (2021)[2] M J. Janik et al. ACS Appl. Mater. Interfaces, 15, 27878 (2023)

PGM-Free Oxygen Evolution Reaction Catalyst for PEM Water Electrolysis – a Mechanistic Study on Activity and Durability for Practical Applications

Low temperature proton exchange membrane water electrolyzer (PEMWE) represents a critical technology for green hydrogen production. It offers the advantages of significantly higher current density and higher H2 purity, rendering it a preferred technology when high energy efficiency and low footprint are essential. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial demand to the electrode catalyst and the support. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place. At present, the platinum group metal (PGM) materials such as Ir black or Ir oxide are catalysts of choice. Their high cost and limited reserve add a significant cost barrier to PEM electrolyzer, which contributes to the overall expense of hydrogen production next only to the cost of electricity. Replacing Ir with earth-abundant transition metal oxides could help to reduce the electrolyzer system cost.For PEMWE application, a PGM-free anodic catalyst must be highly active to match the performance of Ir. Furthermore, it must be stable against oxidative acid corrosion. At Argonne National Laboratory, we recently developed a new PGM-free OER of a nanofibrous cobalt spinel catalyst co-doped with lanthanum and manganese (LMCF). [1] The catalyst was synthesized from the precursor of cobalt zeolitic methyl-imidazolate framework (Co-ZIF) doped with manganese and lanthanum. The Co-ZIF was mixed with a polymer solution and electrospun into nanofiber before being converted to fibrous cobalt spinel under low temperature oxidation to remove all the organics and carbon. The new PGM-free catalyst demonstrated a low overpotential of 353 mV (RHE) at 10 mA/cm2 and a low OER degradation over 360 hours in acidic electrolyte. A PEMWE containing this catalyst at its anode at ~2.0 mg/cm2 demonstrated a current density of 2000 mA/cm2 at 2.47 volts (Nafion® 115 membrane) or 4000 mA/cm2 at 3.00 volt (Nafion® 212 membrane). The membrane electrode was also subjected to accelerated-stress-test (AST) in both voltage cycling and galvanostatic run at different current densities. Low degradation rates under both ASTs were observed.In addition to catalyst design and synthesis, we also conducted extensive structural characterizations, stability measurement, as well as computational modeling. Our in situ study found that the OER process involves significant lattice oxygen movement, leading to lowering instead of raising the cobalt oxidation state during the electrolysis. The measurement of the stability number, combined with computational Pourbaix diagram, elucidated the importance of the operating potential in reducing catalyst dissolution. These findings offer in-depth understanding and direction of future development for PGM-free OER catalyst in PEM water electrolyzer. Acknowledgement: This work is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewal Energy, Hydrogen and Fuel Cell Technologies Office, and by Laboratory Directed Research and Development funding of Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DEAC02-06CH11357. Work performed at the Center for Nanoscale Materials and Advanced Photon Source, both U.S. Department of Energy Office of Science User Facilities, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.[1] “La- and Mn-doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis” Lina Chong, Guoping Gao, Jianguo Wen, Haixia Li, Haiping Xu, Zach Green, Joshua D. Sugar, A. Jeremy Kropf, Wenqian Xu, Xiao-Min Lin, Hui Xu, Lin-Wang Wang, Di-Jia Liu, Science 380, 609–616 (2023)

Dynamic systems modeling of the spallation neutron source cryogenic moderator system to optimize transient control and prepare for power upgrades

Through support of the US Department of Energy’s Office of Basic Energy Sciences, Oak Ridge National Laboratory has begun applying machine learning methods to improve accelerator and target performance of the Spallation Neutron Source (SNS). These methods are being applied to the control optimization and power upgrade of the SNS Cryogenic Moderator System (CMS). A numerical model of the CMS has been developed to study these optimizations and system modifications using EcosimPro. This paper compares steady-state and transient numerical results with experimental data. Control optimization studies focused on dampening mass flow, temperature, and pressure fluctuations during sudden losses of accelerator beam power. This analysis was conducted by adjusting five proportional-integral-derivative controllers connected to four flow control valves and one heater. Future efforts include power uprate studies focused on increasing the CMS cooling capacity. The current accelerator power is 1.4 MW; the first target station is being upgraded to 2.0 MW as part of the Proton Power Upgrade effort. The CMS cooling capacity is sufficient for 2.0 MW operation.

Phonon dispersion at long and short wavelength as seen by ultrasound and neutron spectroscopy

Lattice excitations are fundamental energy carriers responsible for thermal transport in every solid. Whereas ultrasound spectroscopy typically probes these excitations in the kHz to MHz “sound” regime corresponding to mm to μm wavelengths, inelastic scattering of neutrons or x-rays probe the THz regime and Å wavelength. We will discuss a few examples of materials with peculiar sound and phonon properties, such as chiral α-TeO;2 and the AgSbTe;2-PbTe (LAST) solid solution. Analysis of resonant ultrasound data of α-TeO;2 requires the use of code that supports chiral space groups, such a RUSCal; intriguingly sound is extremely anisotropic, and in some directions the speed of sound is highly frequency dependent in the 0–1 THz range. LAST exhibits nanoscale inhomogeneities where the speed of sound is different in the matrix and the nanoinclusions. Work supported by the US Department of Energy (DOE), Office of Basic Energy Science (BES), and by Laboratory Directed Research at Oak Ridge National Laboratory; this research used resources at the Spallation Neutron Source a facility supported by DOE, BES, Scientific User Facilities Division. J. Torres, A. Flores-Bettancourt, M. Manley, B. Winn, G. Yumnam, I. Sergeev, P. Bauer-Pereira and A. Jafari are gratefully acknowledged for their collaboration.

Probing the Effect of Environments on the Stability of Ni2P Nanoparticle Electrocatalysts

Ni2P has been shown to be an effective catalyst for the hydrogen evolution reaction (HER), making it a promising replacement for Pt which is the current state of the art HER catalyst.1,2 H2 is a clean-energy critical fuel and chemical highlighted by the US Department of Energy’s “Hydrogen Shot,” which seeks to reduce “the cost of carbon-neutral hydrogen by 80% to $1 per 1 kg in 1 decade, highlighting the key role of hydrogen in implementing carbon-neutral solutions.”3 Ni2P is also a good or promising catalyst for other reactions, such as alcohol oxidation, hydrodesulfurization,4,5 nitrate reduction, and oxygen evolution reaction.6 However, Ni2P and other TMPs are susceptible to oxidation, which can lead to catalyst degradation and loss in certain conditions.7,8 Stability is an important part of catalysis, especially for achieving the goals of the Hydrogen Shot. Therefore, it is important to understand complex degradation mechanisms in order to better understand structure-activity relationships in these materials. In the present work, in situ Ni K-edge X-ray absorption spectroscopy (XAS) and ex situ P Kα and Kβ X-ray emission spectroscopy (XES) couple together to understand the degradation of Ni2P and show the effects of electrolyte pH, ligands, and air on Ni2P nanoparticles.5 nm Ni2P nanoparticles were synthesized by heating NiCl2 and tris(diethylamino)phosphine in oleylamine. The nanoparticles were drop cast onto carbon fiber paper electrodes and Si wafers or Au-coated wafers for P Kα and Kβ XES. Oleylamine ligands are removed by thermal annealing. Electrochemical experiments were conducted with a three-electrode cell using carbon fiber paper or Au-coated wafers deposited with Ni2P nanoparticles as working electrode, Ag/AgCl calibrated to the H2 redox couple as reference electrode, and graphite rod as counter electrode. P Kα and Kβ XES experiments were conducted inside a N2 glovebox to prevent unintentional air oxidation. Transmission-mode Ni K-edge XAS was conducted on a benchtop spectrometer.Upon exposure to air, as-synthesized Ni2P nanoparticles were studied via P Kα and Kβ XES. Results showed that the phosphide species converted to phosphate with analysis of intermediates well fit by a simple two-phase mixture. Phosphide:phosphate ratios were quantified using linear combination analysis, providing a powerful tool to analyze P speciation on various samples in an inert environment and with minimal loss of material, both advantages of this system over 31P magic angle spinning solid state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. Continued work looks at analyzing the effects of the ligand environment on the stability of nanoparticles in electrolytes spanning from acidic to basic pH. We hypothesize that ligands will significantly stabilize the nanoparticles against corrosion and that without ligands Ni2P readily converts to a nickel phosphate species upon exposure to electrolyte.References(1) Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135 (25), 9267–9270. https://doi.org/10.1021/ja403440e.(2) Liu, P.; Rodriguez, J. A. Catalysts for Hydrogen Evolution from the [NiFe] Hydrogenase to the Ni2P(001) Surface: The Importance of Ensemble Effect. J. Am. Chem. Soc. 2005, 127 (42), 14871–14878. https://doi.org/10.1021/ja0540019.(3) Bullock, M.; More, K. Basic Energy Sciences Roundtable: Foundational Science for Carbon-Neutral Hydrogen Technologies (Report); DOESC Office of Basic Energy Sciences, 2022. https://doi.org/10.2172/1834317.(4) Layan Savithra, G. H.; Muthuswamy, E.; Bowker, R. H.; Carrillo, B. A.; Bussell, M. E.; Brock, S. L. Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering. Chem. Mater. 2013, 25 (6), 825–833. https://doi.org/10.1021/cm302680j.(5) Rodriguez, J. A.; Kim, J.-Y.; Hanson, J. C.; Sawhill, S. J.; Bussell, M. E. Physical and Chemical Properties of MoP, Ni2P, and MoNiP Hydrodesulfurization Catalysts: Time-Resolved X-Ray Diffraction, Density Functional, and Hydrodesulfurization Activity Studies. J. Phys. Chem. B 2003, 107 (26), 6276–6285. https://doi.org/10.1021/jp022639q.(6) Menezes, P. W.; Indra, A.; Das, C.; Walter, C.; Göbel, C.; Gutkin, V.; Schmeiβer, D.; Driess, M. Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting. ACS Catal. 2017, 7 (1), 103–109. https://doi.org/10.1021/acscatal.6b02666.(7) Ha, D.-H.; Han, B.; Risch, M.; Giordano, L.; Yao, K. P. C.; Karayaylali, P.; Shao-Horn, Y. Activity and Stability of Cobalt Phosphides for Hydrogen Evolution upon Water Splitting. Nano Energy 2016, 29, 37–45. https://doi.org/10.1016/j.nanoen.2016.04.034.(8) Parra-Puerto, A.; Ng, K. L.; Fahy, K.; Goode, A. E.; Ryan, M. P.; Kucernak, A. Supported Transition Metal Phosphides: Activity Survey for HER, ORR, OER, and Corrosion Resistance in Acid and Alkaline Electrolytes. ACS Catal. 2019, 11515–11529. https://doi.org/10.1021/acscatal.9b03359.

(Invited) Exploring Solar-Driven CO2 Reduction to C2+ Products

Use of solar irradiance to drive CO2 reduction (CO2R) holds great promise for the sustainable generation of energy-dense fuels and chemicals, especially as it relates well to carbon capture technology. Multicarbon (C2+) products (e.g., ethylene, ethanol, propanol) are particularly attractive because they have a large market size and can be further converted to higher molecular weight hydrocarbons fuels that have high volumetric and mass energy densities. Metallic copper (Cu) has the unique ability to catalyze CO2 to C2+ products with high faradaic efficiency; however, the product distribution of CO2R on Cu is potential and microenvironment dependent. In this talk, we will explore CO2R via different routes using both experiments and simulation. We will focus on obtaining C2+ products via tailoring the microenvironments including the use of ionomer films that are quite effective at the lower current densities that match against the solar irradiance. We will demonstrate how control of the local environment and dynamic operation provide metastable states of high pH and high CO2 concentration, thereby enabling high CO2R to C2+ production.In addition, for direct photoelectrochemical CO2R, there is an optimum cell design and operating photovoltage that is not at the maximum power point (unlike water splitting) due to the selectivity dependence on potential. Using a continuum model of PEC CO2R, we will explore the co-design of the photoelectrode bandgaps and device architecture for the generation of C2+ products. The simulation results demonstrate the critical importance of simultaneously engineering the photoelectrode and device design and operation in order to ensure the photovoltage and photocurrent from the photoelectrode enables operation at the optimum potential. Finally, for PEC CO2R, we will explore the use of metal-insulator-semiconductor (MIS) structures to obtain high rates of CO2R. This includes both theoretical and experimental investigations that elucidate the controlling phenomena and when coupled with the ionomer films provide high rates of direct PEC CO2R. Overall, the insights between the photoelectrode and device design is critical for the design of monolithic, unassisted PEC CO2R systems that yield high STC2+ efficiency.AcknowledgementsThis material is based partially on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266 and a University of California grant.

Predictive models of long COVID

The cause and symptoms of long COVID are poorly understood. It is challenging to predict whether a given COVID-19 patient will develop long COVID in the future. We used electronic health record (EHR) data from the National COVID Cohort Collaborative to predict the incidence of long COVID. We trained two machine learning (ML) models - logistic regression (LR) and random forest (RF). Features used to train predictors included symptoms and drugs ordered during acute infection, measures of COVID-19 treatment, pre-COVID comorbidities, and demographic information. We assigned the 'long COVID' label to patients diagnosed with the U09.9 ICD10-CM code. The cohorts included patients with (a) EHRs reported from data partners using U09.9 ICD10-CM code and (b) at least one EHR in each feature category. We analysed three cohorts: all patients (n=2,190,579; diagnosed with long COVID=17,036), inpatients (149,319; 3,295), and outpatients (2,041,260; 13,741). LR and RF models yielded median AUROC of 0.76 and 0.75, respectively. Ablation study revealed that drugs had the highest influence on the prediction task. The SHAP method identified age, gender, cough, fatigue, albuterol, obesity, diabetes, and chronic lung disease as explanatory features. Models trained on data from one N3C partner and tested on data from the other partners had average AUROC of 0.75. ML-based classification using EHR information from the acute infection period is effective in predicting long COVID. SHAP methods identified important features for prediction. Cross-site analysis demonstrated the generalizability of the proposed methodology. NCATS U24 TR002306, NCATS UL1 TR003015, Axle Informatics Subcontract: NCATS-P00438-B, NIH/NIDDK/OD, PSR2015-1720GVALE_01, G43C22001320007, and Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy Contract No. DE-AC02-05CH11231.

(Invited) Dynamics of Light-Matter Interactions in Plasmonic Optical Cavities for Characterizing Nanostructures Relevant to Energy Conversion and Photocatalysis

Optical cavities are an established means to increase light-matter interactions with a wide range molecules, nanostructures and bulk materials. The use of an optical cavity to increase the likelihood of photon absorption by a material has clear potential for being of value for optical energy conversion and photocatalysis. Furthermore, optical cavities can significantly alter excited state dynamics due to the potential for Purcell effects that increase radiative rates of emission of a given material, molecule, or nanostructure. These dynamic changes can serve as a sensing mechanism of cavity impact to photoprocesses, making characterization tools such as transient absorption and time-resolved emission measurements an effective means to probe the degree of light-matter coupling. Taken a step further, these characterization tools can help establish the degree of light-matter coupling necessary to control excited state lifetimes for a particular purpose or application. Here, we explore the dynamics of nanostructured systems coupled to, or made out of, plasmonic materials. Importantly, plasmonic structures are well-known to serve as a type of optical cavity, and though plasmonic cavities are lossier than their dielectric counterparts, they can also confine light to a small mode volume which is very helpful for increasing photonic interactions with nanostructures. The focus of this talk is on materials and nanostructures of interest for solar energy conversion or photocatalysis, such plasmonic nanoparticles and semiconducting nanoparticles, which are interacting with or functioning as, a plasmonic cavity. The plasmonic cavity can be as simple as a thin metal film that supports a propagating surface plasmon polariton (SPP). We also explore refractory plasmonic systems due to their potential durability and reduced likelihood of melting under optical illumination as compared to noble metal nanostructures. The dynamics of nanostructure photoprocesses as a function of photon energy relative to the cavity resonance is explored in detail and impact on applications is described. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

(General Student Poster Award Winner - 2nd Place) Electrochemical Routes for Polymer Upcycling

Approximately 380 million tons of plastic are produced annually, and it is projected to rise to nearly 1.1 billion by 2050 [1]. The largest fraction of such waste consists of polyethylene (PE) and polypropylene (PP), which commonly require energy-intensive methods to achieve depolymerization (such as pyrolysis and hydrogenolysis) due to their remarkable thermodynamic stability. Electrochemical methods are a promising alternative for polymer upcycling as they can utilize renewable energy to create an external potential, overcoming the thermodynamic constraints that the C-C bond cleavage endothermicity imposes on low-temperature polymer conversion. They also offer improved chemical process control by manipulating the electrode potential and minimizing the use and storage of hazardous reagents. Electrochemistry provides a broad range of opportunities for establishing green routes to converting plastic into valuable products.Botte's group is investigating electrochemical approaches to convert polyolefins into valuable products like fuels and fatty acids [2]. Our findings indicate that an electrocatalyst in concert with controlled ionic strength and applied potential enable the selective functionalization of polyolefins and their defragmentation towards target molecules regardless of impurities present in the polymer. In this presentation, we will discuss results of the electrochemical functionalization and deconstruction of low-density polyethylene implementing transition metal electrocatalysts. Acknowledgments: The authors would like to acknowledge the financial support of the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Upcycling of Polymers Program, under Award DE-SC0022307[1] J. E. Rorrer, C. Troyano-Valls, G. T. Beckham, and Y. Román-Leshkov, "Hydrogenolysis of Polypropylene and Mixed Polyolefin Plastic Waste over Ru/C to Produce Liquid Alkanes," ACS Sustainable Chemistry & Engineering, vol. 9, no. 35, pp. 11661-11666, 2021/09/06 2021, doi: 10.1021/acssuschemeng.1c03786.[2] G. G. Botte, "Process for the Electrochemical Up-Cycling of Plastics (US Pending Patent)," U.S. Patent 63040929, 2020.

Computational Search for a Descriptor of Electrocatalysis in Transition Metal-Oxides

Currently, the most effective electrocatalysts for oxygen reduction (ORR) and oxygen evolution reactions (OER) are comprised of noble metal oxides, which bring issues of high cost and scarcity. Discovering earth-abundant alternatives is challenging due to the costly and time-consuming experiments. High-throughput atomistic simulation of catalysts can be an efficient route for enabling the better design and discovery of new electrocatalysts. The efficient use of this approach relies on an activity descriptor that can capture the qualitative and quantitative catalytic trends. In the past, multiple descriptors based on electronic properties have been proposed either reaction-specific or system specific. Therefore, we need a descriptor, which can capture the bonding strength accurately for any sort of reaction or system.In this work, we study the trends of O*/OH* adsorption energies for a wide range of pure metal oxide polymorphs[1] namely rocksalt (MO), corundum (M2O3), rutile (MO2), pentoxide (M2O5) and MO3 in all conceivable oxidation states i.e., +2, +3, +4, +5 and +6 respectively. The main drivers of the adsorption energy are the extent of filling of the bonding and anti-bonding orbitals, along with the spin-dependent coupling strength between the metal-d and oxygen-2p atomic orbitals. This property can be easily captured with the help of crystal orbital Hamiltonian population (COHP). We have observed a strong correlation between the integrated COHP I(COHP) of the bulk system and the adsorption energy, which indicates expensive surface-level electronic calculations can be replaced by bulk-level computations. However, this correlation does not hold on two classes of systems: (i) d0 systems and (ii) systems with significant surface distortion during the reaction. We have considered a different approach to address these systems, where instead of a single bond ICOHP, we account for the summation of the ICOHP around the active site.In search of promising catalysts, we also report tetrahedral systems for 3d, 4d and 5d transition metal oxides, i.e., zinc blende, wurtzite and square planar systems. This will broaden the horizon of possible catalysts along the octahedral systems. We correlate the bulk ICOHP with the surface reactivity of these systems, which highlights the applicability of ICOHP as a universal descriptor across a series of metal oxide systems and guide the design of novel catalysts.This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis.[1] "Unravelling Electronic Trends in O* and OH* Surface Adsorption in the MO2 Transition-Meta Oxide Series"; Benjamin M. Comer, Jiang Li, Frank Abild-Pedersen, Michal Bajdich, Kirsten Winther, 2022, (ACS J. Phys. Chem C.,)[2] “Predicting O* and OH* Surface Adsorption on Transition Metal Oxides from Bulk Structure”; Benjamin M. Comer, Neha Bothra, Jaclyn Lunger, Frank Abild-Pedersen, Michal Bajdich, Kirsten Winther, Manuscript under preparation.

Photo-Electrochemical Oxygen Evolution Activity in Nickel and Cobalt Antimonates

Renewable generation of fuels via solar energy offers promising pathways towards sustainable energy future. Its deployment hinges on the discovery of electrochemically durable materials with good solar-to-chemical conversion efficiency. Necessary visible spectrum photoresponse from electrochemically stable materials is however quite rare. On the other hand, the oxygen evolution reaction (OER) requires electrodes that are not only catalytically active, but also stable under harsh electrochemical environments. In this talk, we report on and theoretical understanding of photo-electrochemical behavior an amorphous and crystaline versions of Ni-Sb-Ox and Co-Sb-Ox oxide photoanodes discovered via high-throughput experimental screening [1,2]. The newly discovered amorphous phases meet the requirements of operational stability, visible photoresponse, and appreciable photovoltage. Guided by experimental X-ray absorption characterization of these systems we use density functional theory calculations to perform a prototype phase search to identify a broad family of stable and metastable mixed rutile and hexagonal-like phases for other compositions [3]. Detailed Pourbaix analysis of the identified phases show excellent electrochemical stability, consistent with experimentally measured electrolyte concentrations of photoelectrochemical cells. We analyze when he identified phases form favorable oxygen vacancies formation energies under the reducing synthesis conditions which match measured Ni K-edge x-ray absorption spectra. The calculated OER overpotentials for the most active sites decreases with increasing Ni/Co content, which captures the experimentally observed trend. Stable amorphous metal-antimonates photoanodes are important systems for computational understanding of both the structural and catalytic behavior of these complex oxides and elucidating the co-optimization of photo-electrochemical activity and durability. This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under award DE-SC0021266.[1] Zhou, L., Peterson, E. A., Rao, K. K., Lu, Y., Li, X., Lai, Y., Bauers, S. R., Richter, M. H., Kan, K., Wang, Y., Newhouse, P. F., Yano, J., Neaton, J. B., Bajdich, M., & Gregoire, J. M. Addressing solar photochemistry durability with an amorphous nickel antimonate photoanode. Cell Reports Physical Science, 3(7), 100959. (2022).[2] Zhou, L., Wang, Y., Kan, K., Lucana, D. M., Guevarra, D., Lai, Y., & Gregoire, J. M. Surveying Metal Antimonate Photoanodes for Solar Fuel Generation. ACS Sustainable Chemistry and Engineering, 21, 33. (2022).[3] Rao, K. K., Zhou, L., Lai, Y., Richter, M. H., Li, X., Lu, Y., Yano, J., Gregoire, J. M. Bajdich, M., Resolving Atomistic Structure and Oxygen Evolution Activity in Nickel Antimonates, (under review).

Walking the 'design-build-test-learn' cycle: flux analysis and genetic engineering reveal the pliability of plant central metabolism.

This article is a Commentary on Morley et al. (2023), 239: 1834–1851.

How Halide Sub-Lattice Affects Li Ion Transport in Antiperovskites

Li-based antiperovskites (LiAP, Li3-x OH x X, X = Cl, Br) are an emergent class of Li-ion conductors that are potential candidates for electrolytes in all-solid-state batteries. As a material class, pLiAP shows vast compositional design freedom; however, the resulting properties are susceptible to synthesis and processing methodologies. For example, proton incorporation and halide mixing stabilize the perovskite cubic phase near room temperature, and halides mixtures near the eutectic points drive the solid-state reaction temperature down, allowing for faster synthesis and processing conditions (< 1 h). The mixed halogen compositions, such as Li2OHCl0.37Br0.63, also show a 30-fold improvement in room temperature ionic conductivity of a single halide structure, 1.5 x 10-6 vs. 4.9 x 10-8 S cm-1 (Li2OHCl). Despite the growing interest in these materials, important questions remain about LiAPs on the structure-property correlation upon halide substitution and the correlations between the OH/halide dynamics and the Li-ion transport. We thus attempted to deconvolute how proton dynamics and halide substitution enhance or impede ionic conduction in pLiAP at compositions near the halide salts' eutectic points.We combined infrared spectroscopy and nuclear magnetic resonance (NMR) with first-principles density functional theory (DFT) calculations to deconvolute halide mixing effects from local proton dynamics on Li-ion transport. The NMR results and ab initio molecular dynamics suggest that Li+ transport is more strongly correlated with halide dynamics. While the hydroxide does stabilize the highly conductive cubic structure, it limits correlative ionic transport and thus lowers Li+ conductivity.Experiment design, data analysis, and manuscript preparation (RLS) were supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering. Synthesis (THB and JN) were supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program. P. J. acknowledges partial support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-96ER45579. H. F. was supported from U.S. Department of Energy (Award No. DE-EE0008865). This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The NMR characterization part of the work is supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, and Basic Energy Sciences. The NMR work was performed at the W. R. Wiley Environmental Molecular Sciences Laboratory, a DOE User Facility sponsored by the Office of Biological and Environmental Research, located at Pacific Northwest National Laboratory. Figure 1

Probing Local Ion Insertion through Strain-Current Correlation

Among different electrochemical energy storage devices, the ones that store a higher amount of energy (e.g., batteries) often undergo larger ion insertion-induced structural transformation and volume change, which results in lower rate performance. The ones that store a lower amount of energy (e.g., supercapacitors) usually show gradual structural change and smaller volume change. There is a strong correlation between electrochemistry and mechanical properties. Understanding the electro-chemo-mechanical coupling and controlling the ion insertion-induced strain is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local volume changes and other mechanical responses sub-nanometer spatial resolution under the conditions close to the device operationIn this work, we monitored electrode volume change via in-situ AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite and MXene) with the increasing complexity of current-deformation relationships.The work was supported by the Fluid Interface Reactions, Structures, and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Li Morphology Evolution during Initial Cycling in a Gel Composite Electrolyte

Li metal anodes are the potential solution for high-energy batteries. One of the challenges of applying such a high-energy anode is Li dendrite growth, which results in short-circuit and thermal runaway. Current battery research focuses on developing solid electrolytes to serve as a physical barrier to prevent dendrite growth. However, the Li morphology change during plating and stripping, and the mechanisms of how Li dendrite grows and propagates into a complex composite solid electrolyte are poorly understood. Understanding and controlling Li morphology evolution, dendrite formation, and growth during cycling are crucial to developing dendrite suppression strategies for solid electrolytes and enabling high-energy lithium metal batteries.In this work, Li morphology evolution during initial cycling in a crosslinked PEO-based gel composite electrolyte full cell with NMC 811 cathode is monitored via post-mortem SEM. The results show that severe surface pitting occurs as early as the second stripping cycle. Pit formation and continuous dissolution is the main cause of Li surface roughening and dendrite growth mechanism in the model gel composite electrolyte. Comparing Li dendrite growth mechanisms in liquid, polymer, and solid electrolytes, the observed dendrite growth mechanism resembles that of the liquid electrolyte the most. This study suggests that strategies to improve the electrochemical reversibility of electrodeposited Li reported in liquid electrolytes to control Li morphology and prevent dendrite growth may be transferrable in a gel electrolyte.This work is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. Part of the measurements was performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.