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Jaramillo, Thomas F.

Publications and source records attributed to Jaramillo, Thomas F..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Dynamics of precatalyst conversion and iron incorporation in nickel-based alkaline oxygen evolution reaction catalysts

The efficiency of alkaline water electrolyzers is limited by the oxygen evolution reaction (OER). The design of improved OER catalysts requires understanding of material changes induced by the electrolyte under oxidizing potentials. We compare four Ni-based thin-film precatalysts—Ni, NiO, Ni(OH) 2 , and NiS x —in 0.1 M KOH with and without Fe impurities. Precatalyst conversion to the active oxyhydroxide catalysts and their OER performance are induced and followed using cyclic voltammetry. Without Fe electrolyte impurities, the precatalysts convert at different rates to a similar, modestly active NiOOH catalyst. Added Fe impurities are incorporated concurrently with the oxyhydroxide formation leading to active Ni 1-x Fe x OOH catalysts. The NiS x and Ni(OH) 2 precatalysts rapidly convert to oxyhydroxides both with and without Fe, while conversion of Ni and especially NiO is slowed down by Fe impurities. Choice of the precatalyst and presence of Fe impurities are key factors in designing active Ni 1-x Fe x OOH OER catalysts for electrolyzers.

alkaline electrolysis↗
DOE OSTI2024

Electrodialysis and nitrate reduction (EDNR) to enable distributed ammonia manufacturing from wastewaters

Underutilized wastewaters containing dilute levels of reactive nitrogen (Nr) can help rebalance the nitrogen cycle. This study describes electrodialysis and nitrate reduction (EDNR), a reactive electrochemical separation architecture that combines catalysis and separations to remediate nitrate and ammonium-polluted wastewaters while recovering ammonia. By engineering operating parameters (e.g., background electrolyte, applied potential, electrolyte flow rate), we achieved high recovery and conversion of Nr in both simulated and real wastewaters. The EDNR process demonstrated long-term robustness and up-concentration that recovered >100 mM ammonium fertilizer solution from agricultural runoff that contained 8.2 mM Nr. EDNR is the first reported process to our knowledge that remediates dilute real wastewater and recovers ammonia from multiple Nr pollutants, with an energy consumption (245 MJ per kg NH 3 –N in simulated wastewater, 920 MJ per kg NH 3 –N in agricultural runoff) on par with the state-of-the-art. Demonstrated first at proof-of-concept and engineered to technology readiness level (TRL) 4–5, EDNR shows great promise for distributed wastewater treatment and sustainable ammonia manufacturing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Addressing challenges for operating electrochemical solar fuels technologies under variable and diurnal conditions

The outdoor operation of electrochemical solar fuels devices must contend with challenges presented by the cycles of solar irradiance, temperature, and other meteorological factors. Herein, we discuss challenges associated with these fluctuations presented over three timescales, including the effects of diurnal cycling over the course of many days, a single diurnal cycle over the course of hours, and meteorological phenomena that cause fluctuations on the order of seconds to minutes. We also highlight both reaction-independent and reaction-specific effects of variable conditions for the hydrogen evolution reaction and CO 2 reduction reaction. We identify key areas of research for advancing the outdoor operation of solar fuels technology and highlight the need for metrics and benchmarks to enable the comparison of diurnal studies across systems and geographical locations.

08 HYDROGEN↗
DOE OSTI2024

CO 2 Conversion to Butene via a Tandem Photovoltaic–Electrochemical/Photothermocatalytic Process: A Co-design Approach to Coupled Microenvironments

Here, we developed a tandem, unassisted, solar-driven electrochemical and photothermocatalytic process for the single-pass conversion of CO 2 to butene using only simulated solar irradiation as the energetic input. The two-step process involves electrochemical CO 2 reduction (CO 2 R) to ethylene followed by ethylene dimerization to butene. We assessed two unassisted electrochemical setups to concentrate ethylene in the CO 2 R reactor, achieving concentrations up to 5.4 vol.% with 1.8% average solar-to-ethylene conversion and 5.6% average CO 2 -to-ethylene single-pass conversion under 1-sun illumination. When passed through the photothermocatalytic ethylene oligomerization reactor, we generated 600 ppm of butene under 3-sun illumination. Through analysis of this process, we identified that the presence of H 2 , CO, and H 2 O leads to rapid deactivation of the Ni-based ethylene oligomerization catalyst.

14 SOLAR ENERGY↗
DOE OSTI2024

Modeling Diurnal and Annual Ethylene Generation from Solar-Driven Electrochemical CO 2 Reduction Devices

Integrated solar fuels devices for CO 2 reduction (CO 2 R) are a promising technology class towards achieving net-negative carbon emissions. Designing integrated CO 2 R solar fuels devices requires careful co-design of electrochemical and photovoltaic components as well as consideration of the diurnal and seasonal effects of solar irradiance, temperature, and other meteorological factors expected for ‘on-sun’ deployment. Here, using a photovoltaic-electrochemical (PV-EC) platform, we developed a temperature and potential-dependent diurnal and annual model using experimental CO 2 R performance of Cu-based electrocatalysts, local meteorological data from the National Solar Radiation Database (NSRD), and modeled performance of commercial c-Si PVs. We simulated diurnal product outputs with and without the effects of ambient temperature to determine gaseous product temperature sensitivity. From these outputs, we observed seasonal variation in gaseous product generation, with up to two-fold increases in ethylene productivity between the Winter and Summer, analyzed the consequences of dynamic cloud coverage, and identified periods where device cooling/heating mechanisms could be implemented to maximize ethylene generation. Finally, we modeled the annual ethylene generation for a scaled 1 MW solar farm at three different locations (Beijing, CN; Sydney, AUS; Barstow, CA) to determine the consequences of local meteorological climates on PV-EC CO 2 R product output, recording a maximum ethylene output of 18.5 tonne/yr at Barstow. Overall, this model presents a critical tool for streamlining the translation of experimental solar-driven electrochemical research to real-world implementation.

Yap, Kyra M. K.↗
DOE OSTI2024

Advancing Insights into Electrochemical Pre‐Treatments of Supported Nanoparticle Electrocatalysts by Combining a Design of Experiments Strategy with In Situ Characterization

Activation, break-in, and/or pre-treatment protocols are generally applied to energy conversion devices before regular operation to reach stable performance. There remains much to understand about the relationships among physical properties, performance, and electrochemical pre-treatments. Here, a design-of-experiments (DoE) strategy is employed to address this gap by demonstrating the influence of five pre-treatment parameters for carbon-supported Pt-nanoparticle catalysts on the electrocatalytic oxygen reduction reaction (ORR). A subset of pre-treatments, developed using a central composite design, are tested in a flow cell combined with an inductively-coupled plasma mass spectrometer (on-line ICP-MS). The DoE-based approach facilitates comprehensive insights from two orders of magnitude fewer experiments than a conventional grid search. The coupled on-line ICP-MS setup enables effective catalysis and real-time catalyst dissolution data. Leveraging insights from DoE for on-line ICP-MS and additional characterization, a model is built between the degradation of a multi-dimensional supported Pt surface, its performance, and applied electrochemical parameters. These investigations identify surface modifications, such as oxidation, and subsequent restructuring of Pt during pre-treatment as a primary cause of performance deterioration during ORR. By combining DoE with advanced characterization techniques, a powerful approach is demonstrated to gain a mechanistic understanding of pre-treatment protocols that can be broadly adapted to various reaction chemistries.

Platinum↗
DOE OSTI2024

Alkali cation-induced cathodic corrosion in Cu electrocatalysts

The reconstruction of Cu catalysts during electrochemical reduction of CO 2 is a widely known but poorly understood phenomenon. Herein, we examine the structural evolution of Cu nanocubes under CO 2 reduction reaction and its relevant reaction conditions using identical location transmission electron microscopy, cyclic voltammetry, in situ X-ray absorption fine structure spectroscopy and ab initio molecular dynamics simulation. Our results suggest that Cu catalysts reconstruct via a hitherto unexplored yet critical pathway - alkali cation-induced cathodic corrosion, when the electrode potential is more negative than an onset value (e.g., –0.4 V RHE when using 0.1 M KHCO 3 ). Having alkali cations in the electrolyte is critical for such a process. Consequently, Cu catalysts will inevitably undergo surface reconstructions during a typical process of CO 2 reduction reaction, resulting in dynamic catalyst morphologies. While having these reconstructions does not necessarily preclude stable electrocatalytic reactions, they will indeed prohibit long-term selectivity and activity enhancement by controlling the morphology of Cu pre-catalysts. Alternatively, by operating Cu catalysts at less negative potentials in the CO electrochemical reduction, we show that Cu nanocubes can provide a much more stable selectivity advantage over spherical Cu nanoparticles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Sub-volt conversion of activated biochar and water for H 2 production near equilibrium via biochar-assisted water electrolysis

Sluggish water oxidation reactions limit water electrolysis for H 2 production, which can be alleviated by the use of carbon-based ma- terials like agricultural wastes as reducing agents. Biochar from such biomass can reduce equilibrium cell potentials at standard condi- tions from 1.23 V to 0.21 V by avoiding direct water splitting at the anode. However, some challenges hinder biochar oxidation, including poor biochar binding, electrode caking, and surface passivation. We find that enhanced C/O ratio, crystallinity, and negative zeta potential improve biochar oxidation kinetics at mod- erate temperatures. Smaller particle sizes and better mixing pre- vent electrode caking, enhancing biochar stability. Here, we report sub-volt biochar-coupled H 2 production, often referred to as a bio- char-assisted water electrolysis (BAWE), yielding 250 mA/g cat H 2 current at 100% Faradaic efficiency. Over 1 mA current was observed at a near-equilibrium cell potential of 0.2 V cell potential. Using a single-junction solar cell-powered BAWE, 15 mA H 2 is generated at 1 Sun, resulting in 4.8% solar-to-hydrogen efficiency, equivalent to 35% when the energy of H 2 relative to H 2 O (without biochar) is assumed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Tuning Two-Dimensional Phthalocyanine Dual Site Metal–Organic Framework Catalysts for the Oxygen Reduction Reaction

Metal-organic frameworks (MOFs) offer an interesting opportunity for catalysis, particularly for metal-nitrogen-carbon (M-N-C) motifs by providing an organized porous structural pattern and well-defined active sites for the oxygen reduction reaction (ORR), a key need for hydrogen fuel cells and related sustainable energy technologies. Here, in this work, we leverage electrochemical testing with computational models to study the electronic and structural properties in these systems and their relationship to ORR activity and stability based on dual transitional metal centers. These consists of two M1 metals with amine nodes coordinated to a single M2 metal with a phthalocyanine linker, where M1/M2 = Co, Ni, or Cu. Co-based metal centers, in particular Ni-Co, demonstrate the highest overall activity of all nine tested MOFs. Computationally, we identify the dominance of Co-sites, relative higher importance of the M2 site, and the role of layer M1 interactions on the ORR activity. Selectivity measurements indicate that M1 sites of MOFs, particularly Co, exhibits lowest (< 4%), and Ni demonstrates highest (>46%) two-electron selectivity, in good agreement with computational studies. Direct in-situ stability characterization, measuring dissolved metal ions, and calculations, using an alkaline stability metric, confirm that Co is the most stable metal in the MOF, while Cu exhibits notable instability at the M1. Overall, this study reveals how atomistic coupling of electronic and structural properties affects the ORR performance of dual site MOF catalysts and opens new avenues for tunable design and future development of these systems for practical electrochemical applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Operando investigations of the solid electrolyte interphase in the lithium mediated nitrogen reduction reaction

The lithium-mediated nitrogen reduction reaction (Li-NRR) represents a promising approach for electrochemical nitrogen activation, in which the solid electrolyte interphase (SEI) layer formed on the electrochemically plated lithium plays a key role. Herein, we used time-resolved, operando, grazing incidence wide-angle X-ray scattering (GI WAXS) to identify SEI species and reaction intermediates in the Li-NRR, comparing LiBF 4 and LiClO 4 as electrolyte salts. In this study, we demonstrated how the SEI composition influences the Li-NRR performance by regulating proton transport to the plated Li. When LiBF 4 is used as the electrolyte salt, the formation of LiF and lithium ethoxide (LiEtO) is observed. Reaction intermediates such as LiH and LiN x H y species were found and provide insight into reaction pathways towards undesired and desired products, respectively. Observed restructuring of the Cu (111) single crystal substrate also indicates interaction with plated Li that could possibly influence the Li-NRR performance. Together, these experiments give molecular insight into how to design Li-NRR systems and their SEI layers for optimal performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Interpretable Machine Learning Models for Practical Antimonate Electrocatalyst Performance

Computationally predicting the performance of catalysts under reaction conditions is a challenging task due to the complexity of catalytic surfaces and their evolution in situ, different reaction paths, and the presence of solid-liquid interfaces in the case of electrochemistry. We demonstrate here how relatively simple machine learning models can be found that enable prediction of experimentally observed onset potentials. Inputs to our model are comprised of data from the oxygen reduction reaction on non-precious transition-metal antimony oxide nanoparticulate catalysts with a combination of experimental conditions and computationally affordable bulk atomic and electronic structural descriptors from density functional theory simulations. From human-interpretable genetic programming models, we identify key experimental descriptors and key supplemental bulk electronic and atomic structural descriptors that govern trends in onset potentials for these oxides and deduce how these descriptors should be tuned to increase onset potentials. Here, we finally validate these machine learning predictions by experimentally confirming that scandium as a dopant in nickel antimony oxide leads to a desired onset potential increase. Macroscopic experimental factors are found to be crucially important descriptors to be considered for models of catalytic performance, highlighting the important role machine learning can play here even in the presence of small datasets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Modeling diurnal and annual ethylene generation from solar-driven electrochemical CO 2 reduction devices

Integrated solar fuels devices for CO 2 reduction (CO 2 R) are a promising technology class towards reducing carbon emissions. Designing integrated CO 2 R solar fuels devices requires careful co-design of electrochemical and photovoltaic components as well as consideration of the diurnal and seasonal effects of solar irradiance, temperature, and other meteorological factors expected for ‘on-sun’ deployment. Using a photovoltaic-electrochemical (PV-EC) platform, we developed a temperature and potential-dependent diurnal and annual model using experimentally-determined CO 2 R performance of Cu-based electrocatalysts, local meteorological data from the National Solar Radiation Database (NSRD), and modeled performance of commercial c-Si PVs. Here we simulated gaseous diurnal product outputs with and without the effects of ambient temperature. From these outputs, we observed seasonal variation in gaseous product generation, with up to two-fold increases in ethylene productivity between the Winter and Summer, analyzed the consequences of dynamic cloud coverage, and identified periods where device cooling/heating mechanisms could be implemented to maximize ethylene generation. Finally, we modeled the annual ethylene generation for a scaled 1 MW solar farm at three different locations (Beijing, CN; Sydney, AUS; Barstow, CA) to determine the consequences of local meteorological climates on PV-EC CO 2 R product output, recording a maximum ethylene output of 18.5 tonne per year at Barstow. Overall, this model presents a critical tool for streamlining the translation of experimental solar-driven electrochemical research to real-world implementation.

14 SOLAR ENERGY↗
DOE OSTI2024

Modeling Planar Electrodes and Zero–Gap Membrane Electrode Assemblies for CO 2 Electrolysis

Multiphysics modeling enables probing of conditions inside a CO 2 electrolyzer that are difficult to measure, such as local concentrations and pH, as well as rapid testing of possible design changes. A one-dimensional model for a zero-gap membrane electrode assembly (MEA) CO 2 electrolyzer was developed with the assumption that catalyst layers interact with the membrane ionomer such that the ionomer affects the underlying kinetics. The kinetics for bicarbonate reacting to form hydrogen are fit using a planar electrode model for silver with an ionomer coating. The MEA model results are validated against experimental studies for current density and product selectivity. Flooding of the cathode is modeled using saturation curves, and results show that blocked pores in the microporous layer play a significant role in limiting the mass transport at high potentials (>2.8 V). Sensitivity studies showed that CO Faradaic efficiency can be increased by decreasing catalyst layer thickness and porosity, and decreasing KHCO 3 concentration.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Multi-scale physics of bipolar membranes in electrochemical processes

Bipolar membranes (BPMs) enable control of ion concentrations and fluxes in electrochemical cells suitable for a wide range of applications. Here, in this work, we present the multi-scale physics of BPMs in an electrochemical engineering context and articulate design principles to drive the development of advanced BPMs. The chemistry, structure, and physics of BPMs are illustrated and related to the thermodynamics, transport phenomena, and chemical kinetics that dictate ion and species fluxes and selectivity. These interactions give rise to emergent structure–property–performance relationships that yield design criteria for BPMs that achieve high permselectivity, durability, and voltaic efficiency. The resulting performance trade-offs for BPMs are presented in the context of emerging applications in energy conversion or storage, and environmental remediation. By connecting the fundamental physical phenomena in BPMs to device-level performance and engineering, we aim to facilitate the development of next-generation BPMs for sustainable electrochemical processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Controlling Mass Transport in Direct Carbon Dioxide Zero-Gap Electrolyzers via Cell Compression

The development of high-performance CO 2 electrolyzers is crucial for accelerating the sustainable production of fuels and chemicals integrated with renewable energy sources. Here, we introduce a methodology to actively control mass transport inside a realistic zero-gap membrane electrode assembly of a CO 2 electrolyzer by varying the gasket thickness, which consequently changes the cell compression. This allows control over the thickness and porosity of the gas diffusion electrodes, influencing the overall electrolyzer performance, as demonstrated using Ag-deposited electrodes. At low operating voltages (<2.9 V), both high- and low-compression electrolyzers exhibit similar faradaic efficiencies and partial current densities for CO formation. However, at high voltages, the low-compression electrolyzer with high electrode porosity demonstrates superior CO selectivity and activity with suppressed H 2 formation. These experimental results are validated by the computational membrane electrode assembly (MEA) model developed by using the measured in situ electrode thicknesses and electrode porosities. Additionally, liquid electrolyte saturation at the catalyst layer is found to play a dominant role in determining the mass transport, resulting in a decreased electrolyzer performance with low electrode porosity. Finally, the systematic investigation in this study improves the understanding of the transport dynamics in MEA-based devices and provides insights into optimizing device design parameters for industry-relevant CO 2 electrolysis.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

High-performance ionomerless cathode anion-exchange membrane fuel cells with ultra-low-loading Ag–Pd alloy electrocatalysts

Rapid translation of catalysts from fundamental studies to high-performance devices could facilitate the process of developing and commercializing anion-exchange membrane fuel cells (AEMFCs). Traditionally, translation from material screening in three-electrode rotating disk electrode (RDE) cells to AEMFCs is complicated by differences in microenvironments, e.g. solid ionomer/membrane vs liquid electrolyte. Herein, we introduce a platform for translation to devices that utilizes ionomerless ultra-low-loading Ag-Pd alloy electrocatalyst cathodes synthesized by co-physical vapor deposition (PVD). Our ionomerless cathodes allow for systematic H 2 -O 2 AEMFC experiments while demonstrating comparable activity trends to those in three-electrode cells. Furthermore, here we show that our Ag 10 Pd 90 -based AEMFC reaches a peak power density of ~1 W cm$_{geo}^{-2}$ and ~10 W mg$_{PGM Cathode}^{-1}$ satisfying the U.S. Department of Energy’s platinum-group-metal (PGM) loading and cost targets. Our approach shows promise in facilitating the rapid translation between three-electrode studies and AEMFCs, offering a simple and effective design for decreasing PGM loadings.

25 ENERGY STORAGE↗