Elucidating the Role of the Electric Field at the Ni/YSZ Electrode: A DFT Study

To decrease the deactivation of the Ni/YSZ electrode during hydrocarbon oxidation in solid oxide fuel cells (SOFCs) and coelectrolysis of H₂O and CO₂ in a solid oxide electrolysis cell (SOEC), it is very important to first understand oxygen vacancy formation at the triple-phase boundary (TPB) of Ni/YSZ because such vacancies are the active sites for coke formation and sulfur poisoning. Furthermore, the effect of the electric fields on oxygen vacancy formation must be investigated because such fields could potentially be used to alter the Ni/YSZ system and directly modify its electrocatalytic performance. In this study, three scenarios were considered: (i) oxygen vacancy formation in YSZ with and without a Ni cluster, (ii) oxygen vacancy formation and oxygen diffusion in YSZ and Ni/YSZ at different oxygen vacancy concentrations, and (iii) the effect of the electric fields on scenarios (i) and (ii). Our computational results show that the oxygen-enriched Ni/YSZ (Ni/YSZ+O) electrode is most likely to occur in an oxygen-enriched environment, even in the presence of different electric fields. Both large negative and positive electric fields could lead to more active TPB vacancies by reducing the vacancy formation energies of the Ni/YSZ+O electrode to a certain degree. Both charge distribution and effective dipole moments verify the qualitative findings concerning field influences on oxygen vacancy formation in Ni/YSZ. Overall, this investigation provides guidance for designing a Ni/YSZ electrode with an improved electrocatalytic performance via the simulated electric fields

Hydrogen Oxidation and Water Dissociation over an Oxygen-Enriched Ni/YSZ Electrode in the Presence of an Electric Field: A First-Principles-Based Microkinetic Model

Elucidating the sulfur poisoning or coking for electrochemical cells (e.g., a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC)) is highly dependent on studying such mechanisms by which said catalysts deactivate under experimentally relevant conditions. For a SOFC (or a SOEC) system, this requires the inclusion of the effect of a negative (or a positive) electric field when modeling the elementary catalytic reactions. In this contribution, the field effects on hydrogen oxidation and water decomposition over the triple phase boundary (TPB) region of the Ni/YSZ electrode are investigated using a field-dependent microkinetic model. Our results first show that the field effects on the Ni surface of the Ni/(YSZ+O) model are different as compared to a pure Ni(111) surface due to a difference in the charge distribution on the said surfaces. Between 400 to 1200 K, the negative fields assist in hydrogen oxidation over the TPB region of the Ni/(YSZ+O) cermet, which can potentially result in a larger probability for the said model to have oxygen vacancies at the TPB. Consequently, deactivation from sulfur poisoning or coking can increase since such vacancies are active for sulfur adsorption or coke formation. On the other hand, a high positive electric field can decrease the water decomposition rate to form hydrogen as compared to when the field is absent. Overall, this study provides insights for considering the electric field effects on the hydrogen oxidation and water dissociation over Ni/(YSZ+O) electrodes

CO₂RR-to-CO Enhanced by Self-Assembled Monolayer and Ag Catalytic Interface

Electroreduction of CO2 to fuels (e.g., CO) catalyzed by transition metal catalysts is a promising approach to mitigate global warming issues, but it has limitations of low catalytic activity and high applied potential. The interface between self-assembled monolayers (SAMs) and transition metal surfaces could potentially stabilize the active surfaces and create bifunctional catalytic sites to improve the catalytic performance. Herein, we proposed a new type of electrocatalyst, 4-mercaptobenzonitrile (4-MBN) SAMs-modulated Ag, as an example to enhance the reaction of CO2-to-CO over Ag. We first examined the stabilization effect of 4-MBN SAMs over Ag and then evaluated the CO2-to-CO over 4-MBN/Ag (i.e., Ag(111), Ag(100), and Ag(211)) using density functional theory calculations. Our results showed that 4-MBN SAMs strongly bonded over Ag(211), and hence stabilized the Ag step site, the potential active site for the CO2-to-CO reaction. Notably, 4-MBN SAMs introduced new organic active sites. The new organic active sites mitigated the formation free energy of the key intermediate *OCOH (the potential rate-limiting step of CO2-to-CO) via a strong C–N bond up to 0.65 eV, compared to that of the pristine Ag surface. Consequently, CO2-to-CO can possibly occur at a lower applied potential at the SAM/Ag interface than that over the pristine Ag surface. Overall, our theoretical work demonstrates that a SAMs/metal interface stabilizes step sites, creates dual organic–inorganic active sites, modifies surface electronic properties, and provides a new strategy for the electrocatalyst design with potentially enhanced energy efficiency

Improving Ni Catalysts Using Electric Fields: A DFT and Experimental Study of the Methane Steam Reforming Reaction

This work demonstrates the benefits of applying an external electric field to the methane steam reforming reaction (MSR) in order to tune the catalytic activity of Ni. Through combined DFT calculations and experimental work, we present evidence for the usefulness of an electric field in improving the efficiency of current MSR processesnamely by reducing coke formation and lowering the overall temperature requirements. We focus on the influence of an electric field on (i) the MSR mechanisms, (ii) the rate-limiting step of the most favorable MSR mechanism, (iii) the methanol synthesis reaction during the MSR reaction, and (iv) the formation of coke. Our computational results show that an electric field can change the most favorable MSR mechanism as well as alter the values of the rate constants and equilibrium constants at certain temperatures and, hence, significantly affect the kinetic properties of the overall MSR reaction. Both computational and experimental results also suggest that a positive electric field can impede the formation of coke over a Ni catalytic surface during the MSR reaction. Moreover, the presence of a negative electric field notably increases the rate constant and the equilibrium constant for the methanol synthesis reaction, which suggests a possible direct route from methane to methanol. Finally, a field-induced Brønsted–Evans–Polanyi (BEP) relationship was developed for C−H bond cleavage, C−O bond cleavage, and O−H bond formation over a Ni catalytic surface. Overall, this investigation strengthens our understanding of the effect of an electric field on the Ni-based MSR catalytic system and highlights the benefits of designing heterogeneous reactions under applied electric fields

Deep Learning-Assisted Investigation of Electric Field–Dipole Effects on Catalytic Ammonia Synthesis

External electric fields can modify binding energies of reactive surface species and enhance catalytic performance of heterogeneously catalyzed reactions. In this work, we used density functional theory (DFT) calculationsassisted and accelerated by a deep learning algorithmto investigate the extent to which ruthenium-catalyzed ammonia synthesis would benefit from application of such external electric fields. This strategy allows us to determine which electronic properties control a molecule’s degree of interaction with external electric fields. Our results show that (1) field-dependent adsorption/reaction energies are closely correlated to the dipole moments of intermediates over the surface, (2) a positive field promotes ammonia synthesis by lowering the overall energetics and decreasing the activation barriers of the potential rate-limiting steps (e.g., NH2 hydrogenation) over Ru, (3) a positive field (>0.6 V/Å) favors the reaction mechanism by avoiding kinetically unfavorable NN bond dissociation over Ru(1013), and (4) local adsorption environments (i.e., dipole moments of the intermediates in the gas phase, surface defects, and surface coverage of intermediates) influence the resulting surface adsorbates’ dipole moments and further modify field-dependent reaction energetics. The deep learning algorithm developed here accelerates field-dependent energy predictions with acceptable accuracies by five orders of magnitudes compared to DFT alone and has the capacity of transferability, which can predict field-dependent energetics of other catalytic surfaces with high-quality performance using little training data

Ambient Carbon-Neutral Ammonia Generation via a Cyclic Microwave Plasma Process

A novel reactor methodology was developed for chemical looping ammonia synthesis processes using microwave plasma for pre-activation of the stable dinitrogen molecule before reaching the catalyst surface. Microwave plasma-enhanced reactions benefit from higher production of activated species, modularity, quick startup, and lower voltage input than competing plasma-catalysis technologies. Simple, economical, and environmentally benign metallic iron catalysts were used in a cyclical atmospheric pressure synthesis of ammonia. Rates of up to 420.9 μmol min–1 g–1 were observed under mild nitriding conditions. Reaction studies showed that both surface-mediated and bulk-mediated reaction domains were found to exist depending on the time under plasma treatment. The associated density functional theory (DFT) calculations indicated that a higher temperature promoted more nitrogen species in the bulk of iron catalysts but the equilibrium limited the nitrogen converion to ammonia, and vice versa. Generation of vibrationally active N2 and, N2+ ions is associated with lower bulk nitridation temperatures and increased nitrogen contents versus thermal-only systems. Additionally, the kinetics of other transition metal chemical looping ammonia synthesis catalysts (Mn and CoMo) were evaluated by high-resolution time-on-stream kinetic analysis and optical plasma characterization. This study sheds new light on phenomena arising in transient nitrogen storage, kinetics, effect of plasma treatment, apparent activation energies, and rate-limiting reaction steps

Enhanced CO₂ Reactive Capture and Conversion Using Aminothiolate Ligand–Metal Interface

Metallic catalyst modification by organic ligands is an emerging catalyst design in enhancing the activity and selectivity of electrocatalytic carbon dioxide (CO2) reactive capture and reduction to value-added fuels. However, a lack of fundamental science on how these ligand–metal interfaces interact with CO2 and key intermediates under working conditions has resulted in a trial-and-error approach for experimental designs. With the aid of density functional theory calculations, we provided a comprehensive mechanism study of CO2 reduction to multicarbon products over aminothiolate-coated copper (Cu) catalysts. Our results indicate that the CO2 reduction performance was closely related to the alkyl chain length, ligand coverage, ligand configuration, and Cu facet. The aminothiolate ligand–Cu interface significantly promoted initial CO2 activation and lowered the activation barrier of carbon–carbon coupling through the organic (nitrogen (N)) and inorganic (Cu) interfacial active sites. Experimentally, the selectivity and partial current density of the multicarbon products over aminothiolate-coated Cu increased by 1.5-fold and 2-fold, respectively, as compared to the pristine Cu at −1.16 VRHE, consistent with our theoretical findings. This work highlights the promising strategy of designing the ligand–metal interface for CO2 reactive capture and conversion to multicarbon products

Electrochemical C–N Bond Formation within Boron Imidazolate Cages Featuring Single Copper Sites

Electrocatalysis expands the ability to generate industrially relevant chemicals locally and on-demand with intermittent renewable energy, thereby improving grid resiliency and reducing supply logistics. Herein, we report the feasibility of using molecular copper boron-imidazolate cages, BIF-29­(Cu), to enable coupling between the electroreduction reaction of CO2 (CO2RR) with NO3– reduction (NO3RR) to produce urea with high selectivity of 68.5% and activity of 424 μA cm–2. Remarkably, BIF-29­(Cu) is among the most selective systems for this multistep C–N coupling to-date, despite possessing isolated single-metal sites. The mechanism for C–N bond formation was probed with a combination of electrochemical analysis, in situ spectroscopy, and atomic-scale simulations. We found that NO3RR and CO2RR occur in tandem at separate copper sites with the most favorable C–N coupling pathway following the condensation between *CO and NH2OH to produce urea. This work highlights the utility of supramolecular metal–organic cages with atomically discrete active sites to enable highly efficient coupling reactions

Table1_The viability of implementing hydrogen in the Commonwealth of Massachusetts.docx

In recent years, there has been an increased interest in hydrogen energy due to a desire to reduce greenhouse gas emissions by utilizing hydrogen for numerous applications. Some countries (e.g., Japan, Iceland, and parts of Europe) have made great strides in the advancement of hydrogen generation and utilization. However, in the United States, there remains significant reservation and public uncertainty on the use and integration of hydrogen into the energy ecosystem. Massachusetts, similar to many other states and small countries, faces technical, infrastructure, policy, safety, and acceptance challenges with regards to hydrogen production and utilization. A hydrogen economy has the potential to provide economic benefits, a reduction in greenhouse gas emissions, and sector coupling to provide a resilient energy grid. In this paper, the issues associated with integrating hydrogen into Massachusetts and other similar states or regions are studied to determine which hydrogen applications have the most potential, understand the technical and integration challenges, and identify how a hydrogen energy economy may be beneficial. Additionally, hydrogen’s safety concerns and possible contribution to greenhouse gas emissions are also reviewed. Ultimately, a set of eight recommendations is made to guide the Commonwealth’s consideration of hydrogen as a key component of its policies on carbon emissions and energy.</p