bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Surface Photovoltage Provides Quasi Fermi Level Splitting and Minority Carrier Electrochemical Potential of BiVO4 /Liquid Junctions Under Illumination
Authors: Daemi Sahar , Khan Sherdil , Xiao Chengcan , Mendoza Hervin Errol , Osterloh Frank E
Published: November 2022

The solar energy conversion efficiency of semiconductor-liquid junctions is determined by their photovoltage and by their photocurrent under illumination. Photoelectrochemistry (PEC) gives information on the current, but not on the photovoltage or the quasi Fermi level splitting (qFLS), which for slow redox couples is obscured by kinetic overpotentials and surface states. Here we show that surface photovoltage spectroscopy (SPS) provides direct measurement of the qFLS potential in BiVO4-electrolyte contacts. Measurements were done with a vibrating Kelvin probe on FTO deposited BiVO4 films in contact with aqueous electrolytes containing triiodide/iodide, oxygen/ hydrogen peroxide, or sulfate/sulfite redox couples and for iron-oxyhydroxide modified BiVO4 films. The triiodide/iodide couple, for example, yields qFLS=0.78 V under 49 mW/cm-2 (400 nm LED) illumination, comparable to the photovoltage from PEC (0.79 V). Furthermore, the reversibility of the redox reactions determines the reversibility of the SPS transients. For example, the triiodide/iodide couple gives nearly complete SPS reversibility on the 20 sec timescale, while the sulfate/sulfite couple gives an irreversible photovoltage signal. Lastly, by combining the SPS data with the majority carrier potential from open circuit potential measurements, the minority carrier electrochemical potentials, Efp can be obtained for all systems. For instance, Efp = 1.0 V vs RHE for the BiVO4 - triiodide/iodide junction and Efp = 0.26 V vs RHE for the sulfate/sulfite junction. These shows that BiVO4 can photoelectrochemically oxidize both redox couples, without applied bias. These results shed new light on the photoelectrochemistry of BiVO4, an important photoanode material for solar hydrogen production from water.

Figure 1
(Invited) In Situ Time-Resolved Vibrational Spectroscopic Probe of Catalyst Structures, Dynamics and Reaction Mechanisms on Semiconductor Photoelectrodes
Authors: Lian Tianquan
Published: November 2022

Attachment of molecular catalysts onto semiconductor or metal electrodes is a promising approach for rational design of efficient photoelectrochemical cells for solar water splitting and CO2 reduction. The understanding and improvement of such devices requires fundamental understanding of the structure and dynamics of catalysts as well as the interfacial electrolyte environment at electrode-liquid interfaces. Vibrational sum frequency generation (VSFG) spectroscopy is an in situ interface specific technique for probing interfacial properties at the semiconductor electrode/electrolyte interface at the molecular level. In this talk, we discuss our recent efforts in developing and applying in situ time-resolved VSFG for studying structural and dynamics of rhenium bipyridyl and other molecular CO2 reduction catalysts on semiconductor and metal electrodes. We have shown that by combining VSFG experiment with advanced computational modeling, catalyst adsorption geometry can be determined; through electrochemical Stark effect, local electric field and the potential profile in the electric double layer under light and dark conditions can be directly measured; using VSFG as a time-dependent probe, the interfacial charge transfer dynamics can be directly measured and key reactive intermediates can be identified.
(Invited) A Novel Pathway for the Construction of Core–Shell Photocathodes for PEC Applications
Authors: Solarska Renata
Published: November 2022

Semiconductor hetero-nanostructures are of great interest for practical use. In this presentation, a novel approach to production of CuO|CuFe2O4 core-shell structure by thermal conversion of CuFe Prussian Blue Analogues will be demonstrated. It represents a new family of photocatalysts that can be used as photoelectrodes able to produce hydrogen under broad spectrum of the visible light. The outstanding photoelectrochemical properties of the photocathodes of CuO|CuFe2O4 have been studied with use of combinatory photo-electrochemical instrumental techniques which proved the electrodes were stable over the whole water photolysis run under relatively positive potentials. Their outstanding performance have been explained by coupling of two charge transfer mechanisms occurring in core-shell architectures. Then, the CuO:Zn nanostructures, in which the photoelectrochemical properties were governed by Fermi level pinning of Zn ions would be presented as well. The implementation of Zn ions enlarged the space charge region and triggered electron availability for the photolysis of water which is unusual for p-type semiconductors. Furthermore, the excellent crystallinity, high surface area, and adhesion to the FTO remarkably improved the photocatalytic activity of the CuO:Zn thin film with cathodic photocurrent of 4 mAcm-2 and a quantum efficiency of 35%, making it promising for hydrogen production.
Steady State Performance Evaluation of Noble-Metal Free Bifunctional Electrode for Overall Water Splitting
Authors: Kumaran Yamini , Gherasoiu Iulian , Efstathiadis Harry
Published: November 2022

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst that is cost effective and can show a comparable HER (Hydrogen Evolution Reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen Evolution Reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance. In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering. This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear Sweep Voltammetry)/CV (Cyclic Voltammetry). This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.
Using Synchrotron Based x-Ray Analysis to Understand the Influence of Cations on CO2 Electrolysis Performance
Authors: Garg Sahil , Xu Qiucheng , Moss Asger Barkholt , Mirolo Marta , Drnec Jakub , Seger Brian
Published: November 2022

Given that society will always need carbon based products such as plastics, nylons and organic solvents and probably high density fuels for aviation and shipping, this entails there is an urgent need to produce carbon based products sustainably. CO2 electrolysis to building-block chemicals such as CO, ethanol, and ethylene shows great promise, however there is still substantial development and understanding needed to operate at industrially relevant current densities (>100 mA/cm2) and maintaining stable performance for 1000s of hours.

This talk will focus on using in synchrotron based x-rays to analyze a zero-gap membrane electrode CO2 electrolysis device in operando. Not only does x-ray diffraction allow us to see changing oxidation state of our copper catalyst, but we can also see the Bragg peaks of any formation of salt precipitations in-situ, which is a substantial issue in these devices since they block mass transfer. Furthermore by analyzing background scattering, we can also visualize electrolyte variations within our cathodic gas diffusion layer. By having our in-operando device attached to both an in-line gas chromatograph and mass spectrometer we can relate product variations to variation in parameters visualized via the x-ray analysis and thus have a more comprehensive understanding of our devices. In this talk, we will discuss how variations in both anode electrolyte concentration and type (e.g. Li, Cs) have a substantial impact in both electrolyte penetration into the cathodic gas diffusion layer as well as how and where these salts may precipitate out and cause mass transfer issues.
Direct in Situ Observation of Surface Charge Accumulation Under Water Oxidation Conditions By Electric Field Induced Second Harmonic Generation Measurements
Authors: Zhao Fengyi , Lian Tianquan , Xu Zihao , Suo Sa , Hill Craig L , Musaev Djamaladdin G
Published: November 2022

The water oxidation reaction is considered as the bottleneck and rate-determining step in photoelectrochemical water-splitting processes. To achieve efficient water oxidation on the photoanode, sufficient built-in potential on semiconductors under light illumination needs to be maintained. Herein, we introduced the in-situ Electric Field Induced Second Harmonic Generation (EFISH) technique to probe the change of built-in potential under the water oxidation reaction process of a single-crystal rutile TiO2 photoanode. Under the dark condition, parabolic relation between the second harmonic generation signal and applied potential is observed in TiO2 depletion region. Under UV illumination, the EFISH signal decreased compared to dark at the photocurrent saturation potential region. Change in the signal is attributed to the decrease of built-in potential in TiO2. The amount of built-in potential change increased with light illumination and saturated at 520 mV under 15mW/cm2 360 nm UV illumination in an unbuffered solution. This light-induced band edge unpinning effect can be explained by the accumulation of holes at surface states and surface protons at Helmholtz layer that are generated under illumination. Kinetic isotope EFISH experiments suggest that proton-coupled electron transfer (PCET) is the rate-determining step in water oxidation process. Screening of built-in potential under illumination can be mitigated by adding buffer ions, suggesting that the rate-determining step can be altered by changing the solution microenvironment.
Optimization of Z-Scheme Photocatalytic Reactors for Solar Water Splitting
Authors: Chen Zejie , Keene Sam , Gaieck William , Phun Gabriel S. , Stinson Robert , Stinson William D. H. , Wang Yinxian , Barrera Luisa , Chen Zijie , Mayer Mike , Watanabe Kenta , Kim Tea Yon , Zutter Brian , Lapp Aliya S. , Xu Mingjie , Acevedo Yaset , Huya-Kouadio Jennie , James Brian , Kudo Akihiko , Pan Xiaoqing , Hurst Katherine , Talin A. Alec , Esposito Daniel V. , Bala Chandran Rohini , Ardo Shane
Published: November 2022

The U.S. Department of Energy recently announced its first Energy Earthshot on Clean Hydrogen, with a cost target of $1/kg-H2 by 2031. Assuming future utility-scale grid electricity prices from photovoltaics ($0.02/kWh), 80% of the cost of H2 would come from performing low-temperature water electrolysis at its thermoneutral voltage, with zero additional overpotential. This fact motivates alternative, less-expensive means of using light to generate mobile charge carriers than photovoltaics, and reactor designs with exceedingly low capital costs, like those we recently invented. Systems using low capital cost reactors benefit from low-voltage operation, which represents a paradigm shift from current state-of-the-art electrolyzers that aim to operate at high current densities. Analytical models predict that solar photocatalytic water splitting inherently operates at low voltages through use of an ensemble of optically thin photoabsorbers each operating at a low rate. Collectively the ensemble exhibits larger overall solar-to-hydrogen conversion efficiencies in comparison to optically thick designs. In efforts to attain these predicted higher efficiencies, we are performing detailed studies on the properties of state-of-the-art doped SrTiO3 and BiVO4 photocatalyst particles. During my talk, I will share our recent efforts in atomic-layer deposited ultrathin oxide coatings to impart redox selectivity and materials stability, single-photocatalyst-particle current–potential behavior and mobile charge carrier properties, and atomic-level information on dopant distributions and materials interfaces obtained from electron microscopies and X-ray spectroscopies. Collectively, our discoveries provide new design guidelines and additional research pathways for the development of effective composite materials to serve as active components in techno-economically viable artificial photosynthetic devices.
Large-Scale Synthesis of Photocatalytic TiO2 Nanotube Layers
Authors: Sopha Hanna , Baudys Michal , Krysa Josef , Macak Jan M.
Published: November 2022

Self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 15 years motivated for their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2]. The synthesis of the 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheets in various electrolytes.

By now, the synthesis of TiO2 nanotube layers with different nanotube dimensions (diameter, length) and the application of these nanotube layers is well established on the laboratory scale. However, for real applications outside the laboratory scale, such as photocatalysis [3], TiO2 nanotube layers of much larger size are necessary. To date, just a few efforts were carried out to scale up the size of the nanotube layers to more than a few cm2 [3-7] due to the difficulty of controlling the parameters of the anodization process on a larger scale. The main challenge is the huge current received during the anodization of large substrates. This, in turn, leads to an increase in the electrolyte temperature that may result in dielectric breakdown of the growing nanotube layers.

In this presentation, the preparation of TiO2 nanotube layers on larger area titanium substrates (dozens of cm2) will be discussed, taking into account the control of the anodization parameters. The TiO2 nanotube layers with different thicknesses and nanotube diameters were employed for gas phase photocatalysis, following the ISO standards [3,8]. Experimental details and photocatalytic results will be presented and discussed.

References

[1] J.M. Macak, H. Tsuchiya, A. Ghicov, K. Yasuda, R. Hahn, S. Bauer, P. Schmuki, Curr. Opin. Solid State Mater., 11 (2007) 3.

[2] K. Lee, A. Mazare, P. Schmuki, Chem. Rev., 114 (2014) 9385.

[3] H. Sopha, M. Baudys, M. Krbal, R. Zazpe, J. Prikryl, J. Krysa, J.M. Macak, Electrochem. Commun., 97 (2018) 91.

[4] S. Franz, D. Perego, O. Marchese, M. Bestetti, J. Water Chem. Tech., 37 (2015) 108.

[5] H.-I. Kim, D. Kim, W. Kim, Y.-C. Ha, S.-J. Sim, S. Kim, W. Choi, Appl. Catal. A: Gen., 521 (2016) 174.

[6] J.P. Ghosh, G. Achari, C.H. Langford, Water Environ. Res., 88 (2016) 785.

[7] C. Xiang, L. Sun, Y. Wang, G. Wang, X. Zhao, S. Zhang, J. Phys. Chem. C 121 (2017) 15448.

[8] H.Sopha, M. Baudys, J. Krýsa, J. M. Macak, Applied Mater. Today, submitted.
3D Core-Shell Heterostructures of WO3/Bi2MoO6 and MoS2/BiVO4 for Efficient Photoelectrochemical Water Splitting
Authors: Shim Jae-Jin , Mohamed Mostafa Saad Sayed , Al Mahmud Abdullah , Shagar Md. Mahmud Hasan.
Published: November 2022

Hydrogen has attracted increasing attention as clean energy for fuel cells over the past decade. Photoelectrochemical (PEC) water splitting is considered the most feasible production method. However, its practical efficiency depends significantly on the photogeneration rate of electron (e−) and hole (h+) on a semiconductor photoanode and the rapid separation of these charge carriers. Also, a proper match of small and large bandgap positions is necessary. 3D core-shell heterostructures of WO3/Bi2MoO6/Co‐Pi and BiVO4/MoS2 were synthesized using hydrothermal/electrodeposition and electrodeposition/plasma-enhanced atomic layer deposition (PECALD), respectively. The as-prepared WO3/Bi2MoO6/Co‐Pi hetero-photocatalyst exhibited significantly high photoelectrochemical activity, where its photocurrent efficiency was 4.6 times greater than that of the constituent WO3. For the BiVO4/MoS2 photoelectrode, an optimal thickness of the MoS2 layer was controlled by the number of PEALD cycles. The highest photocurrent (2.1 mA cm-2) was produced from the electrode with a 6 nm layer-thickness, 2.4 times higher than the pristine BiVO4 at an external bias of 1 V vs. Ag/AgCl. The appropriate bandgap alignment between layers can corroborate such drastic improvement in the PEC properties. A detailed investigation into the photoelectrochemical reaction mechanism showed that enhancement of the PEC performance was attributed to the finely deposited MoS2 layer, which expands the spectral absorption edge of solar light and enhances the suppression of electron-hole pair recombination because of the proper alignment match between the two semiconductors with a small and large bandgap. Furthermore, a heterojunction charge-transfer mechanism was proposed to verify the role of the co-catalyst, Co‐Pi, in enhancing the photocurrent at the WO3/Bi2MoO6 photoanode under the same applied bias.
(Invited) Steering Electrocatalytic CO2 Reduction Reactivity Using Microenvironments
Authors: Hahn Christopher
Published: November 2022

A key challenge in electrocatalysis is co-designing the catalyst and its microenvironment to work in concert to efficiently steer complex reaction networks. First, I will describe the development of a tandem catalysis strategy on Au/Cu electrocatalysts to control the potential energy landscape of the CO2 and CO reduction at length scales beyond the active site and achieve synergistic catalytic activity for alcohols superior to that of either Cu or Au. Next, I will provide examples of CO2 reduction on catalysts supported on gas diffusion electrodes to discuss how the intrinsic catalysis and mass transport are interconnected through microenvironments, leading to emergent catalytic properties under industrially relevant reaction rates. Finally, I will conclude by providing our perspective on key remaining challenges to the scale-up of CO2 electrolyzers within the context of electrifying the chemicals manufacturing sector.
Graphene Quantum Dots with Trace Copper Switching Product Selectivity during Electrochemical CO2/CO Reduction Reaction
Authors: Lyu Xiang
Published: November 2022

Electrochemical upgrading of carbon dioxide (CO2) into high-value chemicals and fuels provides a potential way to close the anthropogenic carbon cycle and store renewable energy. Heteroatoms (e.g., sulfur, nitrogen, boron, phosphorus, etc.) doped nanostructured carbon materials have been under development as a category of metal-free electrocatalysts for CO2/CO reduction due to their low cost, large specific surface area, and tunable electronic structure, and Cu is the only known metal catalyst that can convert CO2/CO to high-order hydrocarbons and oxygenates. However, little progress has been made in regulating Cu loading in heteroatoms doped nanostructured carbon materials for electrochemical CO2/CO reduction reaction (CO2/CORR). Herein, we report the effect of trace Cu loading in graphene quantum dots (GQDs) on CO2/CORR. Electrocatalytic measurements show a significant loading effect in both the activity and selectivity toward CO2/CORR. Increasing the Cu loading in GQDs will improve catalytic activity and selectivity toward C2 from C1 productions in CO2/CORR. The activity/selectivity relations provide a clean understanding of the synergistic effect of GQDs and trace Cu in CO2/CORR.
(Invited) Opportunities and Challenges for Biopolar Membrane-Based Electrosynthesis
Authors: Hatzell Marta
Published: November 2022

Over the last 3 decades, research on CO2 abatement technologies centered solely on carbon capture and storage (CCS). Here, technology focus is in the design of separations technologies to capture CO2 from concentrated point (e.g. flue gas) or dilute distributed sources (e.g. atmosphere) using amine absorption, adsorption, and membranes. Most of these technologies involve adsorbing or absorbing CO2 gas, releasing this gas, and then pressurizing it for storage. Thus, a number of different subsystems and specialized new equipment are needed resulting in high capital and operating costs. As a result, CO2 capture for CCS is economically unfavorable in the absence of utilization routes for the captured CO2. Electrolysis of CO2 is a viable potential pathway toward attaining utilization; however, carbon loss in traditional electrolysis architectures is a large limitation. To overcome this challenge, movement toward bipolar-membrane (BPM) based electrolysis cells have been proposed as a viable option. BPMs contain an anion and a cation exchange layer. At the interface of these membranes, a junction potential forms when a electric field is applied across the membrane. Thus, within a BPM electrolysis cell, charge balancing occurs through water electro dissociating at the interface of the anion and cation membrane, thereby forming charge carriers in the form of OH- and H+. The production of acid and base in situ allows for a continuous process with low carbon losses. The primary aim of this talk is to discuss the challenges and opportunities that exist with the development of proper catalyst and membranes for these systems for carbon capture and electrofuel production.
(Invited) The Electrosynthesis of Fuels from Direct Air Captured CO2
Authors: Sargent Edward Hartley
Published: November 2022

I will review advances in directly using capture liquids, such as carbonates and amines, as the source of CO2 in reactive capture based electrically-powered upgrade to fuels, focusing especially on methane, ethanol, and n-propanol.
(Invited) Electrochemical Valorization of Waste Activated Sludge to Chemicals
Authors: Botte Gerardine G.
Published: November 2022

Population growth have led to producing more solid waste from wastewater treatment plants (WWTPs), increasing both energy and cost for treatment and disposal of waste-activated sludge (WAS). If not treated properly, WAS poses serious threats to human health and the environment. The annual production of WAS reached 2 billion tons in 2011 worldwide and it is expected that this number will grow to 9.5 billion tons per year by 2050 [1]. Conversion of solid waste to value added chemicals and fuels could address environmental concerns imposed by the growing of WAS.

To confront these challenges, Botte’s research group is working in the electrochemical valorization of WAS to chemicals [2]. In this talk, we will describe recent findings in the electrocatalysis of sludge using transition metals for the synthesis of ammonia and short-chain fatty acids production. Short-chain fatty acids (e.g., acetic acid, propionic acid, butyric acid, etc.) are the intermediate chemicals in anaerobic digestion. The global market demand for short-chain fatty acids in 2020 was 18,500 kt and it is expected to increase annually by 3% per year over the next three years [3].

[1] Lemar, M.; De Fontaine, A., Energy Data Management Manual for the Wastewater Treatment Sector. Technical Report ORNL/SPR-2018/14 2017, United States. https://doi.org/10.2172/1432164

[2] Jafari, M.; Botte, G. G., Electrochemical treatment of sewage sludge and pathogen inactivation. Journal of Applied Electrochemistry
2021,
51 (1), 119-130.

[3] Ramos-Suarez, M.; Zhang, Y.; Outram, V., Current perspectives on acidogenic fermentation to produce volatile fatty acids from waste. Reviews in Environmental Science and Bio/Technology
2021,
20 (2), 439-478.
(Invited) Opportunities, Challenges, and Lessons Learnt from the Maturation of Emerging Water and CO2 Electrolysis Technologies
Authors: Corbett Paul , Verma Sumit
Published: November 2022

The deep decarbonization of difficult to abate sectors such as chemicals and aviation in the mid to long term will likely require the successful maturation, commercialization, and deployment of new CO2 capture as well as CO2 utilization technologies at the hundreds of millions of tonnes per annum scale or more. In this presentation, we will provide an overview of Shell’s recent R&D efforts in upscaling two key electrochemical technologies in this space from the bench to the pilot scale and beyond: water electrolysis and CO2/CO electrolysis. In particular, for the electrolysis of CO2/CO, we will present a systems view by comparing against alternative thermochemical options such as reverse water gas shift for syngas manufacturing and CO2 to methanol to olefins for ethylene production. The assessments will be made from a specific energy consumption, capital cost, critical materials availability, and ease of scalability point of view. Finally, we will present R&D gaps that could be collectively addressed by the broader community to further improve the technology’s future industrial prospects.
Water Management Gas Diffusion Layer Design Enables Improved Selectivity and Stability for CO2 Electrolysis
Authors: Zhang Tianyu , Pupucevski Max , Xu Hui
Published: November 2022

Electrochemical CO2 reduction to chemicals and fuels is a promising strategy to mitigate the ever-increasing carbon emission. The industrial application of CO2 electrolysis requires the electrolyzers to be operated at a high reaction rate, energy efficiency, and sufficient long-term stability. In the past, CO2 electrochemical reduction has focused on improving Faradaic efficiency and productivity in the past decades. For example, the Faradaic efficiency of CO2 to C2H4 conversion has reached 70% at a current density beyond 1 A cm-2. However, CO2 reduction long-term stability still faces multiple challenges. Flooding of gas diffusion layer (GDL) is among several crucial stability issues which block the CO2 transport pathway, thus resulting in low CO2 availability in the catalyst layer (CL). Specifically, regular GDLs suffer from low water breakthrough pressure, degrading hydrophobicity, and electro-osmosis. Some strategies have emerged to counter the flooding issue. For example, PTFE membranes with micropores were designed to replace regular carbon paper. The PTFE membrane is super-hydrophobic and chemically inert, which relieves the water breakthrough pressure and mitigates the hydrophobicity degradation. However, the PTFE membrane is non-conductive, thus imposing challenges for large-scale applications. In this work, we have designed a water management GDL, combining the advantages of regular carbon paper and PTFE membrane. This GDL comprises a PTFE microporous layer (MPL) for water management and a carbon fiber network for electron conduction. The PTFE MPL and carbon fiber network are compressed into one single layer. Using this design, the CO2 to C2H4 selectivity achieves over 50% at -0.66 V vs. RHE under current density beyond 300 mA cm-2. These results demonstrate the excellent gas transport efficiency and stability of the water management GDL, which can significantly facilitate the development of large-scale CO2 electrochemical conversion.

Acknowledgment: The project is financially supported by the Department of Energy’s Office of EERE under the Grant DE-EE000942l
(Digital Presentation) Highly Efficient and Selective CO2 Electroreduction to CO on Novel Metal-Nitrogen-Carbon (M-N-C) Catalyst
Authors: Delafontaine Laurent , Cosenza Alessio , Murphy Eamonn , Guo Shengyuan , Liu Yuanchao , Chen Jiazhe "Loki" , Atanassov Plamen
Published: November 2022

The electrocatalytic reduction of CO2 (CO2RR) to CO is an important component of emerging Carbon Capture and Utilization (CCU) technologies. This process often relies on expensive and rare metals such as silver and gold-based materials for high selectivity and conversion rate to CO1,2. It is desired to move away from these metals towards earth-abundant solid materials (e.g., carbon-based) which may serve as heterogeneous electrocatalysts for CO2RR. Herein, a series of novel carbon-based materials with exceptional selectivity/activity for the targeted production of CO is presented. This new class of hybrid catalyst materials have high CO2RR activity which is comparable to the state of the art atomically dispersed Metal-N-C synthesized by the sacrificial support method (SSM). The advantage of this new class of catalysts is that the use of harsh solvents such as nitric acid and potassium hydroxide which are usually required to remove the silica precursor is completely avoided. Not only does this make the immediate process more environmentally friendly, but it also significantly shortens the catalyst synthesis time which increases its industrial viability. The structure and activity of a series of catalysts with different metallic dopants (Fe, Co, Ni, Mn) are investigated. Using this new synthesis technique, a faradaic efficiency for CO formation (FEco) of 96.5 % at -0.3 V vs. RHE is achieved. FEco remains greater than 75 % over the potential range studied from -0.3 V to -1.1 V vs. RHE. By comparison, Fe-N-C by SSM method reaches a maximum FEco of 94.4 % at -0.7 V vs. RHE and FEco remains greater than 85 % over the same potential range.

References

1. Varela, A. S., Ranjbar Sahraie, N., Steinberg, J., Ju, W., Oh, H.-S., & Strasser, P. (2015). Metal-Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2 Electroreduction to CO and Hydrocarbons. In Angewandte Chemie International Edition.

2. Nguyen, D. L. T., Kim, Y., Hwang, Y. J., & Won, D. H. (2019). Progress in development of electrocatalyst for CO 2 conversion to selective CO production. In Carbon Energy.

Figure 1
Approaches on Improving Electroreduction of Carbon Monoxide to Acetate in Flow Electrolyzer
Authors: Guo Shengyuan , Liu Yuanchao , Murphy Eamonn , Delafontaine Laurent , Atanassov Plamen
Published: November 2022

Acetic acid (CH3COOH) is an important industrial chemical that is widely used in the generation of various products including medicals, food, solvent, synthetic fibers and fabrics. Although most acetic acid production today relies on the carbonylation process of methanol1, electrochemical synthesis method is a promising direction owing to its uniqueness in ambient conditions, utilization of renewable energy, and compatibility with bioengineering2. Cupper has the capability to electrochemically reduce CO2 to various C2 products but with low selectivity. The critical steps for acetate molecule generation from CO2/CO are the CO-dimerization and the nucleophilic attack of hydroxide ion on a ketene intermediate3, in which acetate production could be enhanced by electroreducing CO in alkaline electrolyte as compared to CO2 electroreduction in pH neutral solution. Meanwhile, the use of flow electrolyzer further improved the gas transport process by employing gas diffusion electrode, boosting the current and yield rate of products to industrial level. However, electrochemical reduction of CO to acetate on Cu-based electrocatalysts still suffers from low faradaic efficiency (<50%).4

In this talk, we will present our recent work on CO electroreduction to acetate by commercial Cu catalyst in flow electrolyzer. Parameters in terms of electrolyte molarity, catalyst loading, catalyst deposition method, and ionomer were manipulated to maximize the acetate production. Acetate was favored in high pH electrolyte by facilitating the nucleophilic attack of hydroxide ion process and suppressing competing proton transfer process towards ethylene and ethanol. Catalyst loading on gas diffusion electrode had great influence on the products selectivity, where low catalyst loading leans to ethylene generation, intermediate catalyst loading is selective to produce acetate, and high catalyst loading improves alcohol yield. A record 68% faradaic efficiency of acetate from CO with partial current density of 102 mA/cm2 was reached.

Reference

A. Dimian and A. Kiss, Chem. Eng. Res. Des., 159 (2020).

S. Guo, T. Asset, and P. Atanassov, ACS Catal., 5172–5188 (2021) https://pubs.acs.org/doi/abs/10.1021/acscatal.0c04862.

M. Jouny et al., Nat. Chem., 11, 846–851 (2019) https://doi.org/10.1038/s41557-019-0312-z.

W. Luc et al., Nat. Catal., 2, 423–430 (2019) https://doi.org/10.1038/s41929-019-0269-8.

Figure 1
(Invited) Flexible Electrosynthesis of Fuels and Chemicals at Intermediate Temperatures at Idaho National Laboratory
Authors: Ding Dong
Published: November 2022

Fuels and commodity chemicals make up a significant share of the potential energy savings opportunities for decarbonized economy and society. New innovative technologies are needed that can reduce the amount of energy and carbon intensity currently required to produce the key fuels and chemicals or associated building blocks. Electrochemistry is playing an increasingly important role in manufacturing as we reduce energy use and address uncertain supply chains driven by industrial electrification. In comparison to processes driven by heat and pressure, electrochemically-driven synthesis of fuels and chemicals provides unique opportunities for selective reactions and separations offering increased flexibility to manufacturing. As one of DOE’s premier multi-program energy research laboratories, Idaho National Laboratory’s (INL) mission is to ensure the nation’s energy security with safe, competitive and sustainable energy systems and unique national and homeland security capabilities. INL’s initiative, integrated energy systems (IES) provides carbon-free nuclear and renewable energy for downstream use in manufacturing and transportation. The manufacturing component of IES focuses on integrating clean, carbon-free electrons with waste/renewable heat and includes both manufacturing of electrochemical devices and implementing them in energy-efficient processes. In this talk, we will provide several examples for the pillar of energy to molecules and materials (E2M2) by utilizing the protonic ceramic electrochemical cells/membrane reactors (PCEC/PCEMR). The electrochemical route using PCEC/PCEMR offers a solution of process intensification and low carbon intensity. In addition to direct hydrogen production through water electrolysis at elevated temperatures, in situ use of hydrogen and protons with matching temperature for the industrial processes (e.g. Fischer Tropsch and Haber Bosch) has the advantage to leverage the existing infrastructures.
(Invited) Proton‐Conducting Solid Oxide Electrolysis Cells for Hydrogen Production - Materials Design and Catalyst Surface Engineering
Authors: Liu Xingbo , Tian Hanchen , Li Wenyuan
Published: November 2022

Solid oxide steam electrolysis cell, a promising electrical-chemical conversion device for the next generation efficient hydrogen production and energy storage, has been actively studied because of their high energy conversion efficiencies and prospective applications as electrochemical reactors. After decades of research on protonic ceramic materials, remarkable advances have been made in the protonic ceramic electrochemical cells (PCECs) air electrode and electrolyte. However, the existing air electrodes are far from satisfying the requirements of practical applications, a series of issues, including the lack of active and durable electrodes, greatly limit the commercialization. To date, the systematic development of triple conducting catalysts remains abstruse because of the challenges of characterizing protonic behavior. A quantitative properties assessment and prediction on protonic properties of perovskite are still not available.

Starting with a computational fluid dynamic modeling on the protonic ceramic electrochemical cells (PCECs) air electrode, we focused on the materials design of air electrode materials by employing model guidance, operating durability optimization by electrode structure engineering, as well as the air electrode surface tailoring to overcome the most rate-limiting step. Thus, the electrochemical performance and durability of PCEC care comprehensively improved. The fabrication methods, characterization techniques with electrochemical performance are presented. Further work plans and implications are proposed regarding optimizing the structure of materials, preparation technology, and better understanding the role of these triple conductors. This research is expected to provide an in-depth understanding and offer avenues in the rational design of PCEC with long operational life and high energy/power density in the near future.
(Invited) Selective CO2 Conversion in Protonic Ceramic Electrochemical Cells
Authors: Duan Chuancheng , Liu Fan
Published: November 2022

Protonic ceramic electrochemical cells (PCECs) are solid-state electrochemical devices that employ proton-conducting oxides as electrolytes, which offer a promising approach for electrification of chemical manufacturing, including CO2 reduction to produce value-added chemicals. The primary advantage of PCECs is their intermediate operating temperatures (300-600 °C), which thermodynamically and kinetically favor the CO2 reduction chemistry at the negative electrode. Unfortunately, the conventional negative electrode of PCECs, such as BaZr0.8-xCexY0.2O3-
𝛿-Ni or BaZr0.8-xCexY0.1Yb0.1O3-
𝛿-Ni, cannot reduce CO2 to either CH4 or CO with a selectivity of >99%, leading to the production of a mixture of CO and CH4. In this talk, we will present the rationally designed negative electrodes for CO2 conversion PCECs. The PCECs equipped with the new negative electrodes selectively favor the CO2-to-CO conversion. A selectivity of ~100% toward CO has been demonstrated over a wide range of operating temperatures (400-600 °C) and applied potential/current density. The negative electrode demonstrated in this work fully suppresses the CH4 production. In situ diffuse reflectance infrared spectroscopy (DRIFTS) was performed to probe the CO2 reduction mechanisms over the negative electrodes. This work validates that PCECs equipped with the rationally designed negative electrode can selectively manufacture chemicals.
Accelerated Discovery of Proton-Conducting Perovskites through Density Functional Theory and Machine Learning
Authors: Li Meng , Ding Dong
Published: November 2022

Hydrogen is an important energy carrier resource in response to limiting greenhouse gas emissions. Proton-conducting perovskite oxide is one of the key materials for highly efficient carbon-neutral hydrogen technologies, such as hydrogen production, CO2 hydrogenation, and ammonia synthesis. Many attempts have been made based on doped perovskites made of well-tested materials, such as BaZrO3, BaCeO3, BaHfO3, BaTiO3, and SrZrO3. However, the resulting perovskites have often suffered stability and conductivity problems. Furthermore, complex phenomena occurring during hydration present challenges for expanding the materials library. Herein, we demonstrate accelerated discovery of proton-conducting perovskites with high conductivity using machine learning (ML) predictions. We constructed consistent training data using density functional theory (DFT) which enable high accuracy of ML model. DFT computations were performed on > 1000 doped perovskite compositions to get their properties of lattice parameters, point defects (e.g., O vacancies, H interstitials), density of states, hydration energy, and proton migration energy. Several ML algorithms including Linear Regression, Bayesian Ridge Regression, Random Forest Regression, Neural networks, and k-Nearest Neighbor were tested for minimum errors and coefficient of determination. The multidimensional relationships between a set of >50 features and conductivity were mapped out using the optimized ML model. We screened a large material space of A-site and B-site doped perovskites to predict potential proton-conducting materials for various energy applications. The outcomes are promising for accelerating the design and applications of proton-conducting perovskite oxides in hydrogen technologies.
Influence of Imidazolium Pyrrole-2-Carbonitrile on the Electrochemical Reduction of CO2 on Silver Metal in Acetonitrile
Authors: Dongare Saudagar , Coskun Oguz Kagan , Wijesooriya Sanduni , Gurkan Burcu E
Published: November 2022

Electrochemical reduction of CO2 into value-added fuels or chemical feedstocks is one of several viable strategies for mitigating carbon dioxide waste. However, CO2 is thermodynamically stable molecule requiring high energy to activate it making this process energy demanding. Therefore, selective catalysts and stable electrolytes with high CO2 solubility are desired. Ionic liquids (ILs) are versatile solvents with tunable properties including high CO2 solubility and electrochemical stability. Literature suggests that ILs co-catalyze the CO2 reduction reaction and can alter the reaction route through its specific interactions with CO2 and reaction intermediates. Therefore, in this study, we examined the influence of 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]) IL on CO2 reduction in acetonitrile on Ag surface. [EMIM][2-CNpyr] has the carbene, N-heterocyclic, and amine functionalities to complex with CO2. The performed linear sweep voltammetry experiments shows the onset potential of CO2 reduction is -1.82 V (vs. Ag/Ag+) in the presence of the IL. This is confirmed to be due to the presence of the IL when compared to the control experiments with tetraethylammonium perchlorate which is a non-reactive supporting salt. The bulk electrolysis with 1.5 M [EMIM][2-CNpyr] in acetonitrile over Ag cathode showed reduction of CO2 to carbon monoxide (CO) with high selectivity (>80 %) at -2.1 V (vs. Ag/Ag+) and stable current density (~ 6 mA·cm−2) for at least 12 h without any electrolyte decomposition as confirmed by NMR analysis. The fundamental understanding of the interfacial microenvironment is needed and spectro-electrochemical studies are currently underway to probe these interfaces and to develop similarly high performing electrolytes for implementation of combined carbon capture and utilization in the future.
Interconnections between Solar-Driven Ammonia Production and the Water and Distribution Infrastructures at a Global Scale
Authors: Fernandez Carlos Arturo , Hatzell Marta
Published: November 2022

Ammonia plays a crucial role in the modern agriculture industry, as synthetic nitrogenous fertilizers supply over half of the nitrogen input into croplands. However, ammonia production through the Haber-Bosch process contributes to 1.2% of the global anthropogenic CO2 emissions and 2% of the global energy consumption. Thus, momentum has been building to transition Ammonia production towards renewable and electrified approaches. There are inherent risks and opportunities associated with the adoption of new technologies, and electrifying ammonia production will likely result in a new decentralized market for green ammonia. This work opens the dialogue to consciously create a system that is resilient, sustainable, and globally available.

This talk presents a detailed geospatial study on solar-driven ammonia production. First, we identify the spatial distribution of solar-driven ammonia production while considering key economic and performance parameters such as capital cost and energy efficiency. We study how the ammonia production cost distribution changes with the implementation of different technologies (i.e., low-temperature electrochemical ammonia production, lithium-mediated electrochemical ammonia production, and the electrified Haber-Bosch process). Then, we identify key considerations and performance targets (Energy Efficiency, Capital Costs, and Distribution Costs) for solar-driven ammonia production to reach economic feasibility. Finally, we optimize solar-driven ammonia production and distribution networks to decrease production and transportation costs while increasing resiliency towards changes in distribution costs and water scarcity through multi-objective network optimization.

Figure 1
Electrocatalytic Synthesis of Ammonia and Urea
Authors: Costa Figueiredo Marta
Published: November 2022

Many industrial chemical processes involve a high-energy demand (often still derived from fossil fuels), toxic reactants, and the production of high amounts of waste. A good example is the production of ammonia and urea via the Haber-Bosh and Bosch-Meiser processes, respectively. These two nitrogen-containing compounds are mostly used in the fertilizer industry and with the increase in the world population, their production is expected to increase. Additionally, NH3 itself is responsible for 2% of the annual world energy consumption and has a carbon footprint of 1.5 tons of CO2 per ton of NH3 [1]. Therefore, the development of more efficient, less hazardous technologies that are based on renewable energies to produce valuable N- containing compounds, has become one of the most challenging topics for chemical synthesis. By using electrochemical methods for the synthesis of ammonia and urea, toxic and dangerous chemicals can be replaced with clean electrons. Furthermore, the efficiency and selectivity of the reactions can be tuned by the applied potential, and more importantly, the energy used can come from renewable sources like wind or solar [2].

In this talk, I will show the recent advances from our group in the development of catalysts for the electrocatalytic synthesis of ammonia and urea (as for example Cu2O and CuRh) and the reaction mechanism when using nitrate as a substrate [3].

References:

[1] S. Giddey, et al, Int. J. Hydrogen Energy, 38 (2013) 14576–14594

[2] Frontana-Uribe, B. A. et al; Green Chem. 2010, 12 (12) 2099– 2119

[3] D. Anastasiadou, Y. van Beek, M. C. Figueiredo, in preparation.

Figure 1: SEM images of two electrodeposited electrocatalysts used for ammonia and urea electrosynthesis from nitrates: a) CuRh and b) CuO.

Figure 1
Tunning Copper Sulfide Nanocatalysts for an Efficient Electrochemical Nitrogen Reduction
Authors: Jin Haneul , Choi Jihyun , Kim Seung-hoon , Park Hyun S. , Yoo Sung Jong
Published: November 2022

Electrocatalytic performance depends on the surface characteristics of catalysts. Understanding the determinants for adsorption of the reactants and desorption of the products is essential for efficient electrocatalyst design. Electrochemical nitrogen reduction (eNRR) is initiated by nitrogen adsorption and is progressed by hydrogenation to produce ammonia. Despite the intensive development of eNRR catalysts, optimum catalyst design for eNRR is barely understood. Here, we report a designer approach study for investigating the relationship between catalyst surface features (surface geometry and composition) and eNRR performances. To test our idea, facet-controlled copper sulfide hexagonal nanoprisms which only expose two types of facets, {100} and {010}, were deliberately prepared. We studied exposed facet density-dependent eNRR performances by controlling aspect ratios of the Cu1.81S nanoprisms. Thereafter, we tested surface dopant effects on eNRR activity and stability by introducing heteroatoms on the Cu1.81S nanoprisms. Physical and electrochemical properties of the catalysts were investigated by TEM, CV, and DFT analyses and it is discovered that protruded surfaces are active for the eNRR and dopant enhances the eNRR performances.

References

Zhao, X.; Hu, G.; Chen, G. F.; Zhang, H.; Zhang, S.; and Wang, H., Mater, 33, 2007650 (2021).

Kim, H. S.; Choi, J.; Kong, J.; Kim, H.; Yoo, S. J.; and Park, H. S., ACS Catal. 11, 435 (2020).