Increasing the electrode thickness, thereby reducing the proportion of inactive cell components, is one way to achieve higher-energy- density lithium-ion batteries. This, however, results in higher electronic and ionic overpotentials and/or mechanical failure induced by binder migration. Here, we report ethanol-induced phase inversion as an effective method for making high-mass-loading nickel- rich, layered oxide (LiNi0.8Mn0.1Co0.1O2 0.8 Mn 0.1 Co 0.1 O 2 [NMC811]) electrodes. The ethanol-induced phase inversion electrodes significantly outperform their conventionally processed counterparts with similar loading (35 mg/cm2) 2 ) and porosity (30%) in Li/NMC half-cells (131.7 mAh/g vs. 56.7 mAh/g) at 1C (7 mA/cm2) 2 ) discharge. The binder structure induced by the nonsolvent improves the pore connectivity and results in lower tortuosity factors. The rapid solvent removal reduces the binder migration during drying, enabling ultrahigh active mass loadings up to 60 mg/cm2 2 (12 mAh/cm2). 2 ). Further, the compatibility of the phase inversion process with current roll-to-roll coating setups makes this a processing technique with high industrial feasibility.

Invited for this month's cover is the group of Prof. Fokko M. Mulder at the Delft University of Technology. The image on the cover shows how in the NH3 synthesis via hydrogen-permeable electrode the N, H species on the catalyst surface can be controlled, using the analogy of a traffic controller. The Research Article itself is available at 10.1002/cssc.202300460.

The electrochemical dinitrogen reduction reaction (NRR) has recently gained much interest as it can potentially produce ammonia from renewable intermittent electricity and replace the Haber-Bosch process. Previous literature studies report Fe- and Mo-carbides as promising electrocatalysts for the NRR with activities higher than other metals. However, recent understanding of extraneous ammonia and nitrogen oxide contaminations have challenged previously published results. Here, we critically assess the NRR performance of several Fe- and Mo-carbides reported as promising by implementing a strict experimental protocol to minimize the effect of impurities. The successful synthesis of α-Mo2C decorated carbon nanosheets, α-Mo2C nanoparticles, θ-Fe3C nanoparticles, and χ-Fe5C2 nanoparticles was confirmed by X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron and Mössbauer spectroscopy. After performing NRR chronoamperometric tests with the synthesized materials, the ammonia concentrations varied between 37 and 124 ppb and are in close proximity with the estimated ammonia background level. Notwithstanding the impracticality of these extremely low ammonia yields, the observed ammonia did not originate from the electrochemical nitrogen reduction but from unavoidable extraneous ammonia and NO x impurities. These findings are in contradiction with earlier literature studies and show that these carbide materials are not active for the NRR under the employed conditions. This further emphasizes the importance of a strict protocol in order to distinguish between a promising NRR catalyst and a false positive.

Electrochemical reduction of CO 2 presents an attractive way to store renewable energy in chemical bonds in a potentially carbon-neutral way. However, the available electrolyzers suffer from intrinsic problems, like flooding and salt accumulation, that must be overcome to industrialize the technology. To mitigate flooding and salt precipitation issues, researchers have used super-hydrophobic electrodes based on either expanded polytetrafluoroethylene (ePTFE) gas-diffusion layers (GDL’s), or carbon-based GDL’s with added PTFE. While the PTFE backbone is highly resistant to flooding, the non-conductive nature of PTFE means that without additional current collection the catalyst layer itself is responsible for electron-dispersion, which penalizes system efficiency and stability. In this work, we present operando results that illustrate that the current distribution and electrical potential distribution is far from a uniform distribution in thin catalyst layers (~50 nm) deposited onto ePTFE GDL’s. We then compare the effects of thicker catalyst layers (~500 nm) and a newly developed non-invasive current collector (NICC). The NICC can maintain more uniform current distributions with 10-fold thinner catalyst layers while improving stability towards ethylene (≥ 30%) by approximately two-fold.

The Front Cover shows how in the NH3 synthesis via a hydrogen-permeable electrode the N, H species on the catalyst surface can be controlled, using the analogy of a traffic controller. In this work, the authors investigated the effect of temperature and H permeation flux on the NH3 synthesis process. Increasing operating temperature improves the NH3 synthesis activity, efficiency and stability, thanks to the enhanced nitrogen adsorption and NH3 desorption. Stable and efficient nitrogen reduction reactivity is achieved with a critical control over the population of N, NHx, and H species at the catalyst surface. More information can be found in the Research Article by D. Ripepi et al.

Ammonia (NH3) ranks among the largest bulk chemical products in the world, with an annual production of 178 million tons and an estimated annual market growth of 3−5% to meet the global demand for fertilizer in the agricultural sector due to an increasing world population. The majority of NH3 is produced by the Haber−Bosch process, wherein elevated temperatures (300−500 °C) and pressures (200−300 bar) are required. In addition, the current process has a major environmental impact (∼1% of the global greenhouse emissions), mostly due to the production of hydrogen by steam-methane reforming. To meet the net-zero emissions goal by 2050, as established in the latest IPCC report, ammonia must be produced via a sustainable pathway. Direct electrocatalytic synthesis of ammonia from dinitrogen and water at mild conditions could potentially offer a carbon-free alternative, resilient to intermittent renewable energy generation. Despite the large research efforts on nitrogen electroreduction in aqueous electrolytes, current NH3 synthesis rates remain extremely low (0.003−14 nmol cm−2 s−1). This is mainly due to the lack of a suitable electrocatalyst and competition with the hydrogen evolution reaction (HER). Besides, the reliable quantification of these low ammonia yields has raised several concerns in the scientific community. The presence of trace amounts of extraneous N species (such as, NH3, NOx, N2O, NOx, and other, more labile forms of N) has led to an increasing number of reported false positives and non-reproducible results. Overall, the electrochemical reduction of nitrogen oxide species into ammonia is more facile than the nitrogen reduction reaction (NRR) on many transition metals. An exception is N2O, which has been proven to only electroreduce into N2 on several transition metals. This implies that N2O is not a concerning impurity source for the NRR. Numerous rigorous experimental protocols have been proposed to perform reliable quantification of NH3 produced by electrochemical N2 reduction. 18,19

Higher energy density Li-ion batteries that can enable longer driving ranges are currently subject to intensive research interest. Increasing the thickness of electrodes and reducing the proportion of inactive components per cell is one way to achieve this. In thick electrodes, a higher electronic and ionic overpotential and mechanical failure (cracking, delamination etc.) induced by binder migration during the drying process leads to sluggish (dis)charge performance or even cell failure respectively. Here we report non-solvent induced phase inversion as a scalable, effective method to arrive at thick NMC811 electrodes. By tuning the non-solvent properties and other processing conditions to be compatible with Ni-rich electrodes, it was possible to obtain NMC811 electrodes with mass loadings up to 11 mAh/cm2 (single sided) which outperform their conventional processed counterparts in Li/NMC half cells. This improvement could be attributed to the altered carbon-binder structure, which improves the pore connectivity and lowers the electrode tortuosity factor. The rapid solvent removal also reduces the long-range binder migration during drying. With imaging and porosimetry techniques we show the structural change which leads to the observed improved electrochemical performance. The method also shows good compatibility with double sided slot-die electrode coating procedure, making this a technique with potentially high industrial feasibility towards making thicker NMC811 and other electrodes.

The electrochemical CO 2 reduction reaction (CO 2 RR) is an attractive method to produce renewable fuel and chemical feedstock using clean energy sources. Formate production represents one of the most economical target products from CO 2 RR but is primarily produced using post‐transition metal catalysts that require comparatively high overpotentials. Here a composition of bimetallic Cu–Pd is formulated on 2D Ti 3 C 2 T x (MXene) nanosheets that are lyophilized into a highly porous 3D aerogel, resulting in formate production much more efficient than post‐transition metals. Using a membrane electrode assembly (MEA), formate selectivities >90% are achieved with a current density of 150 mA cm −2 resulting in the highest ever reported overall energy efficiency of 47% (cell potentials of −2.8 V), over 5 h of operation. A comparable Cu‐Pd aerogel achieves near‐unity CO production without the MXene templating. This simple strategy represents an important step toward the experimental demonstration of 3D‐MXenes‐based electrocatalysts for CO 2 RR application and opens a new platform for the fabrication of macroscale aerogel MXene‐based electrocatalysts.

Proton Exchange Membrane Water Electrolysis (PEMWE) is a commercial technology with specific advantages such as high-power density and rapid start-up times, which makes it a perfect match to produce hydrogen from intermittent renewable energy sources (green H2). [1] However, very scarce materials, such as iridium and platinum, are currently used as catalysts and protection coatings to withstand the harsh operating conditions in PEMWE. Iridium is the anode catalyst in the state-of-the-art PEMWE, with loadings in the range 1-2 mg/cm2. This metric translates into using 200-500 kg of iridium per GW, which accounts for roughly 10% of the global iridium production per year. Reducing iridium usage in PEMWE is critical to realize the 10-100 GW/year growth in green H2 power. [2,3] To significantly reduce the Ir loading, while maintaining the lateral conductivity, we coated the iridium catalyst by atmospheric spatial Atomic Layer Deposition (sALD) on titanium porous transport layer (PTL), which acts as the electrically conductive substrate. The coating renders ultra-low iridium loadings, which is 100-200 times less iridium than the state-of-the-art catalyst coated membrane technology, while retaining ca. 60-80% of the performance (in terms of current density), with durability demonstrated up to 100 h (see Figure 1). We will also show here that protection coatings on the titanium PTL are beneficial to yield good durability with these ultra-low loadings of iridium and demonstrated that sALD has the potential to produce non-PGM based protection coatings. [1] Barbir, F. Solar Energy 78 (2005) 661-669. [2] Gavrilova, A., Wieclawska, S.M. “Towards a green future. Part 2” (2021). TNO report 21-12158. [3] Minke, C., Suermann, M., Bensmann, B., & Hanke-Rauschenbach, R. J. Hydrogen Energy 46 (2021) 23581-23590. Figure 1

Continued advancements in the electrochemical reduction of CO2 (CO2RR) have emphasized that reactivity, selectivity, and stability are not explicit material properties but combined effects of the catalyst, double-layer, reaction environment, and system configuration. These realizations have steadily built upon the foundational work performed for a broad array of transition metals performed at 5 mA cm(-2), which historically guided the research field. To encompass the changing advancements and mindset within the research field, an updated baseline at elevated current densities could then be of value. Here we seek to re-characterize the activity, selectivity, and stability of the five most utilized transition metal catalysts for CO2RR (Ag, Au, Pd, Sn, and Cu) at elevated reaction rates through electrochemical operation, physical characterization, and varied operating parameters to provide a renewed resource and point of comparison. As a basis, we have employed a common cell architecture, highly controlled catalyst layer morphologies and thicknesses, and fixed current densities. Through a dataset of 88 separate experiments, we provide comparisons between CO-producing catalysts (Ag, Au, and Pd), highlighting CO-limiting current densities on Au and Pd at 72 and SO mA cm(-2), respectively. We further show the instability of Sn in highly alkaline environments, and the convergence of product selectivity at elevated current densities for a Cu catalyst in neutral and alkaline media. Lastly, we reflect upon the use and limits of reaction rates as a baseline metric by comparing catalytic selectivity at 10 versus 200 mA cm(-2). We hope the collective work provides a resource for researchers setting up CO2RR experiments for the first time.

The nitrogen reduction reaction (NRR) is a promising pathway toward the decarbonization of ammonia (NH3) production. However, unless practical challenges related to the detection of NH3 are removed, confidence in published data and experimental throughput will remain low for experiments in aqueous electrolyte. In this perspective, we analyze these challenges from a system and instrumentation perspective. Through our analysis we show that detection challenges can be strongly reduced by switching from an H-cell to a gas diffusion electrode (GDE) cell design as a catalyst testing platform. Specifically, a GDE cell design is anticipated to allow for a reduction in the cost of crucial N-15(2) control experiments from (sic)100-2000 to less than (sic)10. A major driver is the possibility to reduce the N-15(2) flow rate to less than 1 mL/min, which is prohibited by an inevitable drop in mass-transport at low flow rates in H-cells. Higher active surface areas and improved mass transport can further circumvent losses of NRR selectivity to competing reactions. Additionally, obstacles often encountered when trying to transfer activity and selectivity data recorded at low current density in H-cells to commercial device level can be avoided by testing catalysts under conditions close to those in commercial devices from the start.

The electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the current greenhouse-gas-emission intensive process to produce ammonia (NH3) from nitrogen (N2). However, finding an electrocatalyst that promotes NRR over the competing hydrogen evolution reaction (HER) has proven to be difficult. This difficulty could potentially be addressed by accelerating the electrocatalyst development for NRR by orders of magnitude using high-throughput (HTP) workflows. In this work, we developed a HTP gas diffusion electrode (GDE) cell to screen up to 16 electrocatalysts in parallel. The key innovation of the cell is the use of expanded Polytetrafluoroethylene (ePTFE) gas diffusion layers (GDL) which simplifies the handling of catalyst arrays compared to carbon fabrics and enables sufficient N2 mass transport. We demonstrate the robustness of the HTP workflow by screening 528 bimetallic catalysts of composition AB (A,B = Ag, Al, Au, Co, Cu, Fe, Mn , Mo, Ni, Pd, Re, Ru, W) for NRR activity. None of the materials produced ammonia significantly over background level which emphasizes the difficulty of finding active electrocatalysts for NRR and narrows down the search space for future studies.

Ammonia is an energy-rich molecule, primarily used as fertiliser and produced at large scale via the intensive Haber-Bosh process, which is responsible for 1-2% of the CO2 emitted globally.1 In recent years, the electroreduction of N2 to ammonia registered a bursting interest, motivated by the urgent necessity to meet the fast-growing demand for carbon neutral fertilisers and sustainable fuels. However, ammonia synthesis in conventional electrochemical aqueous electrolyte systems is facing serious challenges, such as the competing hydrogen evolution reaction that regularly prevails during electrocatalysis. Herein we propose a strategy to decouple the hydrogen generation from the activation and hydrogenation of nitrogen (Figure 1). Atomic hydrogen is electrochemically generated from water reduction and inserted in the nickel electrode/membrane lattice. The dense metallic electrode provides a selective and controlled access of protons and electrons to the nitrogen active site, while ensuring a complete separation from the electrolyte. Our results demonstrate the unprecedented hydrogenation reaction of activated surface nitrogen to ammonia by electrochemical permeating atomic hydrogen. Ammonia synthesis and quantification were carried out following rigorous protocols and control experiments, including careful check of contamination level, purification of feed gases and 15N2 experiments. A gas chromatography method was developed to continuously detect in situ the produced ammonia, with a limit of quantification of 150 ppb.2 Quantitative 15N labelling experiments confirm that ammonia is produced directly in the gas phase at room temperature and atmospheric pressure from gaseous N2. Experimental observations reveal that the presence of N-vacancies, formed upon the hydrogenation of surface nitrides, plays a key role in the catalytic process facilitating gaseous nitrogen adsorption via a Mars-van Krevelen mechanism. This work provides an alternative pathway for the development of an efficient direct electrolytic ammonia production at ambient conditions from water, nitrogen and renewable electricity. We are currently extending our knowledge on the reaction mechanisms and considerably improving the systems performances. Preliminary results reveal that the formation of nitrogen vacancies via electrochemical hydrogen permeation at 100 C and atmospheric pressure enables a direct hydrogenation process, in which H2, N2 and N-vacancies react to form NH3 at conditions otherwise not favourable to ammonia synthesis. In this talk our latest progress on ammonia synthesis via electrochemical permeating hydrogen will be reviewed. References D. R. MacFarlane, P. V. Cherepanov, J. Choi, B. H. R. Suryanto, R. Y. Hodgetts, J. M. Bakker, F. M. Ferrero Vallana and A. N. Simonov, Joule, 2020, 4, 1186-1205. R. Zaffaroni, D. Ripepi, J. Middelkoop and F. M. Mulder, ACS Energy Letters, 2020, 5, 3773-3777. D. Ripepi, R. Zaffaroni, H. Schreuders, B. Boshuizen and F. M. Mulder, ACS Energy Letters, 2021, DOI: 10.1021/acsenergylett.1c01568, 3817-3823. Figure 1

The electrochemical reduction of carbon dioxide (CO2) to value-added materials has received considerable attention. Both bulk transition-metal catalysts and molecular catalysts affixed to conductive noncatalytic solid supports represent a promising approach toward the electroreduction of CO2. Here, we report a combined silver (Ag) and pyridine catalyst through a one-pot and irreversible electrografting process, which demonstrates the enhanced CO2 conversion versus individual counterparts. We find that by tailoring the pyridine carbon chain length, a 200 mV shift in the onset potential is obtainable compared to the bare silver electrode. A 10-fold activity enhancement at -0.7 V vs reversible hydrogen electrode (RHE) is then observed with demonstratable higher partial current densities for CO, indicating that a cocatalytic effect is attainable through the integration of the two different catalytic structures. We extended the performance to a flow cell operating at 150 mA/cm2, demonstrating the approach's potential for substantial adaptation with various transition metals as supports and electrografted molecular cocatalysts.

Hydrogen permeable electrodes can be utilized for electrolytic ammonia synthesis from dinitrogen, water, and renewable electricity under ambient conditions, providing a promising route toward sustainable ammonia. The understanding of the interactions of adsorbing N and permeating H at the catalytic interface is a critical step toward the optimization of this NH3 synthesis process. In this study, we conducted a unique in situ near ambient pressure X-ray photoelectron spectroscopy experiment to investigate the solid-gas interface of a Ni hydrogen permeable electrode under conditions relevant for ammonia synthesis. Here, we show that the formation of a Ni oxide surface layer blocks the chemisorption of gaseous dinitrogen. However, the Ni 2p and O 1s XPS spectra reveal that electrochemically driven permeating atomic hydrogen effectively reduces the Ni surface at ambient temperature, while H2 does not. Nitrogen gas chemisorbs on the generated metallic sites, followed by hydrogenation via permeating H, as adsorbed N and NH3 are found on the Ni surface. Our findings suggest that the first hydrogenation step to NH and the NH3 desorption might be limiting under the operating conditions. The study was then extended to Fe and Ru surfaces. The formation of surface oxide and nitride species on iron blocks the H permeation and prevents the reaction to advance; while on ruthenium, the stronger Ru-N bond might favor the recombination of permeating hydrogen to H2 over the hydrogenation of adsorbed nitrogen. This work provides insightful results to aid the rational design of efficient electrolytic NH3 synthesis processes based on but not limited to hydrogen permeable electrodes.

Direct electrochemical nitrogen reduction holds the promise of enabling the production of carbon emission-free ammonia, which is an important intermediate in the fertilizer industry and a potential green energy carrier. Here we show a strategy for ambient condition ammonia synthesis using a hydrogen permeable nickel membrane/electrode that spatially separates the electrolyte and hydrogen reduction side from the dinitrogen activation and hydrogenation sites. Gaseous ammonia is produced catalytically in the absence of electrolyte via hydrogenation of adsorbed nitrogen by electrochemically permeating atomic hydrogen from water reduction. Dinitrogen activation at the polycrystalline nickel surface is confirmed with 15N2 isotope labeling experiments, and it is attributed to a Mars-van Krevelen mechanism enabled by the formation of N-vacancies upon hydrogenation of surface nitrides. We further show that gaseous hydrogen does not hydrogenate the adsorbed nitrogen, strengthening the benefit of having an atomic hydrogen permeable electrode. The proposed approach opens new directions toward green ammonia.

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTGas Chromatographic Method for In Situ Ammonia Quantification at Parts per Billion LevelsRiccardo ZaffaroniRiccardo ZaffaroniMaterials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The NetherlandsMore by Riccardo Zaffaroni, Davide RipepiDavide RipepiMaterials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The NetherlandsMore by Davide Ripepi, Joost MiddelkoopJoost MiddelkoopMaterials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The NetherlandsMore by Joost Middelkoop, and Fokko M. Mulder*Fokko M. MulderMaterials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands*[email protected]More by Fokko M. Mulderhttp://orcid.org/0000-0003-0526-7081Cite this: ACS Energy Lett. 2020, 5, 12, 3773–3777Publication Date (Web):November 12, 2020Publication History Received16 October 2020Accepted27 October 2020Published online12 November 2020Published inissue 11 December 2020https://doi.org/10.1021/acsenergylett.0c02219Copyright © Published by American Chemical Society 2020RIGHTS & PERMISSIONSACS AuthorChoicewith CC-BY-NC-NDlicenseArticle Views9295Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Ammonia,Chromatography,Gases,Liquids,Nitrogen Get e-Alerts

Rapid advances in electrocatalytic ammonia synthesis are impeded by laborious detection methods commonly used in the field and by constant risk of external contaminations, which generates misleading false positives. We developed a facile real-time GC-MS method for sensitive isotope NH3 quantification, requiring no external sample manipulations. This method ensures high detection reliability paramount to accelerate (electro-)catalyst screening.