Ionic liquids are tunable solvents composed entirely of ions that have properties desirable as electrolytes for lithium batteries such as nonflammability and a large electrochemical stability window. Solvate ionic liquids are a subclass of ionic liquids that consist of a glyme-based solvent and lithium salt in an equimolar ratio, where Li+ cation-glyme solvation interactions result in ionic liquid-like properties. LiG4TFSI is a well-studied solvate ionic liquid consisting of equimolar amounts of lithium bis-(trifluoromethylsulfonyl)-imide (LiTFSI) and tetraglyme (G4). In this work, pyrrolidinium ionic liquids with ether-functionalized side chains were synthesized, containing either one ether (EO1) moiety or three ether (EO3) moieties and mixed with LiG4TFSI to form a new class of electrolyte mixtures. Their physical and transport properties, as well as ion solvation structures, were characterized by electrochemical, thermal, rheological, and spectroscopic measurements. The conductivity of the electrolyte mixture composed of EO1:LiTFSI:G4 in a 1:1:1 molar ratio is 2.54 mS/cm at 30 °C, compared to 1.53 mS/cm for LiG4TFSI, an increase of 67%. A significant decrease in the conductivity to 0.279 mS/cm is observed for the EO3:LiTFSI:G4 mixture in a 1:1:0.4 molar ratio. Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) measurements revealed that the EO1 cation diffuses significantly faster than the EO3 cation in their respective mixtures. Liquid-state 13C NMR experiments indicate that Li+ cations preferentially coordinate with tetraglyme. Li+ cations do not coordinate with the EO1 cation and coordinate with the EO3 ether side chains only at lower concentrations of tetraglyme. We hypothesize that the oligoether EO3 cation competes with G4 and TFSI- for lithium cation solvation in G4-deficient compositions, leading to a largely adverse effect on the mass transport properties of the electrolyte.

The electrode geometry significantly influences the selectivity and activity in CO2 electroreduction (CO2ER) even when the same materials are utilized. In order to obtain insight into why the electrode geometry impacts the CO2ER, a computational study using COMSOL Multiphysics software was conducted. A three-dimensional (3-D) simulation was performed to compare three electrodes with the same surface area (0.9 cm(2)) and different geometries: a two-dimensional (2-D) flag, a 3-D foil coil, and a 3-D wire coil, all composed of silver. The results showed that the edges and corners have a higher current density and stronger electric field compared with the flat regions. Therefore, the foil coil and wire coil, which have more edges and corners compared to the flag, had a higher total current, a stronger electric field, and a more uniform current distribution on the surface. The high current at the edges and corners can decrease the energy barrier needed for CO2ER. An enhanced electric field can also increase the concentration of cations at the interface, leading to stabilization of the intermediates such as CO2 center dot- radicals and improvement in CO2ER. The interfacial properties in the electrode-electrolyte interface are also impacted by the electrode geometry. It was also observed that the edges and corners have a higher local pH and a lower CO2 concentration due to the enhanced CO2ER reactions at these sharp points. The calculations in this study can further explain the enhanced performance of foil coil and wire coil electrodes, which had been observed in our previous report. This work illustrates how important it is to include electric field and current distribution considerations in the design of electrochemical reactors.

There is a significant opportunity to improve the sustainability of chemical manufacturing through the pairing of biomass-derived feedstocks with renewable electricity driven processes. Furanics are promising platform chemicals that can be applied to a broad range of chemical and fuel products. Both furfural and HMF can be electrochemically reduced through hydrogenation or hydrogenolysis using copper electrocatalysts. One of the main challenges that needs to be overcome is the control of selectivity to desired products when multiple products are possible from both the electrochemistry and the homogeneous side reactions in the electrolyte. A better mechanistic understanding of the electrochemical and homogeneous reactions is necessary to enable selectivity control. Utilizing microkinetic models fed from bulk electrolysis, in situ FTIR experiments and characterization of copper electrodes after electrochemical reaction, we have been able to elucidate pH-dependent mechanisms for the electroreduction of furfural. Learnings have been extended to HMF as well.

Hydrogen (H2) has been proposed as a way to store energy for long durations with minimal carbon footprint. The challenges of using H2 to store energy are that it has very low volumetric density and diffuses rapidly through container walls. Liquid organic hydrogen carriers (LOHCs) have been proposed as a method of storing hydrogen in the molecular backbone of stable organic chemicals, addressing many of the concerns of molecular hydrogen. The majority of LOHC systems proposed have utilized thermochemical cycling for the hydrogenation (to store hydrogen) and dehydrogenation (to release hydrogen). Thermochemical cycling requires heating of the reactors, which results in an increased carbon footprint, and is not easily amenable to dynamic operating with the variable renewable electricity grid. Electrochemical LOHC cycling has been proposed as an alternative to thermochemical cycling because it can pair directly with the variable renewable grid and operate more dynamically. To understand the viability of the thermochemical and electrochemical processes, a comparative carbon footprint analysis is necessary. The analysis showed that the electrochemical LOHC cycling process achieves the lowest carbon footprint when using highly concentrated LOHCs as the feed or when a downstream separation process was not needed. The carbon footprint in electrochemical cycling of diluted LOHC was primarily contributed to by the LOHC distillation separation process. A sensitivity analysis showed the carbon footprint LOHC concentration dependence during the electrochemical cycling process. Moreover, the electrolyte composition significantly affects the carbon footprint during electrochemical LOHC cycling. Decisions regarding use of thermochemical versus electrochemical cycling need to include separation system boundaries, not just the reactors themselves.

Rechargeable aluminum (Al) metal batteries are enticing for the coming generation of electrochemical energy storage systems due to the earth abundance, high energy density, inherent safety, and recyclability of Al metal. However, few electrolytes can reversibly electrodeposit Al metal, especially at low temperatures. In this study, Al electroplating and stripping were investigated from 25 degrees C to -40 degrees C in mixtures of aluminum chloride (AlCl3), 1-ethyl-3-methyl-imidazolium chloride ([EMIm]Cl), and urea. The ternary ionic liquid analogue (ILA) consisting of AlCl3-urea-[EMIm]Cl in a molar ratio of 1.3:0.25:0.75 enabled reversible Al electrodeposition at temperatures as low as -40 degrees C while exhibiting the highest current density and the lowest overpotential among all of the electrolyte mixtures at 25 degrees C, including the AlCl3-[EMIm]Cl binary mixture. The ILA electrolyte was further tested in a rechargeable Al-graphite battery system down to -40 degrees C. The addition of urea to AlCl3-[EMIm]Cl binary mixtures can improve the Al electrodeposition, extend the liquid temperature window, and reduce the cost.

Li-ion batteries are commonly used as electrochemical energy storage systems due to their high energy density. However, few Li-ion batteries can reliably function at elevated temperatures, which is necessary for space and defense applications. In this study, Li-ion electrolytes were prepared and investigated for use at 100 degrees C. The previously developed baseline electrolyte, 1.0 M lithium hexafluorophosphate (LiPF6) in 1:1 ethylene carbonate (EC):ethyl-methyl carbonate (v/v) with 2 wt% vinylene carbonate (VC), was altered to observe the effects of the lithium salts lithium difluoro(oxalato)borate (LiDFOB) and lithium difluorophosphate (LiDFP), and the fluorinated co-solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). The resulting formulations showed significantly improved capacity retention at 100 degrees C in multiple cell configurations. X-ray photoelectron spectroscopy characterization of the electrodes following cycling at high temperatures with the improved electrolyte revealed the cathode-electrolyte-interface to be boron-rich, while the graphite anodes were found to have little boron but were more fluorine rich compared to the baseline anodes. Raman spectroscopy determined notable changes in solvation structure upon addition of the TTE diluent. Overall, the use of various Li salts as well as the TTE co-solvent improved specific capacity retention at 100 degrees C in Li-ion cells.

Electrification to reduce or eliminate greenhouse gas emissions is essential to mitigate climate change. However, a substantial portion of our manufacturing and transportation infrastructure will be difficult to electrify and/or will continue to use carbon as a key component, including areas in aviation, heavy-duty and marine transportation, and the chemical industry. In this Roadmap, we explore how multidisciplinary approaches will enable us to close the carbon cycle and create a circular economy by defossilizing these difficult-to-electrify areas and those that will continue to need carbon. We discuss two approaches for this: developing carbon alternatives and improving our ability to reuse carbon, enabled by separations. Furthermore, we posit that co-design and use-driven fundamental science are essential to reach aggressive greenhouse gas reduction targets. To achieve net-zero carbon emissions, we must close the carbon cycle for industries that are difficult to electrify. Developing the needed science to provide carbon alternatives and non-fossil carbon will accelerate advances towards defossilization.

Rechargeable aluminum (Al) metal batteries are an emerging energy storage technology ideal for use at a global scale: Al metal is energy dense, low cost, inherently safe, earth abundant, and highly recyclable. Despite such great promise, their technological progress has been hindered by the few electrolytes able to reversibly electrodeposit Al metal at room temperature, coupled with the limited number of positive electrode materials that are compatible with them. In this context, recent progress will be discussed in the development of electrolyte mixtures and organic cathode materials for rechargeable aluminum batteries. Chloroaluminate ionic liquid electrolytes and ionic liquid analogues prepared using mixtures of organic cations and/or neutral solvent species will be presented, which exhibit improved electrochemical properties for aluminum electrodeposition and in aluminum-graphite batteries, over temperatures ranging from ambient conditions down to -60 °C. Different organic structures will also be presented as organic cathode materials for aluminum batteries, where the effects of molecular structure on bulk energy storage properties will be discussed. Molecular-scale understanding of their ionic and electronic charge storage mechanisms will be elucidated through a combination of solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations. Lastly, by using different electrolytes in combination with an organic cathode, it will be shown that electrolyte speciation can affect the local environments of charge-compensating ions in cycled organic electrodes. Overall, the results and analyses are aimed at developing next-generation rechargeable aluminum metal batteries for diverse energy storage applications.

The chemical industry is a major source of economic productivity and employment globally and among the top 3 industrial sources of greenhouse gas (GHG) emissions, along with steel and cement. As global demand for chemical products continues to grow, there is an urgency to develop and deploy sustainable chemical produc-tion pathways and to reconsider continued investment in current emission-intensive production technologies. This perspective de-scribes the challenges and opportunities to decarbonize the chemi-cal industry via electrification powered by low-carbon electricity supply, both in the near term and long term, and it discusses four technological pathways ranging from the more mature direct substi-tution of heat with electricity and use of hydrogen to technologically less mature, yet potentially more selective, approaches based on electrochemistry and plasma. Finally, we highlight the key elements of integrating an electrified industrial process with the power sector to leverage process flexibility to reduce energy costs of chemical production and provide valuable power grid support services. Un-locking such plant-to-grid coordination and the four electrification pathways has significant potential to facilitate rapid and deep de-carbonization of the chemical industry sector.

CO 2 emissions are generated in the chemical industry by factors such as the generation of reactants, including hydrogen, as well as in heating of the reactors. Electrochemical methods can avoid the need for externally provided hydrogen by generating required protons in-situ from the electrolyte, and can be more easily coupled with renewable electricity than their thermocatalytic counterparts. Therefore, to assist in the mitigation of CO 2 emissions, electrochemical processes can be used. Furfural is a biomass-derived platform molecule that can be electrochemically reacted to form several species of interest including fine chemicals and fuels. Furfuryl alcohol, the hydrogenation product, is one fine chemical of interest used to make furanic molds or resins. The hydrogenolysis product of furfural, 2-methylfuran, has been identified as a fuel additive. The electrochemical hydrogenation and hydrogenolysis over Cu catalysts in acidic media allows for the parallel production of furfuryl alcohol and 2-methylfuran. During the electrochemical hydrogenation and hydrogenolysis of furfural over Cu in acidic electrolyte, the Cu catalyst will become covered in carbonaceous material with use. This fouling changes with applied potential, with a polymeric material being formed at -560 mV RHE while at -700mV a non-polymeric carbonaceous material is formed on the Cu. In both cases, the fouling leads to deactivation of the catalyst. In this work, Cu metal foils were intentionally fouled to study the mechanisms that led to catalyst fouling to provide insights into possible mitigation techniques. A semi batch reactor was used in which the Cu working electrode was recycled to further foul the catalyst. The catholyte had 200 mM furfural and 0.5 M H 2 SO 4 in a 80:20 vol% water:acetonitrile co-solvent. The Cu electrode was recycled thrice with fresh electrolytes each time. After use at -560 mV RHE a polymer formed on the surface; FTIR of the fouled surface showed consistent spectra as poly(furfuryl alcohol). At -700 mV RHE, no polymer was found, however a carbonaceous layer was found. XPS was used to better distinguish between the carbonaceous fouling that occurred at different applied potentials.

CO2 electroreduction (CO2ER) by using renewableenergyresources is a promising method to mitigate the CO2 levelin the atmosphere as well as produce valuable chemicals. Local environmentat the electrode-electrolyte interface plays a key role inCO2ER activity and selectivity along with its competing hydrogen evolutionreaction (HER). In addition to the catalyst and reactor design, electrolytealso has a significant impact on the interface. Herein, electrolyteadditives were used to modify the local environment around the Cucatalyst during CO2ER. For this purpose, 10 mM ionic additives withbis-(trifluoromethylsulfonyl)-imide ([NTF2](-)) and dicyanamide ([DCA](-)) as anions and 1-butyl-3-methylimidazolium([BMIM](+)), potassium (K+), or sodium (Na+) as cations have been added to an aqueous potassium bicarbonatesolution (0.1 M KHCO3). COMSOL Multiphysics was also usedto calculate the local pH and CO2 concentration at theelectrode-electrolyte interface in different electrolytes.Results showed that the local environment modifications by the electrolyteadditives altered the activity and selectivity of Cu in CO2ER. Itwas found that the CO2ER activity at -0.92 V was enhanced whenusing anions with high CO2 affinity and high hydrophobicity,such as [NTF2](-). Among [NTF2](-)-based additives, [BMIM]-[NTF2] hada higher faradaic efficiency (FE) for formate (38.7%) compared toK-[NTF2] (23.2%) and Na-[NTF2] (18.5%) at -0.92V likely due to the presence of imidazolium cations that can furtherstabilize the intermediates on the surface and enhance CO2ER. Electrolytescontaining [DCA](-)-based additives with high hydrophilicityand low CO2 affinity had a very high HER selectivity (>90%FEH2) and low CO2ER selectivity regardless of the cationnature. This observation is attributed to the presence of hydrophilic[BMIM]-[DCA] in the vicinity of the catalyst, which impacts the microenvironmentaround the catalyst. We observed that [DCA](-) anionshave a high affinity to adsorb on Cu catalysts as soon as the catalystis submerged in the electrolyte. Although FTIR showed that [DCA](-) anions desorb from the surface at negative potentials,it is likely that [DCA](-) anions still remain inthe proximity of the electrode, next to the adsorbed cations, impactingthe transport of H2O and CO2, and altering theproduct selectivity. COMSOL calculations showed that the local pHis directly proportional to the H-2 evolution activity.Also, hydrophilic salts such as those with the [DCA](-) anion had a more alkaline local pH, which led to a lower CO2 concentration in the vicinity of the catalyst.

R&D on electrochemical approaches for chemical manufacturing is experiencing a renaissance, the direct result of society’s desire to reduce greenhouse gas emissions of the chemical industry, aiming to be carbon neutral by 2050. Two such processes have been performed for decades at scale: the chlor-alkali process that produces chlorine from aqueous sodium chloride, and the production of adiponitrile, an intermediate in the production nylon-6,6. Water electrolysis for hydrogen production is also being deployed now at scale. This report summarizes some of the many efforts to electrify chemical conversions, often using renewable feeds like water, CO2, and biomass-derived adducts, or waste-streams from other processes. Beyond efforts to reduce emissions, a very active research community also pursues a broad range of electro-organic conversions, some of which have major advantages over conventional reaction chemistries. Overarching challenges of implementing electrochemical manufacturing approaches are also discussed (e.g., limited familiarity with electrochemical processes in chemical engineering practice, insufficient availability of electrical power, and the variability of various renewable feeds).

The electrochemical transformation of sustainable feedstocks such as biomass derived species can help to electrify the chemical industry and reduce reliance on petroleum. Furfural (FF), one such biomass derived species, can be electrochemically reduced to form furfuryl alcohol (FA) and 2-methylfuran (MF) which are used to produce thermally stable molds and resins, and a fuel candidate or additive, respectively. Using Cu electrodes allows for selective production of FA or MF, dependent on the pH of solution, with MF requiring a low pH. The highly acidic conditions to produce MF also drive homogeneous side reactions and foul the Cu electrode with time. To better understand the nature of the build up on the electrodes, accelerated fouling conditions of high initial concentrations of FF and very low pH were investigated. At concentrations of 200 mM FF in 0.5 M H2SO4, we observed fouling of the Cu electrode during electrochemical hydrogenation and hydrogenolysis (ECH) of FF. The fouling of the electrode was also shown to be potential dependent, with poly(furfuryl alcohol) (pFA) forming at -560 mV RHE while an amorphous carbon resembling soot was observed more significantly at -700 mV RHE. The fouling of the Cu electrodes was shown to increase the polarization resistance during FF reduction, hindering the rates of reactions to FA and MF. Through control studies, it was found that the fouling is electrochemically-driven and requires the starting reactant FF to be present. By investigating and understanding the fouling of Cu electrodes during the electrochemical hydrogenation and hydrogenolysis of FF, catalysts can be better designed to inhibit fouling and be used for longer durations or for more cycles before requiring a treatment to regain activity or replacement. Additionally, while this work shows the detriment of carbon fouling on the electrode, pFA is a desirable product. Process intensification through development of a FF to pFA electrochemical step could be achieved through electroreduction with high concentration of FF in 0.5 M H2SO4. Electrode fouling can occur during furfural electroreduction to desired polymer intermediates and fuel additives in acidic electrolytes. The fouled material speciation is potential-dependent and can be mitigated by using lower concentrations of furfural.

Fine chemicals and fuels can be generated by electrochemical methods as an alternative to the currently in place thermocatalytic methods. The thermocatalytic methods require harsher reaction conditions, such as elevated pressures and temperatures, but also requires hydrogen gas as a reactant for reduction reactions which largely is produced by non-sustainable methods which emit high amounts of CO 2 . Electrochemical methods, in comparison, use in-situ generated protons in lieu of hydrogen gas which reduces the overall CO 2 generation. Electrifying the chemical industry will allow for the reduction in anthropogenic CO 2 generation by coupling a neutral or negative carbon emitting process with renewable electricity. Furfural (FF) is a biomass derived platform molecule produced at a scale above 300,000 metric tons annually and can used to produce furfuryl alcohol (FA) and 2-methylfuran (MF) through electrochemical hydrogenation and hydrogenolysis (ECH) respectively. FA is a fine chemical that is highly desirable for use in furanic molds, while MF has been identified as a fuel or fuel precursor. In this work, the kinetics of the FF ECH electrochemical system is decoupled and modeled to understand the conversion of FF. In this work, the electrochemical kinetics and non-electrochemical side reactions investigated in our previous works [1,2,3] are modeled to gain further insights into the mass balance and the longer-term phenomena associated with the FF ECH system. The FF ECH system is modeled as three contributing pieces: the ECH reactions, the non-electrochemical side reactions, and the evaporation of MF to the solvent trap for collection. The desired electrochemical reactions were investigated using a 2 compartment H-cell with a Cu flag electrode in the cathode compartment, and connected to a solvent trap held at -15°C. Experimentation was done in 0.1 and 0.5 M H 2 SO 4 with concentrations of FF between 10 and 120 mM FF. The catholyte had a cosolvent of 80:20 vol% water: acetonitrile and was purged with 60mL/min of nitrogen gas. To study the non-electrochemical reactions, vials of electrolyte with FF, FA, and MF in concentrations matching those found in electrochemical experiments were prepared and sample over time without the presence of any electrochemistry. The vial samples over time showed that mass loss occurred for the three furanics, however much more significantly for FA and MF, the two desired products. Lastly, the evaporation of MF from the catholyte to the solvent trap was studied by preparing the H-cell with a known concentration of MF and sampling over time. By modeling the FF ECH system this way, we were able to show the prominence of the competing side reactions and evaporation of MF to the solvent trap which provides insights into the mass balance and performance of the FF ECH system. We find that while the side reactions are more prevalent in the 0.5M H 2 SO 4 than the 0.1M H 2 SO 4 , that a higher MF yield is reached due to the evaporation and collection of MF in the solvent trap. A higher FA yield is found in the 0.1M H 2 SO 4 compared to the 0.5M H 2 SO 4 . [1] May, Andrew S., Steven M. Watt, and Elizabeth J. Biddinger. "Kinetics of furfural electrochemical hydrogenation and hydrogenolysis in acidic media on copper." Reaction Chemistry & Engineering 6, no. 11 (2021): 2075-2086 [2] Jung, Sungyup, and Elizabeth J. Biddinger. "Electrocatalytic hydrogenation and hydrogenolysis of furfural and the impact of homogeneous side reactions of furanic compounds in acidic electrolytes." ACS Sustainable Chemistry & Engineering 4, no. 12 (2016): 6500-6508 [3] Jung, Sungyup, and Elizabeth J. Biddinger. "Controlling competitive side reactions in the electrochemical upgrading of furfural to biofuel." Energy Technology 6, no. 7 (2018): 1370-1379

Electrochemical reduction of CO2 (CO2ER) is a promising technology to mitigate the CO2 level in the atmosphere, as well as, to produce value-added chemicals and fuels. Aqueous solutions are regarded as the most common electrolytes for CO2ER. However, there are some challenges such as low CO2 solubility and the presence of parasitic hydrogen evolution reaction which cause CO2ER in aqueous electrolytes to be inefficient in terms of selectivity and activity. A number of strategies have been proposed to enhance the efficiency for CO2ER in aqueous electrolytes. Among them, introducing additives to the aqueous solutions has attracted considerable attention. Depending on the chemical and physical properties of the additives, they have been demonstrated to improve the selectivity and activity in CO2ER. Herein, we provide a review on classification, mechanism, challenges, and perspectives of the additives in the aqueous electrolytes for CO2ER.

The understanding of electrochemical reactions for the hydrogenation and hydrogenolysis (ECH) of biomass derived species is important to design and adapt electrochemical reactors to generate desired chemicals sustainably at high yield. In this work, the ECH of furfural (FF) over Cu foil catalysts to furfuryl alcohol (FA) and 2-methylfuran (MF) was studied in a two-compartment semibatch reactor in acidic electrolytes (0.1 and 0.5 M H2SO4) with nitrogen sparging. We found that FA and MF underwent side reactions that follow first order kinetics with respect to the FA and MF concentrations in 0.1 M H(2)SO(4 )and 0.5 M H2SO4. MF evaporation from the catholyte in the presence of nitrogen sparging followed a first order dependence with the concentration of MF in the catholyte. Our previous work showed the ECH of FF over Cu followed noncompetitive Langmuir-Hinshelwood models. A kinetic model was developed to consider the electrochemical reactions, nonelectrochemical side reactions, and the evaporation of MF to investigate the competition between these three contributions to the mass balances. Insights were provided by using the model to consider two hypothetical cases where 1) evaporation of MF did not occur, and 2) side reactions did not occur, and a third realistic case where evaporation of MF and side reactions occurred. The model showed that without gas sparging promoting MF evaporation, 81.5% of products were undesirable at 98.5% FF conversion in 0.5 M H2SO4, and 30.6% of products were undesirable in 0.1 M H2SO4. N-2 sparging in the catholyte lowered the concentration of MF in the catholyte with a corresponding increase to the concentration in the solvent trap, where side reactions did not occur, allowing for increased MF yields. We showed that despite the faster side reactions to MF in 0.5 M H(2)SO(4 )compared to 0.1 M H2SO4, a higher yield to MF was reached in 0.5 M H(2)SO(4 )than in 0.1 M H(2)SO(4 )due to the beneficial impact of nitrogen sparging and the higher electrochemical production rate of MF.

CO2 electroreduction (CO2ER) has attracted considerable attention due to its promising results in producing valuable chemicals and fuels and mitigating global warming. Among different electrolytes, water-based solutions are the most common electrolytes for CO2ER due to their low cost, abundance, and eco-friendliness. However, the product selectivity and activity in aqueous electrolytes are poor due to their low CO2 solubility and the presence of the competing hydrogen evolution reaction (HER). Using ionic additives such as inorganic salts and ionic liquids can enhance CO2ER by controlling the water and CO2 concentration at the interface. Ionic additives can also impact the intermediate stability on the surface. In this study, the effect of additive anion and cation on CO2ER has been studied. A series of salts (10 mM) with different anions and cations were added to 0.1 M potassium bicarbonate (KHCO3). Bis(trifluoromethylsulfonyl)imide [NTF2]- or dicyanamide [DCA]- as anion were chosen due to their significantly different hydrophobicity and CO2 absorption capacity. Sodium (Na+), potassium (K+), 1-ethyl-3-methylimidazolium [EMIM]+, and 1-butyl-3-methylimidazolium [BMIM]+ were used as cation. Results showed that the effect of anion is more significant on CO2ER compared to cations. Adding DCA-based salts, regardless of the cation type significantly enhanced HER and suppressed CO2ER. According to the cyclic voltammetry in N2-saturated electrolytes with DCA anions, a current density ~44 mA/cm2 (regardless of the cation type) was observed at -1.12 V vs. RHE. By saturating the DCA electrolytes with CO2, the total current density decreased. Regarding the product selectivity, [DCA]-based salts also had a high faradaic efficiency (FE) for hydrogen and a very low FE for hydrocarbons even at high overpotentials. This can be justified by high hydrophilicity and strong adsorption of DCA-salts on the surface. The strong adsorption of DCA-salts was also confirmed by X-ray photoelectron spectroscopy (XPS) and In-situ electrochemical quartz crystal microbalance (EQCM). Strongly adsorbed DCA ions on the surface can promote hydrogen evolution reaction, destabilize the intermediates and suppress CO2ER. On the other hand, NTF2-based salts showed a lower HER activity compared to DCA-salts. Among different cations with NTF2 anion, Na[NTF2] showed a higher HER compared to [EMIM][NTF2] and [BMIM][NTF2]. According to the cyclic voltammetry in N2-saturated electrolytes with NTF2 anions, NaNTF2 showed a current density of ~14 mA/cm2 at -1.12 V vs. By saturating the NTF2 electrolytes with CO2, the total current density increased, in opposite to DCA-salts. This can show that NTF2 salts are able to enhance CO2ER. This can be due to their high hydrophobicity and CO2 absorption capacity. The best performance was observed for [BMIM][NTF2]. [BMIM][NTF2] showed a high faradaic efficiency (38.7%) for formate at -0.92 V vs. RHE. Electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance is more impacted by the anion nature. DCA salts showed a lower charge transfer resistance compared to NTF2 salts probably due to the enhanced HER which is kinetically faster than CO2ER. Moreover, an inductive loop was observed in EIS for both [EMIM][NTF2] and [BMIM][NTF2] additives (not for Na[NTF2]) which can be indicative of the interaction of CO2 with imidazolium cations at the interface which can facilitate formate formation.

Electrochemical processes offer sustainable means of production when coupled with renewable energy. While thermocatalytic processes require external hydrogen gas for reduction reactions, which generates copious amounts of CO2 in the generation of the hydrogen gas, electrochemical processes have the ability to use protons from the electrolyte in lieu of external hydrogen gas as a reactant. In addition to eliminating the hydrogen gas reactant, electrochemical processes can operate at room temperature and pressure. The development of electrochemical reactors for transformation of biomass derived species is of growing interest for the sustainable production routes it enables of various fine chemicals and fuels. Furfural (FF), one such biomass derived species can be electrochemically reduced to furfuryl alcohol (FA), a resin, and 2-methylfuran (MF), a potential fuel. To produce both FA and MF, acidic electrolytes and Cu catalysts can be used. While Cu electrodes allow for high selectivity to furfuryl alcohol or 2-methylfuran, the Cu electrodes suffer from stability issues caused by things such as fouling over longer durations of electrolysis. In this work, we intentionally operated FF ECH under conditions to promote fouling so that the impact of fouling could be investigated. This consisted of 200mM FF in the catholyte with pH 0 electrolyte in 20:80 acetonitrile:water. We used a Cu flag working electrode of 6cm2. We then recycled the Cu electrode for 3 runs of ECH at 3 hours, refreshing the catholyte after each run. A polymeric substance was observed on the Cu electrode surface after multiple uses which had identical IR spectroscopic features to poly(furfuryl alcohol). The impact of the polymeric coating was investigated further using electrochemical impedance spectroscopy, the chemical characterization was determined using x-ray photoelectron spectroscopy, and morphology was imaged using scanning electron microscopy.

bis(trifluoromethanesulfonyl)imide ([Pyr14][TFSI]) with organic solvent methyl propionate (MP) was investigated to gain a fundamental understanding of the thermal, physical and electrochemical properties. Estimation of the coulombic efficiencies on a copper electrode was additionally carried out using cyclic voltammetry as an initial screening to test the promise for lithium metal batteries. The addition of MP to [Pyr14][TFSI] suppressed the melting point, dramatically increased conductivity (from 0.56 mS/cm at 25 ??C in 0.8 m LiTFSI in [Pyr14][TFSI] to 11 mS/cm at 25 ??C in 0.8 m LiTFSI in a mixture of 1:7 mol ratio of [Pyr14][TFSI] to MP) and still maintained the electrochemical window (>5 V). While the addition of MP reduced the melting point and increased conductivity, the presence of cyclic carbonates in the cosolvent was necessary to enable deposition and stripping of lithium with high coulombic efficiencies. The fluorinated ethylene carbonate (FEC) appeared to enhance the SEI formation and suppress the Claisen reaction that MP enabled.