Electrochemical conversion of CO 2 requires selective catalysts and high solubility of CO 2 in the electrolyte to reduce the energy requirement and increase the current efficiency. In this study, the CO 2 reduction reaction (CO 2 RR) over Ag electrodes in acetonitrile-based electrolytes containing 0.1 M [EMIM][2-CNpyr] (1-ethyl-3-methylimidazolium 2-cyanopyrolide), a reactive ionic liquid (IL), is shown to selectively (>94%) convert CO 2 to CO with a stable current density (6 mA•cm −2 ) for at least 12 h. The linear sweep voltammetry experiments show the onset potential of CO 2 reduction in acetonitrile shifts positively by 240 mV when [EMIM][2-CNpyr] is added. This is attributed to the pre-activation of CO 2 through the carboxylate formation via the carbene intermediate of the [EMIM] + cation and the carbamate formation via binding to the nucleophilic [2-CNpyr] − anion. The analysis of the electrode−electrolyte interface by surface-enhanced Raman spectroscopy (SERS) confirms the catalytic role of the functionalized IL where the accumulation of the IL-CO 2 adduct between −1.7 and −2.3 V vs Ag/Ag + and the simultaneous CO formation are captured. This study reveals the electrode surface species and the role of the functionalized ions in lowering the energy requirement of CO 2 RR for the design of multifunctional electrolytes for the integrated capture and conversion.

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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.

This study is focused on the determination of the effects of processing time and temperature on the thickness, morphology, and hardness of boride layers grown on AISI 304L stainless steels. For boriding, a new molten salt electrolysis method called as CRTD-Bor (Cathodic Reduction and Thermal Diffusion-based boriding) was chosen due to its fast and green nature. CRTD-Bor of AISI 304L substrates was carried out in a borax-based molten electrolyte at temperatures ranging from 950 to 1050 °C for periods of 15 to 60 min at a constant current density of 200 mA/cm 2 . The x-ray diffraction analyses revealed the mixed iron boride phases including Fe 2 B, FeB. Moreover, cross-sectional scanning electron microscopy examinations confirmed the growth of these phases. Additionally, a phase homogenization (PH) step was adapted into CRTD-Bor to eliminate brittle FeB layer. It was founded that after 70 min of treatment at 1000 °C (15 min of CRTD-Bor + 55 min of PH) it is possible to grow % 40-lm-thick Fe 2 B layer exhibiting 1700 ± 100 HV on the surface with excellent adhesion to the substrate (HF1). Besides, kinetic calculations showed the activation energy (Q) of boride layer growth as 181.45 kJ/mol.