Moderate Polarity Research Articles

Separation performance of p-nitro-octadecyloxy-calix[8]arene as stationary phases for capillary gas chromatography

Here we report the first example of employing p-nitro-octadecyloxy-calix[8]arene (C8A-NO2) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated C8A-NO2 column provided column efficiencies of 2554 plates/m and showed moderate polarity. Its selectivity and retention behaviour were investigated by a number of mixtures of diverse analytes and their isomers. It was found that the C8A-NO2 column exhibited high resolving capability for aliphatic and aromatic analytes from apolar to polar nature, especially for positional and structural isomers. Among them, advantageous resolving capability over the commercial polysiloxane DB-1701 and DB-17 columns was obtained for chloroaniline and bromoaniline isomers. In addition, the C8A-NO2 column was applied for the determination of isomer impurities in commercial reagents of geraniol, cis-decahydronaphthalene, and trans-decahydronaphthalene.

Solvent Dependence of Cationic-Exciplex Emission: Limitation of Solvent Polarity Functions and the Role of Hydrogen Bonding.

Conventional exciplexes are products of excited-state charge generation reactions between neutral reactants (e.g., A* + D → A•-D•+), whereas cationic exciplexes are products of charge shift reactions of cations with neutral donors (e.g., A+* + D → A•D•+). Compared herein is the solvent-dependent fluorescence of a cationic exciplex with extant data for conventional exciplexes. Although linear correlations of conventional exciplex emission maxima with the Lippert-Mataga solvent polarity function are well documented in low to moderate polarity solvents, the correlations are often poor in more polar solvents. A number of such plots in moderate to high polarity solvents show a strong curvature. Intriguingly, for these same cases, plots of emission maxima versus the solvent dielectric constant (ε) are remarkably linear. Interestingly, emission maxima for the cationic exciplex of 1+ in nitrile and alcohol solvents also correlate linearly with ε. The solvent dependency for cationic exciplex emission maxima on ε is ca 1/3 of that for conventional exciplexes, which is ascribed to solvent stabilization of both the excited state and the ground state for cationic exciplexes. Differences in exciplex emissions between nitrile and alcohol solvents for 1+ are attributed to hydrogen bonding, with larger differences in higher hydrogen-bond acidity solvents.

Glass-Forming Ability and Soft Magnetic Properties of (Co75Ti25)100-xFex (x; 0-20 at.%) Systems Fabricated by SPS of Mechanically Alloyed Nanopowders.

Due to their outstanding mechanical properties and soft magnetic characteristics, cobalt-based metallic glassy alloys have stimulated much interesting research. These metastable ferromagnetic materials possess very small magnetocrystalline anisotropy, and almost zero magnetostriction. They reveal low coercivity, extremely low core loss, moderate saturation polarization, and very high magnetism. Despite these attractive physical behaviors, Co-based metallic glasses are difficult to obtain by the melting/casting and conventional rapid solidification techniques due to their poor glass-forming ability. In the present study, we succeed in preparing (Co75Ti25)100−xFex (x; 0–20 at.%) metallic glassy powders, using a mechanical alloying approach. The end product of the as-prepared powders was consolidated into full dense cylinders with large-diameter and thickness (2 × 2 cm), using spark plasma sintering technique. The results have shown that the consolidation step did not lead to any undesired crystallizations or phase transformations, and the as-consolidated buttons maintained their unique short-range order structure. These bulk metallic glassy systems possessed high glass-transition and crystallization temperatures, suggesting their high thermal stability. However, they showed low values of the reduced glass-transition temperatures, indicating that this system is difficult to prepare by the conventional way of preparations.

Triptycene-based dicationic guanidinium ionic liquid: A novel stationary phase of high selectivity towards a wide range of positional and structural isomers

This work presents a new triptycene-based dicationic guanidinium ionic liquid (TPG) as the stationary phase for gas chromatography (GC). To our knowledge, this is the first example of employing a dicationic guanidinium ionic liquid (GIL) for chromatographic analyses. As a result, the TPG column exhibited moderate polarity and column efficiency of 3840 plates/m and 3120 plates/m measured by naphthalene and 1-octanol at 120 °C, respectively. Particularly, the TPG column exhibited distinctly advantageous performance for the challenging Grob test mixture and the isomer mixture of phenols and anilines over the monocationic GIL and its counterpart with dicationic immidazolium units (TP-2IL). Also, it showed higher selectivity towards the isomers of alkanes, alcohols, diethylbenzenes, bromotoluenes, bromonitrobenzenes than the commercial DB-35MS column. Moreover, the TPG column achieved improved thermal stability over the GIL column and excellent repeatability with the RSD values of 0.01–0.05% for run-to-run, 0.11–0.24% for day-to-day and 2.4–4.1% for column-to-column. Its application to GC–MS analysis of the essential oil of Mentha haplocalyx proved its good potential for analysis of complex samples.

A novel method for the synthesis of biodiesel as an eco-friendly and sustainable fuel

Biodiesel is a green diesel fuel that is synthesized via the transesterification reaction of plant oils or animal fats with light alcohols, mainly methanol, in the presence of commonly homogeneous alkaline catalysts. One way to make the biodiesel synthesis process more eco-friendly is the use of heterogeneous catalysts as they are reusable. But with these catalysts, the transesterification reaction mixture will be a three-phase mixture containing methanol, oil and catalyst that leads to long reaction times and high process costs. In this study, the ultrasound waves were used to synthesis of the biodiesel from the Jatropha oil in the presence of CaO as a heterogeneous catalyst. The effect of two different co-solvents (acetone & hexane) on improving the homogeneity of the reaction mixture and therefore to enhance the conversion yield of the oil to biodiesel was considered. Experiments were carried out by a probe type ultrasonic instrument at an output power of 200 W and frequency of 20 kHz. The results showed that both of the considered co-solvents had positive effect on developing the conversion yield and the acetone was the more efficient one due to its moderate polarity, which could improve the miscibility of the oil with the methanol. A biodiesel sample with a conversion yield of 90.33% was synthesized under optimal operating conditions including 25% v/v acetone to methanol, 12:1 methanol to oil molar ratio, 4% w/w catalyst to oil, 55°C reaction temperature and 60 min reaction time. Hnmr and densitometry were used to determine the percentage of the synthesized biodiesel samples. Also, some of the physicochemical properties of the synthesized biodiesel were analyzed, which were in accordance with the ASTM and EN standards.

Combined Effects from Solvation and Nuclear Quantum Fluctuations on Autoionization Mechanisms in Aqueous Clusters.

Using path-integral molecular dynamics simulations, we examine isomerization paths involving collective proton transfers in [H2O]5 and [H2O]8 clusters under cryogenic conditions. We focused attention on combined effects derived from solvation and nuclear quantum fluctuations on the characteristics of free energy barriers and relative stabilities of reactants and products. In particular, we analyzed two different processes: the first one involves the exchange of donor-acceptor hydrogen bond roles along cyclic moieties, whereas the second one corresponds to charge separation leading to stable [H3O]+[OH]- ion pairs. In the first case, the explicit incorporation of quantum tunneling introduces important modifications in the classical free energy profile. The resulting quantum profile presents two main contributions, one corresponding to compressions of O-O distances and a second one ascribed to nuclear tunneling of the light protons. Solvation effects promote a moderate polarization of the cyclic structures and a partial loss of concertedness in the collective modes, most notably, at the onset of tunneling. Still, the latter effects are also sufficiently strong to promote the stabilization of ion pairs along the classical trajectories. In contrast, the explicit incorporation of nuclear quantum fluctuations leads to charge separated configurations that are marginally stable. As such, the latter states could also be regarded as short-lived intermediate states along the reactive exchange path.

Polyphenolics and Antioxidant Activity of Mahonia jaunsarensis Ahrendt: A Narrow Endemic to West Himalaya

Mahonia jaunsarensis (Family Berberidaceae) is an endemic species of the Himalaya narrowly distributed in Chakrata hills of Uttarakhand. Considering that the species is traditionally used by local inhabitants for various purposes, this study was made to explore its biochemical attributes using diverse solvent systems, i.e., ethanol, methanol and distilled water. Results revealed a varied range of total phenolics (1.00–1.39 mg GAE/g); tannins (1.01–1.11 mg TAE/g); flavonoids (1.07–1.22 mg QE/g); and flavonols (0.71–1.04 mg QE/g) across solvent extractions. Likewise, in vitro antioxidant activity (i.e., ABTS 0.82–1.09; DPPH 0.94–1.16; and FRAP 0.81–1.05 mM AAE/100 g fresh weight) varied. Results are indicative that the species possess higher bioactive attributes and a good source of natural antioxidant. A solvent system with moderate polarity, such as methanol, was found best for harnessing the maximum potential. The study provides baseline information on biochemical attributes of the species, which can, with due R&D interventions, be extended for the industrial applications.

Determination of Phthalate and Metabolites in Human Urine by Lithium Bis(trifluoromethanesulfonyl)imide-Enhanced Dual Microextraction Method Optimized by Central Composite Design

The traditional optimization of extraction for sample pre-treatment usually involves only the single-factor experimental design to obtain the best conditions of performance. However, in optimization, only employing the single-factor experimental design becomes less frequent as it ignores the interaction among various factors. To identify the effective or critical factors and interactions among them in a sample pre-treatment, the experimental design should be conducted by the design of experiments (DoE). In this study, lithium bis(trifluoromethanesulfonyl)imide (LiNTf2)-enhanced dual microextraction method, a new type of ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) was applied for the simultaneous enrichment and extraction of phthalate (PAE) and metabolites showing weak to moderate polarity in human urine. The conditions were optimized by the single-factor experimental design, full factorial design, and central composite design (CCD) based on DoE methodologies. Under optimal conditions, the proposed method performed high recoveries (95.19–98.3%) and low LODs (0.14–0.46 μg L−1) in the range of 2–500 μg L−1 for six PAE and metabolites in human urine. Extending from this study, this method has excellent potential for the enrichment and extraction of chemical compounds ranging from weak to moderate polarity in environmental and biological matrices as well. Besides, for the optimization of sample pre-treatment, DoE is necessary and vital in analytical chemistry and clinical laboratories to obtain the interactions between various factors instead of using only a single-factor experiment.

Многокомпонентные неводные электролиты для работы суперконденсаторов при повышенных температурах

Multicomponent non-aqueous electrolytes based on cyclic carbonates and tetraethylammonium tetrafluoroborate have been developed for the operation of supercapacitors at elevated temperatures. Propylene carbonate, which has a high dielectric constant and a high boiling point, was used as the main solvent of electrolytes. However, a significant drawback of propylene carbonate is its high viscosity, which leads to decrease in the electrical conductivity of electrolytes based on it compared to electrolytes based on acetonitrile. To increase the electrical conductivity, an additional component was introduced into the electrolyte – a cosolvent with the necessary set of properties. When choosing cosolvents, two approaches were used. In the first case, to increase the dielectric permittivity of the liquid phase, ethylene carbonate having a higher dielectric constant than propylene carbonate was introduced into the electrolyte. This approach made it possible to significantly increase the electrical conductivity of the electrolyte and to achieve high resource stability of the supercapacitor. The values of the specific capacitance and energy of the supercapacitor with the introduction of ethylene carbonate in the electrolyte practically did not change. In the second case, butyl acetate, which has a low viscosity but has a moderate polarity and a sufficiently high boiling point, was used as a co-solvent. In this case, not only an increase in the electrical conductivity of the electrolyte was observed, but also a significant increase in the capacitive characteristics of the supercapacitor. It is shown that the use of a mixture of cyclic carbonates and esters as a solvent in the composition of the electrolyte can increase its specific conductivity by 40%, and the specific energy consumption of a supercapacitor by 20%. The developed electrolytes provide long-term operation of supercapacitors both at room temperature and at elevated temperatures up to 80 °С.

Mediating the confliction of polarizability and breakdown electric-field strength in BNST relaxor ferroelectric for energy storage applications

For relaxor ferroelectric energy-storage capacitors, the breakdown electric-field strength was usually enhanced by sacrificing polarization intensity. In this work, the relaxor ferroelectric Bi0.41Na0.35Sr0.21TiO3 (BNST) has been chosen with the aim to achieve excellent energy storage properties via grain size engineering. By tailoring the grain sizes of BNST relaxor ferroelectric, the fraction of rhombohedral phase was increased, and a medium ferroelectric polarization and high breakdown strength was obtained. The enhancement of energy-storage properties with large recoverable energy density (Wrec = 2.04 J/cm3) and high energy efficiency (ƞ = 82.4%) was simultaneously achieved under a low electric-field (E = 135 kV/cm) with the grain size of 1.04 μm. In addition, the BNST ceramics exhibited good fatigue properties with the variation of Wrec less than 1% over 106 cycles. The grain size engineering greatly increases dielectric breakdown strength because of the denser microstructure and moderate polarization intensity, indicating that it is an effective approach to improve the energy-storage performance in relaxor ferroelectrics.

Two chiral types of randomly rotated ommatidia are distributed across the retina of the flathead oak borer Coraebus undatus (Coleoptera: Buprestidae).

Jewel beetles are colorful insects, which use vision to recognize their conspecifics and can be lured with colored traps. We investigated the retina and coloration of one member of this family, the flathead oak borer Coraebus undatus using microscopy, spectrometry, polarimetry, electroretinography and intracellular recordings of photoreceptor cell responses. The compound eyes are built of a highly unusual mosaic of mirror-symmetric or chiral ommatidia that are randomly rotated along the body axes. Each ommatidium has eight photoreceptors, two of them having rhabdomeres in tiers. The eyes contain six spectral classes of photoreceptors, peaking in the UV, blue, green and red. Most photoreceptors have moderate polarization sensitivity with randomly distributed angular maxima. The beetles have the necessary retinal substrate for complex color vision, required to recognize conspecifics and suitable for a targeted design of color traps. However, the jewel beetle array of freely rotated ommatidia is very different from the ordered mosaic in insects that have object-directed polarization vision. We propose that ommatidial rotation enables the cancelling out of polarization signals, thus allowing stable color vision, similar to the rhabdomeric twist in the eyes of flies and honeybees.

High-resolution performance of triptycene functionalized with polycaprolactones for gas chromatography

Developing highly selective stationary phases is essential to address the issues for separation of analytes with similar properties and various components in complex samples. Herein, we report a new triptycene-based material functionalized with polycaprolactone moieties (TP-PCL) as the stationary phase with high-resolution performance for gas chromatography (GC). The TP-PCL capillary column exhibited column efficiency of 5555 plates/m and moderate polarity. On the column, dozens of mixtures of positional and structural isomers can be well resolved, involving benzene derivatives with varying substituents (alkyl, halo, nitro, hydroxyl, amino), naphthalene derivatives, alkanes and alcohols. It exhibits advantageous performance for high resolution of the critical pairs of alkylbenzenes, phenols, anilines and alkanes over the PCL column and commercial DB-35 MS column with similar polarity. Moreover, the TP-PCL column showed excellent separation repeatability and reproducibility with RSD values of 0.02%−0.07% for run-to-run (n = 4), 0.11%−0.18% for day-to-day (n = 4) and 2.1%−4.7% for column-to-column (n = 4). In addition, it exhibited distinctly enhanced thermal stability in contrast to the PCL column. Its application to analysis of the essential oil from Artemisiae argyi proves its good potential for practical use.

Adenine-functionalized polypropylene glycol: A novel stationary phase for gas chromatography offering good inertness for acids and bases combined with a unique selectivity

This work presents the investigation of utilizing adenine-functionalized polypropylene glycol (APPG) for capillary gas chromatographic separations. The statically coated APPG column (0.25 mm i.d.) showed moderate polarity and high column efficiencies of 4660 plates/m and 4376 plates/m determined by n-octanol and naphthalene, respectively. Remarkably, the APPG column baseline resolved all the components of the Grob test mixture and displayed good peak shapes for some stringent analytes that are prone to peak tailing or severe adsorption. Also, it achieved complete separation of dimethylaniline isomers, which are difficult to be resolved due to their high resemblance in structures and properties. The above results demonstrate the high selectivity and inertness of the APPG column and its distinct advantages over the polypropylene glycol (PPG) column and commercial polyethylene glycol (PEG) column. In addition, its separation performance has good repeatability with the RSD values on retention times below 0.05% for run-to-run, 0.11–0.12% for day-to-day and 1.7–1.9% for column-to-column, respectively. Further, the APPG column was applied to determination of isomer impurities in commercial dimethylaniline products and to determination of the additives of anilines and phenols in a hair-dye product, proving its great potential for practical GC analysis.

π-Extended Four-Coordinate Organoboron N,C-Chelates as Two-Photon Absorbing Chromophores.

Four-coordinate N,C-chelate organoboron dyes with alkynyl spacers were synthesized by Heck alkynylation. These dyes are π-extended analogues of the recently reported class of four-coordinate borylated arylisoquinolines (BAI). Depending on the electron-donor substitution, they feature an intramolecular charge-transfer (ICT) character in the excited state. This translates into pronounced apparent Stokes shifts (up to 8500 cm-1) and a solvatofluorochromic behavior. In general, the observed emission quantum yields are high in nonpolar media (ΦF ca. 0.5-0.6). For the dye with the most pronounced ICT rather high emission quantum yields (ΦF ca. 0.4) are observed for emissions with maxima longer than 600 nm in solvents of moderate polarity. The π-extended dyes show interesting two-photon absorption (TPA) properties, maintaining high cross sections (up to 60 GM) in the near-infrared wavelength window (>900 nm). One of the dyes was designed as dimeric chromophore, integrating the acceptor-π-acceptor (A-π-A) format. This alternative design showed no ICT behavior but led to the observation of high two-photon-absorption (TPA) cross sections (ca. 220 GM at 700 nm). All investigated dyes show pronounced photostability, providing added value to this structural and photofunctional extension of the BAI dye platform.

Bonded by Interactions: Polarising Factors and Integrative Capacities of the News Media in Hungary

The article addresses the issue of political polarisation in the news media in Hungary. Hungary is an illustrative case of a country which has been studied as the example of high political parallelism in news media, and one of the most politically polarised societies in Europe. We contribute to the literature in a number of ways. First, to our knowledge, this is a pioneering study in the application of network analysis to measuring political polarisation in the news media. Second, we provide evidence that fragmentation and heavy partisanship do not necessarily lead to extreme polarisation. The study presents an issue-centred and context-based approach to assessing whether mass communication channels form integrated or divided news media spaces for public discussion. For an empirical test, we explore the news media networks of three of the most widely covered issues of 2014. To link a medium to another one, we concentrate on interactions, which are defined as explicit citations or hyperlinks to the content of other media products and the communication of politicians. The findings support the claim of moderate polarisation in the Hungarian news media. Although ideologically divergent blocs are detected, there are intensive interactions between news media outlets of different political colours.

Lipids Extraction from Wet and Unbroken Microalgae <i>Chlorella vulgaris </i>Using Subcritical Water

Lipids extraction from wet and unbroken microalgae (Chlorella vulgaris) using subcritical water with aid of co-solvents has been investigated. Lipids extraction from wet and unbroken microalgae has a crucial role in order to eliminate dewatering and drying steps. Subcritical water is able to extract lipids from feedstock with high water content. This work was conducted to study several factors affecting in subcritical water extraction (SWE) from wet and unbroken microalgae. In this study, effect of co-solvent types (without co-solvent, chloroform, methanol, ethanol, ethyl acetate, and n-hexane) under subcritical water (microalgae = 5g (dry weight), moisture content= 94.12%, T= 160°C, P = 80 bar, t= 30 min), extraction time (15 min, 30 min, 1 h, 3 h, and 5 h), and temperature (160o C, 180o C and 200o C) on yield of lipids were investigated orderly. Yield of lipids obtained without co-solvent (water polarity index = 10.2) and with co-solvents of methanol (PI=5.1), ethanol (PI=5.2), chloroform (PI=4.1), ethyl acetate (PI=4.4), and n-hexane (PI=0.1) were 38.73%, 26.47%, 26.12%, 51.93%, 53.40%, and 25.59%, respectively compared to the yield of lipids extracted using Bligh and Dyer method. Ethyl acetate is solvent with moderate PI, therefore can extract more lipids that is also have moderate polarity. Ethyl acetate shows a good performance to extract lipids from wet and unbroken microalgae because ethyl acetate can extract broader range of lipids including neutral and polar lipids. This study also found that increasing of extraction time and temperature to extract lipids in subcritical water condition can increase yield of lipids.

Photochemical Protection of Reactive Sites on Defective TiO2- x Surface for Electrochemical Water Treatment.

The electrode is the key in electrochemical process for water and wastewater treatment. Many nonstoichiometric metal oxides are active electrode materials but have poor stability under strong anodic polarization due to their susceptible nature of the oxygen vacancies on surface and subsurface as defective reactive sites. In this work, a novel photochemical protecting strategy is proposed to stabilize the defective reactive sites on the TiO2- x surface and subsurface for long-term anodic oxidation of pollutants. With this strategy, a novel photoassisted electrochemical system at low anodic bias is further constructed. Such a system exhibits a high protecting capacity at a low operation cost for electrochemical degradation of bisphenol A (BPA), a typical persistent organic pollutant. Its excellent photochemical protecting capacity is found to be mainly attributed to the mild non-band-gap excitation pathways on the defective TiO2- x electrode under both visible-light irradiation and moderate anodic polarization. Under real sunlight irradiation, a 20 run cyclic test for BPA degradation demonstrates the excellent performance and stability of the constructed system at low bias without significant oxygen evolution. Our work provides a new opportunity to utilize the defective and reactive TiO2- x for efficient, stable, and cost-effective electrochemical water treatment with the aid of its photo- and electrochemical bifunctional properties.

Mountain-like nanostructured 3D Ni3S2 on Ni foam for rechargeable aluminum battery and its theoretical analysis on charge/discharge mechanism

Transition metal sulfides are expected to be excellent candidates for aluminum batteries owing to their moderate polarity. Herein, Ni3S2/Ni cathode materials with unique morphology and good electrochemical performance has been successfully synthesized for aluminum battery by an effective chemical synthesis method. The galvanostatic charge/discharge measurement of the battery shows the initial discharge specific capacity of 236 mAh g−1 at a current density of 10 mA g−1, and it retains a reversible capacity of over 40 mAh g−1 after 200 cycles, indicating a good capacity retention of the prepared electrode. More importantly, a two-step insertion mechanism of Al3+ in the Ni3S2/Ni cathode is put forward based on the experimental measurements and theoretical simulations. By calculation of the formation energy for Alx(Ni3S2)24, the single-tunnel insertion of Al3+ into the interstitial sites of Ni3S2 at the higher discharge plateau and multi-tunnel at the lower one are deduced. This work not only provides an effective method, but also theoretical guidelines for the design and synthesis of promising cathode materials.

3D Patterning of Si by Contact Etching With Nanoporous Metals.

Nanoporous gold and platinum electrodes are used to pattern n-type silicon by contact etching at the macroscopic scale. This type of electrode has the advantage of forming nanocontacts between silicon, the metal and the electrolyte as in classical metal assisted chemical etching while ensuring electrolyte transport to and from the interface through the electrode. Nanoporous gold electrodes with two types of nanostructures, fine and coarse (average ligament widths of ~30 and 100 nm, respectively) have been elaborated and tested. Patterns consisting in networks of square-based pyramids (10 × 10 μm2 base × 7 μm height) and U-shaped lines (2, 5, and 10 μm width × 10 μm height × 4 μm interspacing) are imprinted by both electrochemical and chemical (HF-H2O2) contact etching. A complete pattern transfer of pyramids is achieved with coarse nanoporous gold in both contact etching modes, at a rate of ~0.35 μm min−1. Under the same etching conditions, U-shaped line were only partially imprinted. The surface state after imprinting presents various defects such as craters, pores or porous silicon. Small walls are sometimes obtained due to imprinting of the details of the coarse gold nanostructure. We establish that np-Au electrodes can be turned into “np-Pt” electrodes by simply sputtering a thin platinum layer (5 nm) on the etching (catalytic) side of the electrode. Imprinting with np Au/Pt slightly improves the pattern transfer resolution. 2D numerical simulations of the valence band modulation at the Au/Si/electrolyte interfaces are carried out to explain the localized aspect of contact etching of n-type silicon with gold and platinum and the different surface state obtained after patterning. They show that n-type silicon in contact with gold or platinum is in inversion regime, with holes under the metal (within 3 nm). Etching under moderate anodic polarization corresponds to a quasi 2D hole transfer over a few nanometers in the inversion layer between adjacent metal and electrolyte contacts and is therefore very localized around metal contacts.

Investigation of the cathode polarization and carbon deposition in a molten carbonate direct carbon fuel cell

Molten carbonate direct carbon fuel cells (MC-DCFCs) are among the most promising devices for high-efficiency energy conversion and clean power generation from coal. Many studies have focused on the anode performance, while little attention was paid to the cathode. In the present study, we comprehensively investigate the cathode polarization performance, revealing the reactions taken place and the impact of several important operation parameters on reaction rate. The results show that the reduction of inputted gases is the primary reaction at moderate cathodic polarization of a gold electrode, which could benefit from incorporation of an optimal O2/CO2 molar ratio of 1/2, increase of the gas flux or reaction temperature to a certain extent. Interestingly, with a sufficient overpotential applied, an unexpected carbon deposition phenomenon on the cathode is observed. To give an insight into this reaction, several material characterization techniques and electrochemical tests are conducted to analyze the composition and formation conditions of the deposit, respectively. It shows that the carbon deposition is resulted from the reduction of carbonate ions in the electrolyte, which occurs when the cathode potential reaches a critical value of −1.5 V, corresponding to a current density of −32 mA cm−2. To avoid the contamination of the cathode surface by the carbon deposition when operating an MC-DCFC, a feasible strategy is using a sufficiently large cathode to keep the cathodic current density as well as overpotential below the critical value.