Sulfate-based Electrolytes Research Articles

Exploring electrochemical mechanisms for clindamycin degradation targeted at the efficient treatment of contaminated water

Numerous studies reveal pollutants like clindamycin (CLD) in the environment, posing environmental and health risks. Conventional water treatment methods are ineffective at removing these contaminants, typically found in low concentrations. An innovative treatment approach is introduced through pre-concentration via adsorption, which is highly efficient, energy-saving, and reusable. The innovation uses solvents like methanol or ethanol to desorb pollutants, creating concentrated CLD solutions for more effective electrochemical degradation than conventional methods. Thus, this study explores, for the first time, the behavior of CLD electro-oxidation in different media—water, methanol, and ethanol—using a Dimensionally Stable Anode (DSA®-Cl₂). The study reveals distinct degradation mechanisms and offers new insights into solvent-assisted electrochemical treatments. After 30 min of electrolysis, all the current densities evaluated promoted significant degradation, ranging from 90 to 92%. The energy consumption was 2.9 Wh m⁻³ per percentage point at current densities of 2 and 3.5 mA cm⁻2. This demonstrates that using higher current densities over shorter electrolysis times is feasible, achieving removal rates of approximately 90%.The performance of chloride-based electrolytes was superior to that of sulfate-based electrolytes due to the ability of DSA®-Cl2 electrodes to generate reactive chlorine species more efficiently. A higher concentration of supporting electrolytes initially improved CLD removal, but no significant changes were observed after 1 h. Neutral pH conditions optimized CLD degradation, achieving up to 91% removal. Higher pollutant concentrations were associated with lower kinetic constants and decreased removal percentages. Methanol and ethanol enhanced removal rates to 98.3% and 92.3%, respectively, by generating oxidizing species such as methoxy, hydroxymethyl, and ethoxy radicals. The degradation by-products differed across the three media, with each solvent exhibiting distinct oxidation mechanisms. These findings highlight the potential of using methanol or ethanol as an electrolytic medium with efficiency comparable to water.

Electrochemical deposition of cobalt phosphorus for hard magnetic micro devices and the impact on magnetic anisotropy

When fabricating magnetic components for micro-electro-mechanical systems, the intrinsic material properties as well as the magnetic anisotropy of the deposited material and the fabricated devices must be adjusted to the application. This work focuses on electrochemically deposited cobalt phosphorus layers from a sulfate-based electrolyte to be used as hard magnetic scales in position measurement systems. In preliminary tests round discs (5 mm diameter, 20 or 10 μm height) were fabricated, showing the influence of three process parameters (current density, pH-value and temperature) on the chemical composition and the magnetic behavior of the deposited cobalt phosphorus. Hereby deposition parameters to produce hard magnetic cobalt phosphorus are defined. Deposits with up to 6 wt.-% phosphorus show hard magnetic behavior, whereas deposits with more than 6 wt.-% show soft magnetic behavior. This is correlated with a transition from crystalline to amorphous structures. In further investigations arrays of micro scales (40 μm width, 10 μm height) were fabricated to show the influence of direct current and pulsed current on the properties of the deposits. Pulsed current increases coercive field strength by about 40 %, resulting in maximum values of 23 kA/m (in-plane) and 14 kA/m (out-of-plane). Remanence increases by about 30 %, resulting in maximum values of 0.40 T (in-plane) and 0.2 T (out-of-plane). Pulse plating changes preferred orientation from (110) to (100) and slightly increases grain size by about 20 %, resulting in an average grain size of 25 nm.

Formation and conversion of hydrate zinc sulfate hydroxide in aqueous Zn/MnO2 batteries

Aqueous Zn/MnO2 batteries (AZMBs) are suitable for large-scale energy storage because of the advantages of safety, low cost and environmentally friendliness. However, the energy storage mechanism in AZMBs is still inconclusive, especially in sulfate-based electrolytes. In this work, we investigate the formation and conversion mechanisms of hydrate zinc sulfate hydroxide, Zn4SO4·(OH)6·xH2O (ZSH), aiming to elucidate the reaction mechanism and capacity origin of AZMBs with ZnSO4 and MnSO4 as the electrolyte. Results show that ZSH is an important intermediate in the electrolyte. It is observed that the electrochemical reaction occurs at the cathode/electrolyte interface involving the generation of ZSH-induced ZnMn3O7‧2H2O during a long-term cycling. In addition, transformation of ZSH to Zn at the anode/electrolyte interface is observed, implying that ZSH not only induces the uneven deposition of Zn2+ from electrolyte, but also in-situ converts into metallic Zn during the repeated cycling. This research provides an in-depth understanding of the formation and conversion of ZSH in AZMBs with potential impacts on Zn anode protection.

Regulated Interfacial Proton and Water Activity Enhances Mn2+/MnO2 Platform Voltage and Energy Efficiency

Aqueous zinc battery (AZB) is one of the most promising energy storage systems for large-scale applications due to its high safety, low cost, and environmental friendliness. To match the high capacity of zinc metal (~820 mAh g-1), various cathode materials, such as oxides, open structure analogues, chalcogens, and halogens, have been explored for AZBs. Among them, manganese dioxide (MnO2) has been considered to be one of the most attractive candidates due to its high capacity (~308 mAh g-1 for one-electron transfer) and adequate redox potential (~0.70 V vs. SHE). Recently, the MnO2 dissolution/deposition charge storage mechanism has been demonstrated to further increase the voltage and capacity of Mn-based AZBs. The dissolution/deposition (Mn2+/MnO2) is a two-electron transfer process, which doubles the theoretical capacity of MnO2 cathode to ~616 mAh g-1 and considerably increases the redox potential (~1.229 V vs. SHE). The charge storage via the dissolution/deposition mechanism pushes the aqueous-based energy density even higher, to over 1000 Wh kg-1.However, this charge storage mechanism involves liquid-solid transition, as well as the thermodynamics and kinetics of this reaction are highly dependent on the acidity and interfacial environment. Yet, the opposite effect of interfacial H+ on the dissolution/deposition processes and the role of interfacial H2O are rarely discussed. Here we introduce tetrafluoroborate anion (BF4 -) into the sulfate-based electrolyte to regulate the interfacial H+ and H2O activity. First, BF4 - hydrolysis increases the electrolyte’s acidity, promoting MnO2 dissolution. Second, BF4 - forms an H-bond network with interfacial H2O that assists H+ diffusion while retaining sufficient H2O supply to facilitate MnO2 deposition. As a result, the cathode-free Zn//MnO2 electrolytic cell achieves a high plateau of ~1.92 V and energy efficiency of ~84.23 % in the BF4 - containing electrolyte. Significantly, the cell delivers 1000 cycles at 1 C with ~100 % Coulombic efficiency and a high energy efficiency retention of 93.65 %. Our findings disclose a new strategy to promote Mn2+/MnO2 platform voltage and energy efficiency for future large-scale energy storage systems.

Deposition and removal of manganese oxide in zinc electrowinning

Zinc electrowinning in sulfate-based electrolytes produces zinc at the cathode and oxygen gas at the anode. Lead anodes are commonly used despite its low activity towards oxygen evolution and potential environmental hazards. Recent advances in materials for oxygen evolution in acidic electrolytes offers a wide variety of alternative anode catalysts with much higher performance than lead. However, significant formation of manganese oxide alongside oxygen evolution at the anode prevents introduction of new and more active catalytic coatings. In this work, we investigate manganese oxide deposition at IrO2Ta2O5 coated Ti electrodes using chronoamperometry, linear sweep voltammetry and rotating disc electrode. The morphologies of the electrode and deposited manganese oxide are also examined. Oxygen evolution is observed to primarily occur at the electrode and not on the growing manganese oxide deposit. We provide experimental evidence that deposition of manganese oxide gradually becomes limited by diffusion of Mn2＋ within the growing manganese oxide deposit itself. We interpret this to be due to formation of a poorly conducting outer part of the deposit. An electrochemical sequence for removal of deposited manganese oxide is developed and validated in synthetic electrolyte (2molL-1 H2SO4 + 0.15molL-1 Mn2+) and industrial electrolyte. Most importantly the sequence includes formation of a prelayer of manganese oxide at a low electrode potential (1000s at 1.45V or 7Am−2) as we show this to reduce more easily. Furthermore, a short reduction step (100s at 0.4V or −35Am−2) is then sufficient to diminish the adhesion of remaining manganese oxide and allow for easy mechanical removal. Implementing this method can make it possible to replace the currently used anodes in zinc electrowinning with more energy efficient and environmentally friendly anodes.

Localized Electrochemical Deposition Using Copper Pyrophosphate-Based Electrolyte

Additive manufacturing (AM) has gained popularity across various industries due to its cost-effectiveness, low material consumption, and minimal environmental impact. Localized electrochemical deposition (LECD), as one of the AM methods, has the capability to produce microcomponents or structures at an microscale in a specific position as designed, without the need for any mask or support material[1]. By reducing copper ions in the local area according to the position of the micro-wire, 3D structures could be produced. This electrochemical deposition process has a significant advantage in that it is a low-temperature process and has lower costs compared to other processes[2].Using the LECD process, the micrometer of copper columns was conventionally deposited in copper sulfate-based electrolyte[3]. However, this electrolyte has the possibility to cause damage to the metal substrate used as the cathode due to its low pH, resulting in metal dissolution. The utilization of copper pyrophosphate-based electrolyte, which is a solution with a pH close to neutral, can solve this problem. Also, copper pyrophosphate-based electrolyte offers an advantage over conventional alkaline-based electrolytes in that it removes cyanide pollution of the environment and hazards to human health.[4]In this study, the microanode was employed using a platinum wire(100 μm in diameter), while a copper substrate was employed as the cathode in the electrochemical deposition process. The micrometer copper columns were deposited using copper pyrophosphate-based electrolyte by varying the main electrochemical deposition factors, such as applied potential and pulse duty cycle. In addition The surface morphology of the deposited micrometer-scale copper columns was observed through scanning electron microscopy.REFERENCES[1] Suryavanshi, Abhijit P., and Min-Feng Yu. "Probe-based electrochemical fabrication of freestanding Cu nanowire array." Applied Physics Letters 88.8 (2006): 083103.[2] Madden, John D., and Ian W. Hunter. "Three-dimensional microfabrication by localized electrochemical deposition." Journal of microelectromechanical systems 5.1 (1996): 24-32.[3] Lin, J. C., et al. "Localized electrochemical deposition of micrometer copper columns by pulse plating." Electrochimica Acta 55.6 (2010): 1888-1894.[4] Chen, C-C. "A New Process for Cyanide-Free Copper Plating."Electroplating and Pollution Control 23.4 (2003): 10-11.

Performance of Magnéli phase Ti4O7 and Ti3+ self-doped TiO2 as oxygen vacancy-rich titanium oxide anodes: Comparison in terms of treatment efficiency, anodic degradative pathways, and long-term stability

This study compared hydrogen annealing and cathodic polarization (producing Magnéli phases and Ti3+ self-doped TiO2, respectively) as strategies to fabricate electrically conducting titanium oxides through oxygen non-stoichiometry creation for anodic water treatment. Electrochemical characterization techniques suggested that Ti4O7 best-suited for redox electrocatalysis among the Magnéli phases exhibited higher electrical conductivity than the self-doped TiO2. This aligned with the superiority of Ti4O7 over the self-doped TiO2 in chlorine evolution and anodic organic oxidation. Hydroxyl radical primarily contributed to anodic oxidation by two conductive titanium oxides at sulfate-based electrolyte, based on the retarding effects of radical scavengers, multi-activity assessment, electron paramagnetic resonance spectral features, and product distribution. Repetitive batch experiments and long-term tests in continuous operation mode demonstrated that self-doped TiO2 underwent more drastic performance reduction than Ti4O7. This accorded with the self-doped TiO2 being more vulnerable to activity loss, chemical alteration, and structural damage during prolonged application.

Co-Electrodeposition of Metallic Precursors for Cd-Doped Cu2ZnSnS4 (CZCTS) Kesterite Absorber for Photoelectrochemical Water Splitting

Electrodeposition is widely studied in the fabrication of semiconductors for solar application, because of the low cost and easy scalability of this technique. For instance, in the last decades large effort has been dedicated to the electrodeposition of Cu2ZnSnS4 (CZTS) through different approaches, including either direct co-electrodeposition of the sulfide, the deposition of metallic alloy precursors or by stacked elemental layer, depositing Cu, Zn and Sn in sequence, then converting it into kesterite with thermal treatment in sulfur atmosphere.1–4 While being a promising alternative to CIGS (CuInGaS2), thanks to the non-toxicity and higher abundance of its constituting elements, CZTS absorbers still encounter some difficulties to their integration of high-performance solar devices. In fact, the electronic and optical properties of the material are affected by the narrow stoichiometric window acceptable for kesterite formation, inducing the segregation of secondary phases, along with the formation of lattice defects that act as recombination sites.5 A reported strategy to suppress the latter limitation is to introduce doping elements such as Ag6 and Cd7,8, partially substituting metallic atoms in the semiconductor, Cu and Zn respectively. The larger atomic radii of these elements can prevent the formation of antisite defects such as CuZn, largely increasing the semiconductor performance7. Here we propose a synthesis route of CZCTS through the co-electrodeposition of a thin film Cu-Sn-Zn-Cd alloy followed by sulfurization treatment. The deposition on SLG/Mo substrate is achieved with a sulfate-based electrolyte with citrate complexing agents and performed in three-electrode potentiostatic conditions. Proper bath formulation is designed to obtain a desirable Zn-rich, Cu-poor composition, varying the degree of Zn substitution with Cd. An alternative 2-step deposition of CuZnSn/Cd stacked precursor is also investigated, as an attempt to compensate the effect of the low H+ adsorption energy of cadmium leading to the formation of blisters in the quaternary alloy. Sulfurized samples characterization shows the formation of good quality of kesterite CZCTS, in spite of the segregation of secondary phases on the surface. Cd doping of CZTS is observed through the characteristic shift of the main kesterite XRD peak (112) and an increase of the average size of grains. The photocurrent of finalized photocathodes with structure SLG/Mo/CZCTS/CdS/Pt is measured under 10 mW/cm2 AM 1.5 radiation reporting an improvement with respect to the undoped analogue, increasing the current density at 0 V vs RHE from -5.73 to -7.18 mA/cm2 in the best case.Bibliography Colombara, D. et al. Electrodeposition of kesterite thin films for photovoltaic applications: Quo vadis? Phys. Status Solidi Appl. Mater. Sci. 212, 88–102 (2015).Ge, J. & Yan, Y. Controllable Multinary Alloy Electrodeposition for Thin-Film Solar Cell Fabrication: A Case Study of Kesterite Cu2ZnSnS4. iScience 1, 55–71 (2018).Clauwaert, K., Binnemans, K., Matthijs, E. & Fransaer, J. Electrochemical studies of the electrodeposition of copper-zinc-tin alloys from pyrophosphate electrolytes followed by selenization for CZTSe photovoltaic cells. Electrochim. Acta 188, 344–355 (2016).Jiang, F. et al. Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation. J. Am. Chem. Soc. 137, 13691–13697 (2015).Polizzotti, A., Repins, I. L., Noufi, R., Wei, S. H. & Mitzi, D. B. The state and future prospects of kesterite photovoltaics. Energy Environ. Sci. 6, 3171–3182 (2013).Yuan, Z. K. et al. Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu- and Ag-Based Kesterite Compounds. Adv. Funct. Mater. 25, 6733–6743 (2015).Tay, Y. F. et al. Solution-Processed Cd-Substituted CZTS Photocathode for Efficient Solar Hydrogen Evolution from Neutral Water. Joule 2, 537–548 (2018).Su, Z. et al. Device Postannealing Enabling over 12% Efficient Solution-Processed Cu2ZnSnS4 Solar Cells with Cd2+ Substitution. Adv. Mater. 32, 1–12 (2020).

Investigation of black phosphorus anodic catalyst for electrolysis: Degradation of organics via a perchlorate-free oxidant activation

This study investigated the potential of a novel fabricated black phosphorus (BP) nanoparticle electrode as an alternative to noble metal-based catalysts for application in electrolysis. The BP electrode was compared with other conventional catalysts (boron-doped diamond (BDD) and a dimensional stable electrode (DSA)) under different electrolyte conditions for the generation of specific oxidants (e.g., OH•, HOCl, OCl−, SO4• -) in the bulk phase during electrolysis. In the presence of sulfate-based electrolyte, results on the electrochemical oxidation showed that the BP not only resulted in an 8-fold increase in the current efficiency compared to DSA, but also reduced energy consumptions by approximately 30-fold. Moreover, electrolysis using certain electrodes (i.e., BDD) under high current densities in the presence of chlorine-based electrolyte has been reported to be hazardous to the water system due to the generation of toxic chlorine oxyanions (i.e., perchlorate), which necessitates the operation of a post-treatment process. Likewise, application of the BDD electrode was confirmed to produce perchlorate under high current densities, while no by-product was generated by electrolysis with the BP electrode. Finally, multiple degradation pathways for selective water treatment was monitored under oxidation with the BP electrode. To the best of our knowledge, this study is the first to apply the novel fabricated BP electrode as the anodic catalyst for the treatment of a water system.

Enabling Reversible MnO2/Mn2+ Transformation by Al3+ Addition for Aqueous Zn-MnO2 Hybrid Batteries.

Aqueous rechargeable Zn-manganese dioxide (Zn-MnO2) hybrid batteries based on dissolution-deposition mechanisms exhibit ultrahigh capacities and energy densities due to the two-electron transformation between MnO2/Mn2+. However, the reported Zn-MnO2 hybrid batteries usually use strongly acidic and/or alkaline electrolytes, which may lead to environmental hazards and corrosion issues of the Zn anodes. Herein, we propose a new Zn-MnO2 hybrid battery by adding Al3+ into the sulfate-based electrolyte. The hybrid battery undergoes reversible MnO2/Mn2+ transformation and exhibits good electrochemical performances, such as a high discharge capacity of 564.7 mAh g-1 with a discharge plateau of 1.65 V, an energy density of 520.8 Wh kg-1, and good cycle life without capacity decay upon 2000 cycles. Experimental results and theoretical calculation suggest that the aquo Al3+ with Brønsted weak acid nature can act as the proton-donor reservoir to maintain the electrolyte acidity near the electrode surface and prevent the formation of Zn4(OH)6(SO4)·0.5H2O during discharging. In addition, Al3+ doping during charging introduces oxygen vacancies in the oxide structure and weakens the Mn-O bond, which facilitates the dissolution reaction during discharge. The mechanistic investigation discloses the important role of Al3+ in the electrolyte, providing a new fundamental understanding of the promising aqueous Zn-MnO2 batteries.

Potential-Dependent Passivation of Zinc Metal in a Sulfate-Based Aqueous Electrolyte.

Owing to its abundance, high theoretical capacity, and low electrode potential, zinc is one of the most important metallic anodes for primary and secondary batteries such as alkaline and zinc-air batteries. In the operation of zinc-based batteries, passivation of the anode surface plays an essential role because the electrode potential of zinc is slightly below that of the hydrogen evolution reaction. Therefore, it is important to scrutinize the nature of the passivation film to achieve anticorrosion inside batteries. Herein, the potential-dependent formation and removal of the passivation film during the deposition and dissolution of zinc metal in aqueous electrolytes are detected via electrochemical quartz crystal microbalance analysis. Film formation was not noticeable in hydroxide-based electrolytes; however, sulfate-based electrolytes induced potential-dependent formation and removal of the passivation film, enabling a superior coulombic efficiency of 99.37% and significantly reducing the rate of corrosion of the zinc-metal anodes. These observations provide insights into the development of advanced electrolytes for safe and stable energy-storage devices based on zinc-metal anodes.

Lowering the Energy Consumption of Zinc Electrowinning By Electrocatalysis of the Oxygen Evolution Reaction Using Manganese Oxides

Zinc has a wide range of commercial applications including but not limited to galvanizing iron and steel and production of various metal alloys such as brass and bronze. In hydrometallurgical processes, zinc electrowinning from sulfate-based electrolytes is the last step of zinc extraction in which high purity metallic zinc is electrodeposited from a highly acidic solution on an aluminum cathode. The electrowinning stage is very energy-intensive and responsible for approximately 80% of the power requirement of a zinc refinery (1). Thus, improving the energy efficiency and lowering the operating costs of zinc electrowinning are of primary significance. The oxygen evolution reaction (OER) overpotential on conventional lead-silver (Pb-Ag) anodes contributes to nearly 25% of the total electrowinning cell potential (2). Therefore, the high anodic OER overpotential places a heavy financial burden on zinc refining plants.The present study aims to evaluate novel anodic electrocatalysts incorporating MnO x in order to lower the anodic OER overpotential of the zinc electrowinning process. Anodically electrodeposited MnO x catalysts on Pb-Ag electrodes were prepared using galvanostatic and potentiodynamic polarizations. The OER catalytic activity and stability of MnOx electrodeposited Pb-Ag electrodes were evaluated in 160 g/L sulphuric acid solution with 3 g/L of manganese (II) and in the absence and presence of 0.3 g/L of chloride ion at 35°C, using a standard three-electrode setup. The electrolyte composition and operating conditions were selected such that to be directly applicable to the industrial zinc electrowinning process. The OER activity of the MnOx electrodeposited electrodes was investigated through potentiodynamic polarization and 72-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density. Finally, the activity of MnOx electrodeposited Pb-Ag electrodes was explored in a full zinc electrowinning cell through 24-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density.The OER potential variations of the bare Pb-Ag and MnO x electrodeposited Pb-Ag anodes during the 72-hour galvanostatic polarization are shown in Fig. 1. In the absence and presence of chloride ions, the three MnO x electrodeposited Pb-Ag electrodes are observed to reduce the anodic potential by maximum of 150 mV and 80 mV, respectively. Investigation of these novel electrodes in the full-cell zinc electrowinning operation corroborated the half-cell experiments, revealing a maximum of 130 mV reduction in cell potential at 50 mA/cm2 superficial current density and in the presence of 0.3 g/L of chloride ion. Thus, this work demonstrates that MnO x electrodeposited Pb-Ag anodes have great capacity to lower the power consumption of the zinc electrowinning process.Fig. 1. OER activity and stability comparison under galvanostatic polarization for four anodes: bare Pb-Ag (baseline) and three MnOx electrodeposited Pb-Ag anodes prepared via linear scan voltammetry (LSV), constant current density (CCD), and cyclic voltammetry (CV). Superficial current density: 50 mA/cm2. Electrolyte:160 g/L H2SO4 with 3 g/L Mn2+ and 0.3 g/L Cl- at 35°C.References A. C. Scott, R. M. Pitbaldo, G.W. Barton, A. R. Ault, J. Appl Electrochem, 18, 120–127 (1988). Schmachtel, M. Toiminen, K. Kontturi, O. Forsen, M. H. Barker, J. Appl Electrochem, 39, 1835–1848 (2009). Figure 1

Lowering the Energy Consumption of Zinc Electrowinning By Electrocatalysis of Oxygen Evolution Reaction Using Manganese Oxides

Zinc has a wide range of commercial applications including but not limited to galvanizing iron and steel and production of various metal alloys such as brass and bronze. In hydrometallurgical processes, zinc electrowinning from sulfate-based electrolytes is the last step of zinc extraction in which high purity metallic zinc is electrodeposited from a highly acidic solution on an aluminum cathode. The electrowinning stage is very energy-intensive and responsible for approximately 80% of the power requirement of a zinc refinery (1). Thus, improving the energy efficiency and lowering the operating costs of zinc electrowinning are of primary significance. The oxygen evolution reaction (OER) overpotential on conventional lead-silver (Pb-Ag) anodes contributes to nearly 25% of the total electrowinning cell potential (2). Therefore, the high anodic OER overpotential places a heavy financial burden on zinc refining plants.The present study aims to evaluate novel anodic electrocatalysts incorporating MnO x in order to lower the anodic OER overpotential of the zinc electrowinning process. Anodically electrodeposited MnO x catalysts on Pb-Ag electrodes were prepared using galvanostatic and potentiodynamic polarizations. The OER catalytic activity and stability of MnOx electrodeposited Pb-Ag electrodes were evaluated in 160 g/L sulphuric acid solution with 3 g/L of manganese (II) and in the absence and presence of 0.3 g/L of chloride ion at 35°C, using a standard three-electrode setup. The electrolyte composition and operating conditions were selected such that to be directly applicable to the industrial zinc electrowinning process. The OER activity of the MnOx electrodeposited electrodes was investigated through potentiodynamic polarization and 72-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density. Finally, the activity of MnOx electrodeposited Pb-Ag electrodes was explored in a full zinc electrowinning cell through 24-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density.The OER potential variations of the bare Pb-Ag and MnO x electrodeposited Pb-Ag anodes during the 72-hour galvanostatic polarization are shown in Fig. 1. In the absence and presence of chloride ions, the three MnO x electrodeposited Pb-Ag electrodes are observed to reduce the anodic potential by maximum of 150 mV and 90 mV, respectively. Investigation of these novel electrodes in the full-cell zinc electrowinning operation corroborated the half-cell experiments, revealing a maximum of 80 mV reduction in cell potential at 50 mA/cm2 superficial current density and in the presence of 0.3 g/L of chloride ion. Thus, this work demonstrates that MnO x electrodeposited Pb-Ag anodes have great capacity to lower the power consumption of the zinc electrowinning process.Fig. 1. OER activity and stability comparison under galvanostatic polarization for four anodes: bare Pb-Ag (baseline) and three MnOx electrodeposited Pb-Ag anodes prepared via linear scan voltammetry (LSV), constant current density (CCD), and cyclic voltammetry (CV). Superficial current density: 50 mA/cm2. Electrolyte:160 g/L H2SO4 with 3 g/L Mn2+ and 0.3 g/L Cl- at 35°C.

Insight into the unusual intercalation/deintercalation phenomena of alkali cations in the layered manganese oxide for electrochemical capacitors

The unusual intercalation phenomena of alkali cations (Li+, Na+, K+, Rb+, and Cs+) in the sulfate-based electrolyte on the electrochemical behavior of birnessite-type layered-manganese oxide nanosheets with Li-intercalated cation (Li-MnO2) were studied by in situ electrochemical synchrotron X-ray Absorption spectroscopy. Li-MnO2 exhibits the highest charge storage capacity in Na2SO4(aq), followed by Li2SO4, K2SO4, and Cs2SO4, respectively. Whilst, it does not exhibit the charge-storage characteristics in Rb2SO4 as the solvated Rb+ could not intercalate into the lamellar structure of birnessite. Understanding unusual intercalation phenomena can be useful for further development of the electrochemical capacitors.

Electrochemical Oxidation-Membrane Distillation Hybrid Process: Utilizing Electric Resistance Heating for Distillation and Membrane Defouling through Thermal Activation of Anodically Formed Persulfate.

This study reports distillation-based salt removal by Ohmic heating in a hybrid process, in which electrochemical oxidation (EO) and direct contact membrane distillation (DCMD) are performed sequentially. In addition to anodically destructing the organics, the hybrid process also separated the sulfate-based electrolytes from treated water through distillation, without consuming external energy, owing to the temperature of the aqueous sulfate solution being elevated to 70 °C via resistive heating. The hybrid process treated organic compounds in a nonselective fashion, whereas DCMD alone did not completely reject (semi)volatile organics. Integrating EO with DCMD made the hybrid process resistant toward the wetting phenomenon; the process exhibited a steady distillate flux and salt rejection as the initial loading of amphiphilic sodium dodecyl sulfate was increased to 0.3 mM. Anodic persulfate formation from the sulfate and Ohmic heating caused an in situ yield of the sulfate radical in the feed solution; this eliminated membrane fouling, according to the observation that the water flux, which was drastically reduced upon adding alginate, was recovered immediately after an electric current was applied. The hybrid process concurrently decomposed spiked organics and removed naturally present inorganic ions in actual flue gas desulfurization wastewater, without an external supply of electrolyte and heat energy.

Low Temperature Performance of MnOx@Carbon Nanofoam-Based Ecs with Neutral pH-Based Aqueous Electrolytes

Electrochemical capacitors (ECs) comprising high-surface-area carbon electrodes and nonaqueous electrolytes offer many attractive performance attributes including long cycle life and the ability to operate at low temperatures (–40⁰C), yet their energy density is ultimately limited by reliance on the double-layer charge-storage mechanism. Asymmetric EC configurations that include pseudocapacitive materials (e.g., transition metal oxides) offer the opportunity to increase energy density while also using safer and cheaper aqueous electrolytes. We have shown that with the appropriate electrode structure and electrolyte additives, the additional charge stored via pseudocapacitance is delivered at EC-like rates over 1000 cycles with minimal capacitance fade. To further prove the practical feasibility of such aqueous-electrolyte ECs, we turned our attention to low-temperature performance, focusing on aqueous electrolyte compositions containing lithium or sodium cations and sulfate or nitrate anions. We characterized pertinent bulk properties (e.g., freezing point and ionic conductivity) of down-selected electrolytes and found that the anion dominates the freezing point, with sulfate-based electrolytes having a freezing point of –45oC, while nitrate-based electrolytes have a freezing point of –35oC. The ionic conductivities ranged from 63 to 136 mS cm-1 at 20oC, conductive enough to support high-rate operation. To assess the impact of temperature on performance as a function of electrolyte composition, we fabricated symmetric pouch cells comprised of MnOx@carbon nanofoam electrodes, evaluating the resulting devices via cyclic voltammetry and electrochemical impedance spectroscopy over a wide temperature range (25⁰C to –45⁰C). All ECs exhibited a gradual decrease in capacitance as the temperature decreased; however, capacitance was recovered upon warming to 25°C for all electrolyte compositions. We found that ECs with Li2SO4-based electrolytes (neat or mixed composition) were operational at temperatures as low as –35°C, revealing that these electrolytes are competitive with the nonaqueous electrolytes used in conventional double layer capacitors.

The initial characteristics of the polypyrrole based aqueous rechargeable batteries with supercapattery characteristics

The electrochemically synthesized polypyrrole (PPy) is investigated as a possible active material of the low-cost aqueous based secondary power sources in combination with zinc, lead oxide, and lead sulfate. The discharge capacity of the polypyrrole in the chloride-based electrolyte (for the Zn|PPy cell) is in the range 110 mAh g−1 of PPy, while in the sulfate-based electrolyte ∼150 mAh g−1 of PPy (for the PbSO4|PPy and PPy|PbO2 cells), which is close to the theoretically calculated values. Electrochemical and electrical parameters, reactions in the cells, specific capacity, specific capacitance, energy, and power, for the Zn|PPy, PPy|PbO2 and PbSO4|PPy cells are determined. In addition, the energy efficiency, for the considered systems is estimated. Obtained values of the specific power and energy, could classified investigated systems as a battery type hybrid superacapacitors or “supercapattery”.

Copper Rich Cu1-xNix Alloys (0.05 < x < 0.15) Electrodeposited from Acid Sulfate-Based Electrolyte with Benzotriazole Additive for Microbump Metallization for 3D Stacked Integrated Circuits

In this paper we report on electrodeposition of CuNi alloys with low Ni content for applications in three-dimensional stacking of integrated circuits (SIC). For practical reasons related to compatibility with SIC processing, a common sulfate-based electrolyte solution was chosen and the high copper/low nickel content in the deposited alloys was achieved through the introduction of organic additive benzotriazole (BTA). BTA is known as a strong inhibitor for Cu deposition, but its effects on CuNi alloy deposition were not known before. We hypothesized that, in addition to bringing the onset potential of Cu closer to that of Ni deposition, the slower diffusion through the BTA passivation layer could enable improved control of the composition of the deposited alloy as well as the current distribution over the substrate. Our hypotheses were tested through systematic electrochemical measurements combined with ex-situ imaging and chemical analysis techniques. As such, CuNi alloys with Ni content between 5–15 at.% were successfully fabricated from a sulfate-based CuNi electrolyte solution with BTA as an organic additive.

High quality, low-oxidized graphene via anodic exfoliation with table salt as an efficient oxidation-preventing co-electrolyte for water/oil remediation and capacitive energy storage applications

The production of graphene through anodic exfoliation of graphite in water is regarded as a competitive approach in the efforts to scale-up the manufacturing of this two-dimensional material for different practical uses. However, issues related to oxidative attack of the nanosheets inherent to this delamination process have traditionally precluded the attainment of high quality materials, with the use of proper electrolyte additives as oxidation-preventing agents being proposed as a possible way out. Here we demonstrate that sodium chloride (table salt) can be used as a highly efficient additive (co-electrolyte) of common sulfate-based electrolytes, yielding anodically exfoliated graphene with minimal oxidation (O/C ratio ∼0.02–0.03) and thus a high structural quality. As an oxidation-preventing co-electrolyte, sodium chloride clearly outperformed other tested additives, including sodium borohydride, sulfite, citrate, bromide and iodide, ascorbic acid or ethanol, as well as other recently reported chemical species of a more complex nature and/or less readily available. The apparently contradicting ability of the chloride anion to avert oxidation of anodic graphene without negatively interfering with the exfoliation process itself was also discussed and ultimately ascribed to the different chemical reactivity of graphite edges and basal planes. The as-prepared, low-oxidized graphene exhibited a notable adsorption capacity toward organic dyes in aqueous solution (e.g., ∼450mgg−1 for methyl orange), a substantial ability to absorb oils and non-polar organic solvents (15–30gg−1), and displayed a good capacitive energy storage behavior (e.g., ∼120Fg−1 at 0.1Ag−1), all without the need of any post-processing steps that are so common for graphene-based materials. Overall, the demonstration that low-oxidized anodic graphene can be obtained by resorting only to inexpensive and widely available reagents should facilitate the implementation of this methodology in the industrial manufacturing of high quality graphene for several applications.

Low-Temperature Performance of Symmetric MnOx-Carbon Nanofoam-Based Ecs with Mild-pH Aqueous Electrolytes

Electrochemical capacitors, ECs, should provide high performance over the broadest range of operating temperatures which is primarily determined by the properties of the electrolyte (freezing and boiling points, ionic conductivity and salt solubility as a function of temperature, flash point for flammable solvents). In the case of mild-pH aqueous electrolytes, where flammability is a non-issue, the sub-ambient temperature performance is the most critical factor. En route to demonstrating the performance of aqueous-electrolyte ECs at low temperature, we have characterized both the bulk thermal properties of single and multi-component electrolytes and their behavior when used in EC pouch cells. The ionic conductivities of bulk electrolytes with a fixed cation concentration of 5 M for single-component (e.g. Li2SO4, NaNO3) and multi-component electrolytes (e.g. Li2SO4 + NaNO3) ranged from 63 to 136 mS cm-1 at 20oC. The freezing points of these electrolytes were measured with differential scanning calorimetry. It was found that the anion dominates the freezing-point behavior, with sulfate-based electrolytes supporting freezing points down to –45oC and nitrate-based electrolytes down to –35oC. To assess the impact of temperature on performance as a function of electrolyte composition, we fabricated symmetric pouch cells comprising MnOx-carbon nanofoam electrodes and tested them over the temperature range of 25oC to –45oC in an environmental chamber. All ECs exhibited a gradual decrease in capacitance as the temperature decreased; however, upon re-warming to 25°C, the capacitance was recovered, indicating that freezing does not cause significant degradation to electrode or separator components. Aqueous electrolytes comprising mixtures of Li2SO4 and NaNO3 yielded the best combination of depressed freezing point and ionic conductivity among the compositions evaluated in EC pouch cells.