Anode Production Research Articles

Life cycle safety issues of lithium metal batteries: A perspective

AbstractThe rising lithium metal batteries (LMBs) demonstrate a huge potential for improving the utilization duration of energy storage devices due to high theoretical energy density. Benefiting from the designs in the electrolyte, interface, and lithium host, several attempts have been made in the commercial application of LMBs. However, the application of lithium anode introduces additional safety risks and potential catastrophic accidents due to the high activity of lithium metal and dendrite during the electrochemical cycles. A comprehensive understanding of challenges and design issues on the safety hazards of LMBs in life cycle management is imperative for safe and commercial applications of LMBs. This paper first reviews emerging key safety issues and promising corresponding enhancements of LMBs during their production, utilization, and recycling. The wet air instability of lithium metal anode and gas production during activation have undoubtedly become the most intractable problems in LMBs production. It is necessary to use spraying technology to build a good protection layer upon lithium metal anode. Then, the growth of lithium dendrites poses a higher challenge to the utilization of LMBs, which requires the design of better electrolyte, anode skeleton, and other strategies as well as the prediction of LMBs life through big data and other methods. As for LMBs recovery, it is of great significance to choose the solvent to effectively control the consumption rate and temperature of highly reactive lithium metal powder. At last, further appeals and improvements are proposed for inspiring more related research to push forward the commercial use of LMBs.

Ti/Ti4O7 Anodes for Efficient Electrodeposition of Manganese Metal and Anode Slime Generation Reduction.

Preventing lead-based anodes from causing high-energy consumption, lead pollution, and harmful anode slime emission is a major challenge for the current electrolytic manganese metal industry. In this work, a Ti4O7-coated titanium electrode was used as anode material (Ti/Ti4O7 anode) in manganese electrowinning process for the first time and compared with a lead-based anode (Pb anode). The Ti/Ti4O7 anode was used for galvanostatic electrolysis; the cathodic current efficiency improved by 3.22% and energy consumption decreased by 7.82%. During 8 h of electrolysis, it reduced 90.42% solution anode slime and 72.80% plate anode slime formation. Anode product characterization and electrochemical tests indicated that the Ti/Ti4O7 anode possesses good oxygen evolution activity, and γ-MnO2 has a positive catalytic effect on oxygen evolution reaction (OER), which inhibited anode Mn2+ oxidation reaction and reduced the formation of anode slime. In addition, the low charge-transfer resistance, high diffusion resistance, and dense MnO2 layer of the anode blocked the diffusion path of Mn3+ in the system and inhibited the formation of anode slime. The Ti/Ti4O7 anode exhibits excellent electrochemical performance, which provides a new idea for the selection of novel anodes, energy savings and emission reduction, and the establishment of a new mode of clean production in the electrolytic manganese metal industry.

Graphene coated lithium foil anode enables long cycle life Li metal pouch cells

Among various technologies that go beyond lithium-ion batteries, lithium metal batteries (LMBs) have been intensively studied as the next generation of high-energy battery technology. However, achieving scalable production of dendrite-free lithium metal anodes (LMAs) for practical application is still a formidable challenge. Herein, we propose a simple and feasible method to modify lithium foil with graphene coatings, which is expected to be used in practical applications on a large scale. Graphene has a high specific surface area and excellent electrical conductivity, which can disperse current density, induce uniform Li deposition, and reduce the generation of dendrites and dead lithium. Meanwhile, the porous graphene coating layer is beneficial to the continuous compensation of irreversible active Li loss by the Li foil underneath the graphene coating. As a result, pouch cells using graphene coated Li anode display superior cyclic stability comparing to the cell with bare Li anode. The cell with a high areal capacity of 4 mAh cm−2 reaches a high capacity retention of 76% after 470 charge/discharge cycles at a current density of 0.1C.

(Keynote) Experimental Insights for Extra-Terrestrial Application of Molten Oxide Electrolysis

Molten oxide electrolysis (MOE) has been considered for several decades for oxygen generation from extra-terrestrial oxides. It consists in the electrolytic decomposition of the rocks or soils, which are mixture of the common earth oxides (silica, iron oxide(s), alumina, magnesia...). Therein the oxides mixture is acting as the electrolyte, in the molten state. The target anodic product is oxygen gas, and the cathodic product is a metal. In one version of MOE, the temperature is high enough to sustain the production of a liquid metal, offering the opportunity to conceive a fully continuous process thanks to periodic tapping of the cathodic product. A key attribute of such approach is the high current density (productivity) that can be anticipated thanks to the high concentration of oxygen and metal present in the electrolyte. This leads to electrochemical engineering questions that are not commonly discussed in other electrolysis methods. This presentation offers to review some of the prior findings related to the underlying thermodynamic of the process, as well as the oxygen evolution and transport phenomena that support the development of MOE. Recent findings combining a container-less method and advanced electrochemical techniques will be presented.

A “Green” Reaction Cycle Pathway for Synthesizing Metal Oxide Quantum Dots

Synthesis of highly stable quantum dots (QDs) is always a challenge for researchers in nanomaterial community because of involved complexities of the process time and steps. In the past few years, we have demonstrated a simple and single step synthesis process for a range of metal oxide (MO) QDs using plasma-induced non-equilibrium electrochemistry (PiNE).1 , 2 , 3 PiNE is a new and emerging technique based on electrochemical process taking place in liquids from plasma interaction.4 This method is rapid and produces highly stable QDs starting from a metal foil and ethanol as electrolyte. As MO QDs semiconductors in general are a promising candidate for energy harvesting application mainly from their nanoscale effects.5 , 6 In this work, we will present the general applicability of this method for a range of metal oxides and the provide more an in-depth case study for CuO QDs providing details of the reaction mechanisms. An extensive analysis of the solution along with the quantum dots was carried out with nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass (GC-MS) spectroscopy, Fourier transform infra-red spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, pH and the plasma-ethanol interface using optical emission spectroscopy. Thus, the study discloses important aspects of plasma interactions with a non-aqueous medium particularly the trace products and QD purity shows the entire process is a ‘green’ synthesis cycle.7 Reference (1) Ni, C.; Carolan, D.; Rocks, C.; Hui, J.; Fang, Z.; Padmanaban, D. B.; Ni, J.; Xie, D.; Maguire, P.; Irvine, J. T. S.; Mariotti, D. Microplasma-Assisted Electrochemical Synthesis of Co 3 O 4 Nanoparticles in Absolute Ethanol for Energy Applications. Green Chem. 2018, 20 (9), 2101–2109. https://doi.org/10.1039/C8GC00200B.(2) Ni, C.; Carolan, D.; Hui, J.; Rocks, C.; Padmanaban, D.; Ni, J.; Xie, D.; Fang, Z.; Irvine, J.; Maguire, P.; Mariotti, D. Evolution of Anodic Product from Molybdenum Metal in Absolute Ethanol and Humidity Sensing under Ambient Conditions. Cryst. Growth Des. 2019, 19 (9), 5249–5257. https://doi.org/10.1021/acs.cgd.9b00646.(3) Chakrabarti, S.; Carolan, D.; Alessi, B.; Maguire, P.; Svrcek, V.; Mariotti, D. Microplasma-Synthesized Ultra-Small NiO Nanocrystals, a Ubiquitous Hole Transport Material. Nanoscale Adv. 2019. https://doi.org/10.1039/C9NA00299E.(4) Mariotti, D.; Patel, J.; Švrček, V.; Maguire, P. Plasma-Liquid Interactions at Atmospheric Pressure for Nanomaterials Synthesis and Surface Engineering. Plasma Process. Polym. 2012, 9 (11–12), 1074–1085. https://doi.org/10.1002/ppap.201200007.(5) Velusamy, T.; Liguori, A.; Macias-Montero, M.; Padmanaban, D. B.; Carolan, D.; Gherardi, M.; Colombo, V.; Maguire, P.; Svrcek, V.; Mariotti, D. Ultra-Small CuO Nanoparticles with Tailored Energy-Band Diagram Synthesized by a Hybrid Plasma-Liquid Process. Plasma Process. Polym. 2017, 14 (7), 1600224. https://doi.org/10.1002/ppap.201600224.(6) McGlynn, R.; Chakrabarti, S.; Alessi, B.; Moghaieb, H. S.; Maguire, P.; Singh, H.; Mariotti, D. Plasma-Induced Non-Equilibrium Electrochemistry Synthesis of Nanoparticles for Solar Thermal Energy Harvesting. Sol. Energy 2020, 203 (April), 37–45. https://doi.org/10.1016/j.solener.2020.04.004.(7) Padmanaban, D. B.; McGlynn, R.; Byrne, E.; Velusamy, T.; Swadźba-Kwaśny, M.; Maguire, P.; Mariotti, D. Understanding Plasma–Ethanol Non-Equilibrium Electrochemistry during the Synthesis of Metal Oxide Quantum Dots. Green Chem. 2021, 23 (11), 3983–3995. https://doi.org/10.1039/D0GC03291C.

Construction of desolvated ionic COF artificial SEI layer stabilized Zn metal anode by in-situ electrophoretic deposition

Aqueous zinc-ion batteries (AZIBs) have attracted tremendous attention due to their cost-effectiveness, environmental-friendliness, and intrinsic safety. However, the spontaneous surface corrosion and uncontrolled dendrite growth of AZIBs severely restrict its practical application. Herein, we develop an artificial solid electrolyte interphase (SEI) with ionic covalent-organic-framework (iCOF) nanosheets for Zn anode protection. The iCOF nanosheets form an artificial SEI layer with porous and abundant zincophilic sites through in-situ electrophoretic deposition (ED) technique, which allows for efficient mass and charge transfer. The iCOF-ED SEI layer not only facilitates a uniform Zn2+ flux but regulates the Zn2+ solvation shell, resulting in a stable and homogeneous Zn2+ deposition. This novel iCOF-ED SEI layer enables high stability for over 1000 h (with ultralow overpotential ∼ 50 mV) at 1 mA cm−2 in symmetric cells and enhances cycling stability over 1100 cycles (with high average coulombic efficiency of 99.9 %) at 2 A g−1 in half cells. This finding provides a facile and promising route for the scalable production of anodes with artificial SEI, thus promoting the development of high-performance AZIBs.

Correlating the Valence State with the Adsorption Behavior of a Cu-Based Electrocatalyst for Furfural Oxidation with Anodic Hydrogen Production Reaction.

The low-potential furfural oxidation reaction (FFOR) on a Cu-based electrocatalyst can produce H2 at the anode, thereby providing a bipolar H2 production system with an ultra-low cell voltage. However, the intrinsic activity and stability of the Cu-based electrocatalyst for the FFOR remain unsatisfactory for practical applications. This study investigates the correlation between the valence state and the adsorption behavior of the Cu-based electrocatalyst in furfural oxidation. Cu0 is the adsorption site with low intrinsic activity. Cu+ , which exist in the form of Cu(OH)ads in alkaline electrolyte, has no adsorption ability but can improve the performance of Cu0 by promoting adsorption of FF. Moreover, a mixed-valence Cu-based electrocatalyst (MV Cu) with high intrinsic activity and stability is prepared electrochemically. With the MV Cu catalyst, the assembled dual-side H2 production electrolyzer has a low electricity requirement of only 0.24 kWh·mH2 -3 at an ultra-low cell voltage of 0.3V, and it exhibits sufficient stability. This study not only correlates the valence state with the adsorption behavior of the Cu-based electrocatalyst for the low-potential FFOR with anodic H2 production but also reveals the mechanism of deactivation to provide design principles for Cu-based electrocatalysts with satisfactory stability. This article is protected by copyright. All rights reserved.

Research on the Internal Defect Detection Algorithm of Pre-baked Anode Based on Machine Learning

To improve the quality of the pre-baked anode products, it is necessary to check the internal cracks of the pre-baked anode. The developed automatic knocking device is used to determine whether there are cracks in the pre-baked anode by using the obtained sound signal of the pre-baked anode knocking and machine learning. In this paper, first, the Fast Fourier Transform (FFT) is used to transform the sound signal to obtain 10 features in the frequency domain. Then, the main features of the pre-baked anode are obtained by principal component analysis (PCA). Next, the binary classification of support vector machine (SVM) is used to determine whether the pre-baked anode contains cracks, and finally, satisfactory results are obtained.

Elucidating mechanistic background of the origin and rates of peroxide formation in low temperature proton exchange fuel cells

Degradation of electrode-membrane assembly of the low-temperature hydrogen fuel cells represents one of the main obstacles in wider adoption of these clean and efficient electrochemical sources of electrical energy. Chemical degradation of proton exchange membrane is initiated by hydrogen peroxide formation, which forms in the fuel cell as a by-product to water in oxygen reduction reaction and decomposes to reactive radical species, damaging to the membrane chemical structure. Depending on the operating conditions of the fuel cell, the source of hydrogen peroxide can be either cathode, anode, or, as we argue in the paper, also the Pt particles in the membrane, which originate from the cathode catalyst dissolution, diffusion into the membrane and redeposition of Pt ions inside the membrane. In the paper we propose a mathematical model of intertwined physical processes in membrane and catalyst layer, aimed at unifying the description of hydrogen peroxide formation throughout entire membrane-electrode assembly at any fuel cell operating conditions. The model results, compared to experimental data, indicate that Pt particles inside the membrane can indeed be an important source of hydrogen peroxide in aged fuel cells. For a fresh fuel cell, numerical simulation using proposed model show that hydrogen peroxide can be formed at either cathode or anode, depending on the fuel cell operating condition, but with anode production being more prominent in standard fuel cell operating conditions.

Impact of Pitch Modification on Anode Properties: Effect of Additive Type.

Aluminum is one of the major industries in Canada. The main challenges facing the aluminum industry are carbon loss, energy use, greenhouse gas emissions, cell performance, and production costs, especially for high-amperage cells. The quality of carbon anodes plays a major role in the stability of cell operation and energy consumption. Anodes are made from petroleum coke, rejected green and baked anodes and butts, as well as coal tar pitch, which binds all of the particles. Although the industry depends on a steady supply of high-quality anodes, the availability of quality anode raw materials-coke and pitch-has decreased. A means of improving raw material quality is to modify their properties. In this work, using two additives, low- and high-quinoline insoluble (LQI and HQI) pitches were modified. These additives enrich the surface functional groups of the pitch, thereby increasing coke-pitch interactions. Various additive concentrations and pitch percentages were assessed. It is found that the choice of additive type has a marked effect on pitch properties, with different additives improving different pitches. Additive 1 is suitable for the HQI pitch, whereas additive 2 modifies the LQI pitch better. Anode properties are improved by modifying one of the pitches, whereas modifying the other pitch affects the anode quality to a lesser extent. Thus, the results showed that the modification of an already good-quality pitch (LQI pitch) does not significantly affect the anode quality. On the other hand, the modification of the inferior-quality pitch (HQI pitch) improved the anode quality and decreased the optimum pitch percentage necessary to obtain good anodes compared to the percentage of the LQI pitch needed. This would help decrease the anode production cost. The wettability tests give an indication of if the additive has the potential to improve the coke-pitch interactions, but it cannot predict the effect of pitch percent.

Maximizing the utilization of lignocellulosic biomass: Process development and analysis

Herein, an innovative strategy is proposed for the manufacture of biochemicals (dissolving pulp, furfural, high-purity lignin, and acetic acid) from lignocellulosic biomass. Utilizing sulfuric acid as the catalyst and a mixture of water and γ-valerolactone (GVL) as the solvent, the biomass was successfully fractionated into four major components: 1) cellulose, which was converted into dissolving pulp for fiber production; 2) hemicellulose, which was decomposed into furfural, a valuable platform chemical; 3) lignin, which was purified intensively for the production of carbon foams or battery anodes; and 4) acetate, which was converted into acetic acid, a chemical that is potentially useful as a H2 carrier and in H2 production. Separation subsystems were developed to recover the water and GVL mixture effectively for reuse in biomass fractionation and to separate cellulose, hemicellulose, lignin, and acetate for further treatment. To reduce the energy requirements, a heat pump was introduced and heat integration was conducted. The integrated process achieved a positive NPV ($19.9 million), making our process economically viable against initial uncertainties and high risks related to the project. Furthermore, dissolving pulp production was found to be the major environmental contributor accounting for 47.1% of fossil depletion and 36.4% of climate change.

Semi‐Dry Extrusion‐Based Processing for Graphite Anodes: Morphological Insights and Electrochemical Performance

To improve the sustainability of large‐scale battery production, it is important to find affordable, energy‐efficient processing strategies. Additionally, to achieve electrochemical performances with good rate capability and cycling stability, it is important to understand the link between the processing strategy and the resulting anode morphology. Herein, a novel, low‐solvent, extrusion‐based strategy is employed for the production of graphite anodes. Furthermore, a comparative analysis is conducted between semi‐dry processed electrodes and conventionally manufactured anodes, focusing on structural parameters such as parameter distribution, ionic resistances, and rate capability. Besides, various screw configurations are employed during the semi‐dry process, and it is observed that higher energy input during mixing resulted in an increase in the surface area of the anode. Moreover, it is noted that an increased surface area correlated with enhanced rate capability during cycling. This finding highlights the advantages of employing low‐solvent, extrusion‐based processing methods. Nevertheless, excessively high surface areas lead to an increase in the electrolyte/electrode interface area, resulting in the formation of an undesirable solid–electrolyte interphase that hampers discharge capacity and cycling stability. Hence, it is crucial to strike a balance between the electrode's microstructure, including particle structures, and its electrochemical performance.

Recycling Silicon Waste from the Photovoltaic Industry to Prepare Yolk–Shell Si@void@C Anode Materials for Lithium–Ion Batteries

Silicon is considered to have significant potential for anode materials in lithium–ion batteries (LIBs) with a theoretical specific capacity of 4200 mAh g−1. However, the development of commercial applications is impacted by the volume shift that happens in silicon when charging and discharging. In this paper, a yolk–shell–structured Si@void@C anode material has been developed to address this problem. The silicon nanoparticle yolk material is obtained by recycling kerf loss (KL) Si waste from the process of slicing silicon block casts into wafers in the photovoltaic industry; the carbon shell is prepared by a hydrothermal method with glucose, and the sacrificial interlayer is Al2O3. The produced material is employed in the production of anodes, exhibiting a reversible capacity of 836 mAh g−1 at 0.1 A g−1 after 100 cycles, accompanied by a Coulomb efficiency of 71.4%. This study demonstrates an economical way of transforming KL Si waste into materials with an enhanced value for LIBs.

Cover Feature: Simultaneous Anodic and Cathodic Formate Production in a Paired Electrolyzer by CO2 Reduction and Glycerol Oxidation (ChemSusChem 11/2023)

The Cover Feature shows a representation of the advantage of the combined use of two waste products, namely glycerol, a by-product of the biodiesel production, and CO2, a pollutant from factories exhausts, for the production of formate on both sides of a paired electrolyzer. More information can be found in the Research Article by J. Junqueira et al.

Paired electrochemical synthesis of formate via oxidation of glycerol and reduction of CO2 in a flow cell reactor

The conventional anodic oxygen evolution (OER) in electrochemical CO2 reduction (CO2R) needs to be replaced as it accounts for a major share in energy consumption while being a product of little to no value. In this work, we replace OER by glycerol oxidation reaction (GOR) to synthesize products such as formate, lactate and glycolate. Hereby, for the first time, GOR was successfully paired with cathodic CO2R to formate in a flow reactor at a significant current density of 50 mA/cm2 producing value added anode products with a simultaneously reduced cell voltage. Using a porous platinum anode, GOR reduced the anode potential as well as cell potential by ∼1 V compared to OER. We report an anodic Faraday efficiency (FE) of 30% to ∼53% for liquid products, of which lactate dominates. The structure of the electrode has a significant impact on the dominant product as mainly formate is synthesized on a planar electrode, where the cummulated FE for all liquid products is up to 76%. The concurrent FE to formate at cathode and anode reached a values of up to 74% and 30% respectively and 66% and 76%, respectively, considering all value-added products. By successfully pairing GOR with CO2R in a flow cell reactor, this work marks an important step towards energy-efficient and economically viable processes.

Paired Electrosynthesis of Formic Acid from CO2 and Formaldehyde from Methanol

Electrochemical carbon dioxide (CO2) reduction provides a pathway to sustainable chemicals. However, the high electrical energy demand is still a major challenge. Cathodic (CO2) reduction is typically paired with the anodic oxygen evolution reaction (OER), which is energy intensive with limited added value. In this experimental work, we replace OER with partial methanol oxidation to reduce the energy demand while producing formaldehyde and formic acid as value-added chemicals. We investigate methanol oxidation on metallic and oxidized platinum and the paired process with CO2 reduction to formic acid in an electrochemical flow cell. Methanol oxidation on oxidized platinum was more selective to formaldehyde than on metallic platinum but required a higher potential. In the paired process, we achieved a current efficiency for formaldehyde of up to 58% on oxidized platinum at 75 mA cm–2 and 1.8 V vs RHE reaching a concentration of 1.14 mol L–1 formaldehyde. The current efficiency for formaldehyde and formic acid combined reached up to 89%. Methanol oxidation was not affected by pairing, while the current efficiency of CO2 reduction decreased. We report the first production of formaldehyde beyond mechanistic studies by electrochemical methanol oxidation and demonstrate paired CO2 reduction with formaldehyde as primary anodic product.

Simultaneous Anodic and Cathodic Formate Production in a Paired Electrolyzer by CO2 Reduction and Glycerol Oxidation.

Electrochemical CO2 conversion is a key technology to promote the production of carbon-containing molecules, alongside reducing CO2 emissions leading to a closed carbon cycle economy. Over the past decade, the interest to develop selective and active electrochemical devices for electrochemical CO2 reduction emerged. However, most reports employ oxygen evolution reaction as an anodic half-cell reaction causing the system to suffer from sluggish kinetics with no production of value-added chemicals. Therefore, this study reports a conceptualized paired electrolyzer for simultaneous anodic and cathodic formate production at high currents. To achieve this, CO2 reduction was coupled with glycerol oxidation: a BiOBr-modified gas-diffusion cathode and a Nix B on Ni foam anode keep their selectivity for formate in the paired electrolyzer compared to the half-cell measurements. The paired reactor here reaches a combined Faradaic efficiency for formate of 141 % (45 % anode and 96 % cathode) at a current density of 200 mA cm-2 .

Direct extracellular electron transfer to an indium tin doped oxide electrode via heme redox reactions in Desulfovibrio ferrophilus IS5

Soluble redox mediators have been hypothesized to play a major role in cellular electron transportation to extracellular insoluble electron acceptors in sulfate-reducing bacteria (SRB) through a diffusion-based electron shuttle mechanism. Herein, in vivo electrochemistry shows that outer-membrane cytochromes (OMCs) directly mediated extracellular electron transfer (EET) in Desulfovibrio ferrophilus IS5. Anodic current production by IS5, coupled with lactate oxidation, was detected on indium-tin-doped oxide electrodes poised at +400 mV (vs. standard hydrogen electrode), which was the sole electron acceptor. Subsequent electrolyte replacement experiments with a fresh one showed that cells attached to the electrode contributed to 73% of current production by direct EET, while the electron shuttle mechanism may have contributed to the rest. Differential pulse voltammetry detected two redox species at E = −180 and 20 mV, with the former being most likely assignable to cell-surface cytochromes because nitric oxide decreased the peak current at −180 mV, as previously demonstrated with OMCs in iron-reducing bacteria. The EET onset potential at −200 mV further supports the notion that OMCs mediated EET in IS5, and that EET is thermodynamically favorable for reducing Fe(III) oxide. These results suggest that the direct EET mechanism regulates the reduction rate of insoluble substrates in SRB.

A coupled electrochemical process for schwertmannite recovery from acid mine drainage: Important roles of anodic reactive oxygen species and cathodic alkaline

The increasing need for sustainable acid mine drainage (AMD) treatment has spurred much attention to strategic development of resource recovery. Along this line, we envisage that a coupled electrochemical system involving anodic Fe(II) oxidation and cathodic alkaline production will facilitate in situ synthesis of schwertmannite from AMD. Multiple physicochemical studies showed the successful formation of electrochemistry-induced schwertmannite, with its surface structure and chemical composition closely related to the applied current. A low current (e.g., 50 mA) led to the formation of schwertmannite having a small specific surface area (SSA) of 122.8 m2 g−1 and containing small amounts of –OH groups (formula Fe8O8(OH)4.49(SO4)1.76), whereas a large current (e.g., 200 mA) led to schwertmannite high in SSA (169.5 m2 g−1) and amounts of –OH groups (formula Fe8O8(OH)5.16(SO4)1.42). Mechanistic studies revealed that the reactive oxygen species (ROS)-mediated pathway, rather than the direct oxidation pathway, plays a dominant role in accelerating Fe(II) oxidation, especially at high currents. The abundance of •OH in the bulk solution, along with the cathodic production of OH−, were the key to obtaining schwertmannite with desirable properties. It was also found to function as a powerful sorbent in removal of arsenic species from the aqueous phase.

A cost-effective H2S pollutant electro-transformation to hydrogen clean fuel and value-added semiconducting materials: A green alternative to Claus process

A straightforward strategy to resolve the H2S problem is its neutralization in alkaline media, followed by electrolysis of the obtained solution upon suitable electrodes. Herein, we report for the first time that via galvanostatic electrolysis of the resulting alkaline sulfide medium over copper electrodes, this harmful pollutant could be safely as well as cost-effectively transformed to hydrogen clean fuel and a value-added eco-friendly semiconducting material. The strong interaction of copper with bisulfide (the dominant species of the medium at pH 11) resulted in a significant decrease in the system impedance, accompanied by less electricity consumption during the process. A nano/micro-structured, mesoporous morphology was observed for the anodic product (surface area: 11.4 m2/g). Photoelectrochemical and diffuse reflectance as well as XRD, EDX, XPS and photoluminescence investigations revealed that the material synthesized upon the anode surface was a narrow bandgap (Eg=1.63eV) p-type semiconductor. In addition to the economic perspective of the proposed electrolysis process (3 ∼ 6 USD/kgH2), the underlying mechanism of simultaneous production of semiconductor (CuS) and H2 was thoroughly discussed.