Alkaline Electrolyte Solution Research Articles

N, P co-doped graphene enriched phosphorus as a highly efficient oxygen reduction catalyst

• N -doped first to promote the introduction of P into Gr at secondary heat treatment. • While doping N, high content P doping with 2.61 at% is realized in P N Gr. • P N Gr shows high specific surface area and abundant micro- and mesopores. • P N Gr displays excellent ORR and alkaline zinc-air battery discharge performance. • P N Gr exhibits wonderful stability and methanol resistance. Heteroatoms doped metal-free carbon catalysts are considered as promising alternatives to commercial Pt/C for oxygen reduction reaction (ORR). Here, we report a phosphorus-enriched nitrogen and phosphorus co-doped graphene catalyst (P N Gr) via a facile and economical two-step pyrolysis approach. Thanks to its outstanding properties, such as unique honeycomb-like morphology, high Brunauer-Emmett-Teller (BET) surface area (935 m 2 /g), and abundant of phosphorus content (2.61 at%), the obtained P N Gr exhibits a high ORR activity with a half-wave potential of 0.82 V and a limiting current density of −5.98 mA cm −2 in alkaline electrolyte solution. Notably, the zinc-air battery assembled with P N Gr as cathode catalyst also shows an excellent discharge performance and stability.

Adjusting electronic structure coupling of Fe–Ni2P (NiFeP-MOF) multilevel structure for ultra-activity and durable catalytic water oxidation

Efficient electrocatalyst for alkaline oxygen evolution reaction is the critical core to the wide application of metal-air energy storage and water electrolysis hydrogen energy. Therefore, appropriate design of highly active and stable non-noble metal oxygen evolution electrocatalyst with good electronic structure and multilevel structure is both a goal and a challenge. Here, we report a Fe–Ni2P electrocatalyst (NiFeP-MOF) with multilevel structure, which was obtained by anion exchange on the basis of Fe–Ni(OH)2 (NiFe-MOF) grown on nickel foam in situ by solvothermal method. As expected, Fe substitution regulates the Ni oxidation state in the NiFeP-MOF and realizes electronic structure coupling, showing a highly active and stable oxygen evolution reaction (OER) in alkaline electrolyte solution. Specifically, the NiFeP-MOF demonstrates an ultralow overpotentials (232 mV, 10 mA cm−2; 267 mV 100 mA cm−2), respectively, an extremely small Tafel slope (34 mV dec−1). Separately, the electrocatalyst shows an excellent cycle stability at 10 mA cm−2 for 12 h (43,200 s). More importantly, this work come up with an available policy for the preparation of excellent alkaline hydrolysis electrolysis catalysts and air cathodes with excellent performance.

Electrochemical Detection and Analysis of Various Current Responses of a Single Ag Nanoparticle Collision in an Alkaline Electrolyte Solution.

A single silver (Ag) nanoparticle (NP) collision was observed and analyzed in an alkaline solution using the electrocatalytic amplification (EA) method. Previously, the observation of a single Ag NP collision was only possible through limited methods based on a self-oxidation of Ag NPs or a blocking strategy. However, it is difficult to characterize the electrocatalytic activity of Ag NPs at a single NP level using a method based on the self-oxidation of Ag NPs. When using a blocking strategy, size analysis is difficult owing to the edge effect in the current signal. The fast oxidative dissolution of Ag NPs has been a problem for observing the staircase response of a single Ag NP collision signal using the EA method. In alkaline electrolyte conditions, Ag oxides are stable, and the oxidative dissolution of Ag NPs is sluggish. Therefore, in this study, the enhanced magnitude and frequency of the current response for single Ag NP collisions were obtained using the EA method in an alkaline electrolyte solution. The peak height and frequency of single Ag NP collisions were analyzed and compared with the theoretical estimation.

One A3B Porphyrin Structure-Three Successful Applications.

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A3B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by 1H- and 13C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039–6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon–steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A3B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = −10 mA/cm2 and a Tafel slope value of 205 mV/dec.

Hybridized bimetallic phosphides of Ni–Mo, Co–Mo, and Co–Ni in a single ultrathin-3D-nanosheets for efficient HER and OER in alkaline media

Highly efficient electrocatalysts based on non-noble and earth-abundant elements for overall water splitting are of great significance for sustainable energy conversion and storage. Herein, hybridization of three bimetallic phosphides, nickel-molybdenum (Ni–Mo), cobalt-molybdenum (Co–Mo), and cobalt-nickel (Co–Ni), in single ultrathin-3D-nanosheets on nickel foam (NMCP@NF) was carried out to fabricate an active and robust trimetallic metal-phosphide electrocatalyst for overall electrochemical water splitting. Simple hydrothermal synthesis followed by chemical vapor deposition-based phosphorization was used to fabricate the present catalyst. By using the optimum stoichiometric ratios of metals precursors, NMCP@NF nanosheets were achieved with the best electrical conductivity and high electrochemically active sites, resulting in high electrocatalytic activities with excellent kinetics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The NMCP@NF exhibited a low overpotential of 88 mV at 10 mA cm−2 for HER and a low overpotential of 250 mV at 10 mA cm−2 for OER. The NMCP@NF (+, -) device required a cell voltage of 1.52 V to reach a current density of 10 mA cm−2 in an alkaline electrolytic solution. The present study demonstrated that NMCP@NF as the best transition metal phosphide for overall water splitting.

Hard template derived N, S dual heteroatom doped ordered mesoporous carbon as an efficient electrocatalyst for oxygen reduction reaction

At present, a low-cost and efficient electrocatalyst is vital to conquering the sluggish oxygen reduction reaction (ORR) in fuel cells. In particular, N and S dual heteroatom doped mesoporous carbon (NSMC) catalysts are believed to be one of the best ORR catalyst options due to the distribution of nitrogen, sulfur sites. In this work, for NSMC synthesis we employed 2D Santa barbara amorphous (SBA-15) silica as support material and L-cysteine as N and S dual precursor. The optimal loading of NSMC-0.4, reveals the high concentration of defect sites (ID/IG = 0.99), pyridinic (21.41 at. %), graphitic-N (50.27 at. %), thiophene-S (77.16 at. %) sites on MC surface resulting in an improved ORR performance. The NSMC-0.4 showed more positive onset potential of 0.78 V vs. RHE, half-wave potential of 0.68 V, current density of 2.8 mA/cm2, peroxide production of 81%, followed by two-electron reduction process and lower Rct of 10 Ω/cm2 in an alkaline electrolyte solution. However, NSMC-0.6 demonstrated the higher amount of peroxide selectivity (150%) due to the presence of a large quantity of pyrrolic-N sites. In addition, our work provide an excellent guide for the synthesis and design of NSMC for efficient peroxide production via an electrochemical synthesis route.

Metal-free pristine halloysite nanotubes: Electrochemically active and stable oxygen evolution reaction

Halloysite nanotubes (HNT) are naturally occurring one-dimensional porous clay minerals and have a unique chemical structure of kaolinite. The presence of hydroxyl functional groups on the surface of HNT is more suitable for O2 evolution reaction (OER). The HNT based electrocatalyst coated on Ni foam substrate shows excellent water oxidation activity with an overpotential of 287 mV to reach a current density of 10 mA cm−2 and have excellent stability in alkaline electrolyte solution over 32 h without any decay. The adsorption of OH− species occurs on the surface of HNT from the alkaline electrolyte via one-electron transfer, the metal cation underwent repeated oxidation and reduction reactions during the OER. This result outperforms many of the transition metal-based electrocatalysts. This work provides a new platform to use naturally abundant clay minerals as an anode material in fuel cell applications.

Defect-rich engineering of Ni-incorporated tungsten oxides micro-flowers on carbon cloth: A binder-free electrode for highly efficient hydrogen evolution reaction

Hydrogen generated by electrocatalysis water splitting is a promising way to harvest clean energy. However, exploring the cheap and highly efficient electrocatalysts with Pt-like activity for hydrogen evolution reaction (HER) remains great challenges. Herein, we report hierarchical Ni-incorporated oxygen vacancies-rich tungsten oxides micro-flowers on 3D conductive carbon cloth support (denoted as Ni–W H2-550) as a binder-free electrode for high efficient hydrogen evolution. The binder-free 3D structure and the synergistic effect between Ni-incorporated and rich oxygen vacancies can regulate the electronic structure, facilitate the electron transfer, and enlarge the exposed active sites. The as-prepared Ni–W H2-550 exhibits a low overpotential of 25 mV at 10 mA cm−2 with robust stability in alkaline electrolyte solution over 20 h. This study opens up a concise strategy toward the preparation of the low-cost and highly efficient electrocatalyst for HER.

A New Photoelectrochemical Reactor with Special Photocathode Design for Hydrogen Production

Both electrodeposition and performance assessment of new photocathode design are carried out using cuprous oxide for solar hydrogen production. The maximum delivered light can be collected using the mesh dome design of the photocathode, and the light can also reach the farthest photocathode surfaces via the mesh shape. The stainless‐steel mesh dome electrode is coated with cuprous oxide using the electrodeposition method. This photocathode is examined in an alkaline electrolyte solution of potassium dioxide for hydrogen production. Two light angles are studied to explore the effects of the new photocathode design on the hydrogen yield rate and associated energy and exergy system efficiencies during the daytime, where the light angles change. The maximum hydrogen production rates are generated experimentally at 0.1 m KOH at the 45° tilt light, and vertical light positions are 5.13 and 5.58 μg s−1, respectively. Moreover, the highest exergy and energy system efficiencies are 0.82% and 1.18%, respectively, under vertical light, while they are 0.75% and 1.09% under tilted light conditions. The improvement of hydrogen production rates at tilted light can reach around 75.6% of the enhancement by vertical light due to the new photocathode design.

Development of α‐MnO2 Nanowire with Ni‐ and (Ni, Co)‐Cation Doping as an Efficient Bifunctional Oxygen Evolution and Oxygen Reduction Reaction Catalyst

AbstractManganese oxides (MnO2) with nanowire morphology materials are promising candidates for improving oxygen evolution and oxygen reduction reaction (OER/ORR) performance. In this work, we developed transition metal cation doping strategy into the α‐MnO2 tunnel structure to tune the Mn oxidation states and control the uniform nanowire morphology, crystalline structure to investigate the effect of doping over bifunctional activity. The single Ni2+ cation doping in α‐MnO2 with various loading concentrations resulted in 8Ni−MnO2 exhibiting remarkable OER and ORR activity owing to their excessive concentration of Mn3+ and Mn4+ octahedral sites respectively. Further, Co2+ cation doping in 8Ni−MnO2 leads to an enhanced synergistic effect that significantly improves the fraction of Mn3+ quantity which is confirmed by average oxidation state. For electrochemical OER performance, 8Co−8Ni−MnO2 exhibits a potential of 1.77 V, Tafel slope value of 68 mV dec−1 and lower charge transfer resistance and it is active in ORR with more positive onset potential of 0.90 V, half‐wave potential of 0.80 V, better current density (4.7 mA cm−2) and a four‐electron pathway. Moreover, bifunctional activity (ΔE=EOER@10 mA cm−2 – ORR@E1/2) of 8Co−8Ni−MnO2 demonstrated 0.97 V, indicates an excellent activity in alkaline electrolyte solution.

Multifunctional Carbon-Armored Ni Electrocatalyst for Hydrogen Evolution Under High Current Density in Alkaline Electrolyte Solution

Multifunctional Carbon-Armored Ni Electrocatalyst for Hydrogen Evolution Under High Current Density in Alkaline Electrolyte Solution

Exploration of Copper Oxide Nanoneedle Electrosynthesis Applied in the Degradation of Methylene Blue.

In this study, we report a low cost, fast and unexplored electrochemical synthesis strategy of copper oxide nanoneedles films as well as their morphological and chemical characterization. The nanostructured films were prepared using electrochemical anodization in alkaline electrolyte solutions of ethylene glycol, water and fluoride ions. The film morphology shows nanoneedle-shaped structures, with lengths up to 1–2 μm; meanwhile, high-resolution X-ray photoelectron spectroscopy (HRXPS) and spectroscopy Raman analyses indicate that a mixture of Cu(II) and Cu(I) oxides, or only Cu(I) oxide, is obtained as the percentage of water in the electrolyte solution decreases. A preliminary study was also carried out for the photocatalytic degradation of the methylene blue (MB) dye under irradiation with simulated sunlight in the presence of the nanoneedles obtained, presenting a maximum degradation value of 88% of MB and, thus, demonstrating the potential characteristics of the material investigated in the degradation of organic dyes.

Vanadium Copper Hydroxy Carbonate Hydrate Towards the Electrocatalytic Oxygen Evolution Reaction

Hydrogen with the highest energy density of 142 kJ/g has been considered as the green fuel to replace the non-renewable sources of energy in order to fulfil the increasing global energy demand. Electrocatalytic water splitting is one of the well-known processes to generate hydrogen gas, where oxygen evolution reaction (OER) occurring at the anode is the most sluggish part due to the involvement of multi-step electron transfer process. RuO2/IrO2 based electrodes are the best-known anode for such electrocatalytic cell. Due to the scarcity and high cost of such noble metals, it is urgent requirement to design non-noble metal based electrocatalytic material for OER. Recent advancements have demonstrated the utilization of vanadium-based and copper-containing materials as the most promising electrocatalyst for OER due to the strong synergic electronic and structural effects. In the present work, different ratios (1:2, 1:1 and 2:1) of vanadium copper hydroxy carbonate hydrates (VCHCH) were synthesized using hydrothermal and wet-chemical methods. The obtained materials were then deposited onto carbon-cloth substrate electrodes by drop casting and used as working electrode in a three-electrode cell setup consisting of a platinum-mesh as the counter electrode and Hg/HgO (1.0 M KOH) as the reference electrode in 1.0 M KOH, alkaline electrolytic solution. The electrochemical studies revealed that the inactive vanadium hydroxide became highly active towards the OER upon the addition of copper into the material. A current density of 10 mA/cm2 was achieved at the potential of 0.747 V, 0.768V and 0.760 V vs. Hg/HgO for the copper to vanadium ratios of 1:2, 1:1, and 2:1, respectively. The material also demonstrated a high stability with a consistent current density over 20 hours of experimental time. Figure 1

Facile synthesis of a copper oxide/molybdenum disulfide heterostructure for asymmetric supercapacitors of high specific energy

A unique p-n heterostructural CuO/MoS2 composite is synthesized by a facile hydrothermal method. The active edge-sites of two-dimensional MoS2 nanosheets provide ample surface area for firm attachment of urchin-shaped CuO particles without agglomeration during formation of the p-n heterostructure. The composition and morphology of the heterostructure are characterized by field-emission scanning electron microscopy, X-ray diffraction, Fourier - transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The synergism between CuO and MoS2 enhances electrochemical performance by increasing the number of sites available for redox reactions. Electrochemical measurements establish a specific capacitance of 268 F/g and a cyclic stability of 90.02 % in an alkaline electrolyte solution. An asymmetric supercapacitor fabricated with a CuO/MoS2 positive electrode and a biomass-derived activated carbon (BAC) negative electrode (CuO/MoS2//BAC) achieved a specific energy of 26.66 W h/kg at a specific power of 1599.6 W/kg.

Phosphorus substitution into Co3S4 nanoneedle arrays for efficient hydrogen evolution catalysis

Transition-metal based hybrids with excellent stability and activity are favorable candidates for hydrogen evolution reaction (HER). The development of typical Co3S4 has recently received considerable attention due to the multiple valences of the spinel-structured compound. However, the in-depth effect of the dopants on the HER performance of Co3S4 has not been systematically clarified. Here, we report a sequential synthesis of a spinel-structured cobalt phosphosulfate nanoneedle arrays grown on carbon cloth (namely, P-Co3S4/CC). Results indicate that P-Co3S4/CC exhibits high electrocatalytic performance for HER with a low overpotential of 65 mV to drive10 mA cm−2, a small Tafel slope of 76.6 mV per decade, and great long-term stability for 25 h at various current densities in alkaline electrolyte. The first-principle calculation result reveals that the phosphorous doping work at Co3S4 enhances the HER performance significantly because the tetrahedral Co2+ active sites nearest the P atoms more easily weaken the H–O bond to form intermediates. The experiment result characterization and theoretical calculations further show that the introduction of P atom not only offers more active sites but also improves the electrical conductivity in an alkaline electrolyte solution. Consequently, the identification of active species provides feasible guidance for the further design of high-performance spinel-structured catalysts.

Carbon-Supported Mo2C for Oxygen Reduction Reaction Electrocatalysis.

Molybdenum carbide (Mo2C)-based electrocatalysts were prepared using two different carbon supports, commercial carbon nanotubes (CNTs) and synthesised carbon xerogel (CXG), to be studied from the point of view of both capacitive and electrocatalytic properties. Cation type (K+ or Na+) in the alkaline electrolyte solution did not affect the rate of formation of the electrical double layer at a low scan rate of 10 mV s−1. Conversely, the different mobility of these cations through the electrolyte was found to be crucial for the rate of double-layer formation at higher scan rates. Molybdenum carbide supported on carbon xerogel (Mo2C/CXG) showed ca. 3 times higher double-layer capacity amounting to 75 mF cm−2 compared to molybdenum carbide supported on carbon nanotubes (Mo2C/CNT) with a value of 23 mF cm−2 due to having more than double the surface area size. The electrocatalytic properties of carbon-supported molybdenum carbides for the oxygen reduction reaction in alkaline media were evaluated using linear scan voltammetry with a rotating disk electrode. The studied materials demonstrated good electrocatalytic performance with Mo2C/CXG delivering higher current densities at more positive onset and half-wave potential. The number of electrons exchanged during oxygen reduction reaction (ORR) was calculated to be 3, suggesting a combination of four- and two-electron mechanism.

Polyethylene oxide-polypropylene oxide -polyethylene oxide derived porous carbon materials with different molecular weights as ORR catalyst in alkaline electrolytes

Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol−1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density，half-wave potential and initial potential are 5.23 mA cm−2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution.

Hydrophobic electrocatalyst for the enhanced activity of oxygen reduction reaction through controllable liquid/gas/solid interface

Slow gas consumption process has been considered as one of the main limiting factors to enhance the activity of oxygen reduction reaction (ORR). The superwettable materials can overcome the limitation of underliquid gas transport in electrocatalysis, however, most of the preparation process are complex and high cost. Herein, an electrocatalyst for ORR is synthesized by loading ZIF-67 on carbon black, then the hydrophobicity is bestowed on the catalyst and controlled by adjusting the amount of 1H,1H,2H,2H-perfluorodecyltriethoxysilane, aimed to preparing the carbon-based electrocatalyst with hydrophobic surface (Cal-CoZIF-XE2B/PFDS). Continuous and abundant cavitations on the catalyst surface ensure the rapid diffusion of oxygen to the three phase contact area of the reaction system. Compared with the unmodified catalyst, the hydrophobic catalyst has larger diffusion-limited current density (from 4.4 mA/cm2 of the original catalyst to 5.2 mA/cm2 of the modified catalyst) and higher half-wave potential (from 0.81 V of the original catalyst to 0.83 V of the modified catalyst). Furthermore, the as-prepared electrocatalysts which obtained with low cost and simple method, presenting durability and stability against alkaline and acidic electrolyte solutions and providing a general and reliable strategy for the study of ORR catalyst.

Three dimensional flower-like CuO/Co3O4/r-GO heterostructure for high-performance asymmetric supercapacitors

The supercapacitors have been widely used in the field of electronics appliances and automobiles, but its utility is limited by low energy density and poor specific capacitance. Energy density and specific capacitance of the supercapacitor is invariably determined by the electrode materials. Herein, a novel 3D flower-like CuO/Co3O4/r-GO heterostructure was synthesized by the hydrothermal method and used as an anode material for high-performance supercapacitors in an alkaline electrolyte solution. The as-prepared 3D flower-like CuO/Co3O4/r-GO heterostructure with high surface area provides vast interfacial contact area between electrode and electrolyte solution which offers a fast surface reaction kinetics and improved conductivity, thereby the remarkable electrochemical performance is achieved. The prepared CuO/Co3O4/r-GO heterostructure material shows an ultra-high specific capacitance of 1458 Fg-1 at a current density of 0.5 Ag-1, exceptional rate capability, and stable long- term cycling performance (97% retention after 10000 successive charge-discharge cycles at 5 Ag-1). In as-assembled asymmetric supercapacitor, CuO/Co3O4/r-GO heterostructure is an anode material and r-GO is a cathode material. The assembled device shows a high specific capacitance of 198 Fg-1 at 2 Ag-1, an ultra-high power density of 10510.30 W kg−1, and a high energy density of 34.20 Wh kg−1. Meanwhile, the ASC device exhibits excellent rate capability (97%) after 10000 successive charge-discharge cycles at 5 Ag-1 in the PVA-KOH gel electrolyte.

A study of the electrolyte composition influence on the structure and properties of MAO coatings formed on AMg6 alloy

The influence of electrolysis conditions at different electrolyte compositions on the phase formation and properties of coatings obtained by microarc oxidation (MAO) on an aluminum alloy AMg6 was studied. For electrolysis, three types of electrolytes were used: alkaline electrolyte ((KOH) solution in distilled water), silicate electrolyte (with different percentages of Na 2 SiO 3 component) and complex alkaline silicate electrolyte with liquid glass (1÷12 g/l Na 2 SiO 3 ) and potassium hydroxide (1÷6 g/l KOH). An analysis of the results showed that the choice of electrolyte type and conditions of the microarc oxidation process allows a wide variation in the phase-structural state, thickness and properties of the AMg6 aluminum alloy. The criterion for the expected phase-structural state of the coatings as a result of microarc oxidation is the completeness of the γ–Al 2 O 3 →α–Al 2 O 3 transformation process during coating formation. The use of an alkaline electrolyte does not allow achieving a high hardness of the coating due to the formation of the γ-Al 2 O 3 phase and the absence of thermodynamic conditions for the γ–Al 2 O 3 →α–Al 2 O 3 transition. When using a silicate electrolyte, it is possible to significantly increase the growth rate of the coating, but at the same time, the presence of a large specific Si concentration stimulates the formation of mullite and an amorphous-like phase. The use of a combined alkaline silicate electrolyte (with different percentages of KOH+Na 2 SiO 3 ) with a low content (6 g/l) of Na 2 SiO 3 in solution stimulates the formation of mullite. This is manifested to the greatest extent with the lowest content (1 g/l) of the KOH component. At a higher content (2 g/l) of the KOH component, the processes characteristic of an alkaline electrolyte become dominant. This leads to an incomplete transformation reaction and the formation of only the γ-Al 2 O 3 phase. The achievement of the thermodynamic conditions of the γ–Al 2 O 3 →α–Al 2 O 3 conversion became possible with an increase in the specific Na 2 SiO 3 content in the electrolyte solution to 12 g/l. In this case, MAO coatings were formed on the AMg6 alloy with the highest hardness of 1500 kg/mm 2 and high electric strength of 12 V/μm