Anodic Deposition Research Articles

Highly reversible Zn anode by guiding uniform Zn deposition through LiF protective layer

Deep-seated issues such as ineluctable dendrite deposition and parasitic reaction of Zn anode pose a major obstacle to the commercialization of aqueous zinc ion batteries (AZIBs). Herein, we proposed LiF as a solid-electrolyte interphase for highly reversible Zn anode. Combining experimental analyses and theoretical simulation calculations, the electronegative fluorine atoms could provide uniform zincophilic nucleation sites to regulate Zn deposition behavior. Additionally, a ZnF2 layer with outstanding Zn2+ conductive can be formed insitu thus further shielding bulk water molecules and expediting the Zn2+ transfer kinetics. Therefore, the LiF@Zn symmetric cells manifest long-cycling stability with 650 h at 1.0 mA/cm2 and 1.0 mAh/cm2 and 1000 h at 2.0 mA/cm2 and 1.0 mAh/cm2. Meanwhile, the rate performance of Zn//MnO2 and Zn//NH4V4O10 full cells are also enhanced by the LiF coating. This work provides a horizon for the design of artificial protective layer and promotes the large-scale practical development of AZIBs.

Porous Dielectric Structure and Response Speed of Moisture Sensors

Humidity sensors are typically made of alpha-alumina films as porous dielectric materials deposited through the anodic spark deposition (ASD) technique, a unique anodic oxidation method to deposit ceramic coatings on the exterior of metals. Close attention to the precise composition of electrolyte solution is crucial when mixing chemical compounds. Moreover, the ASD process, which happens during dielectric breakdown at the anode surface in an electrochemical cell, is clearly followed by visible sparking at the anode/electrolyte interface, leading to the formation of various ceramic coatings on metal substrates. Electrical breakdown happens over an anodized barrier layer, typically amorphous aluminum oxide, which has been produced on the metal anode. The local high temperature (>2000°C) produced by electrical sparks melts the amorphous aluminum oxide and converts it to alpha-aluminum oxide, forming the stable foundation for a reliable humidity sensor.In this study, we produced a variety number of small pores to investigate the response speed of moisture sensors. The ASD current can be adjusted to control the number of small pores. The smaller current gives a greater number of small pores. We focused on low-humidity sensors, often referred to as dew-point sensors. In fabrication of dew-point sensors, Scanning Electron Microscopy (SEM) was used to examine and determine the size of pores. Three different currents, 30 mA, 25 mA, and 10 mA, have been tried for comparative analysis of small pores existing within large pores. Two pores have been measured for current 10 mA, resulting in sizes of 47 nanometer (nm) and 71 nm, respectively. Similarly, three small pores for current 30 mA were measured with sizes of 32 nm, 42 nm, and 31 nm respectively. After the testing of low-humidity (dew-point) sensors, we found that the number of small pores does not significantly affect the response speed of the sensors.

Interfacial coordination effects for uniform and reversible zinc anode deposition

The instability resulting from side reactions including zinc dendrites and hydrogen evolution observed at the interface between the anode and electrolyte has impeded the progress of aqueous zinc-ion batteries (AZIBs). In this study, 1,5-naphthalenedisulfonic acid (NA) is introduced to guide homogeneous and reversible deposition behavior of Zn2+ based on metal-coordination chemistry. Theoretical calculations combined with experiments demonstrate that the strong coordination effect between S and Zn results in the adsorption of a NA layer on the anode surface, suppressing side reactions while facilitating the uniform deposition of Zn2+. By and large, the inclusion of NA extends the cycling stability to nearly 3600 h at a current density of 0.5 mA cm−2 (0.5 mAh cm−2), and it enables durable cycling for 200 h even at a high current density of 20 mA cm−2 (10 mAh cm−2). The Zn||VNNC full battery can be cycled stably for 700 cycles at 5 A g−1 at a low N/P ratio (2.58). The consequence caters a new perspective on the coordination effect at the interface for zinc anodes to achieve high reversibility in AZIBs and ZICs.

Soft carbon filled in expanded graphite layer pores for superior fast-charging lithium-ion batteries

The slow kinetics and lithium deposition of graphite anode are considered the key limitations of fast-charging lithium-ion batteries. Expanded graphite has shown tremendous potential for the improvement of rate performance due to its massive active sites released and lifted lithium storage platform. However, the risk of structural collapse caused by fast charging will reduce the cycling life of the expanded graphite anode. Herein, this study designed a stable structure of expanded graphite by filling its layer pores with pitch-derived soft carbon (EGC). The honeycomb-like EGC is a great fast-charging candidate material with rich active sites, enlarged ion transport channels, and efficient ion transport interfaces. As the experimental and simulation results, the EGC electrode demonstrated significantly fast lithium-ions storage kinetics and durable long cycle life, compared to commercial fast-charging graphite anode. Notably, the EGC//LiNi0.8Co0.1Mn0.1O2 full cell delivered a superior fast-charging and stability performance (near 20 min charging for 80 % State of Charge). The simple multifunctional modification strategy for graphite anode in this work provides a new approach for superior fast-charging lithium-ion batteries.

Highly stable planted MXene auxiliary layer for high-performance zinc anode deposition regulation

Aqueous zinc-ion batteries have good application prospects in large-scale energy storage, but severe dendrite behavior hinders their development. This article reports a method of planting MXene on the surface of zinc foil, that is, while mechanically polishing with a high-speed rotating wire brush, MXene solution is added dropwise, and MXene is anchored on the surface of the zinc foil with the help of a certain pressure. The MXene layer under this preparation method is stronger than the traditional self-assembled MXene layer. The MXene layer therefore acts as a physical barrier, protecting the underlying active zinc from damage. At the same time, the good hydrophilicity of the planted MXene layer reduces the concentration gradient of the interfacial electrolyte and redistributes the zinc ion flux. The unique electric field effect of MXene reduces the desolvation energy barrier, improves the transfer kinetics of Zn ions, and promotes the deposition of zinc ions in the (002) crystal plane. Experimental results show that the symmetrical battery prepared by this method can cycle stably for more than 1000 h at 0.8 mA cm−2, while its Zn\\\\Cu asymmetric battery exhibits cycle stability of more than 700 times at 0.5 mA cm−2. While maintaining a high Coulombic efficiency of over 99 %. Full cells assembled from zinc foil anodes and VO2 cathodes protected by a planted MXene layer also demonstrate higher capacity advantages. Therefore, this more stable MXene layer provides a direction for the practical application of zinc metal anodes.

Construction of an n-Type Fluorinated ZnO Interfacial Phase for a Stable Anode of Aqueous Zinc-Ion Batteries.

Aqueous rechargeable zinc-ion batteries have become an ideal solution for the next generation of energy storage systems due to their low cost and high safety. However, the uncontrollable zinc dendrites and harmful side reactions of metal zinc anodes hinder the further development of aqueous zinc-ion batteries. In this work, the artificial fluoride zinc oxide (F-ZnO) interface phase is integrated in situ on the surface of zinc foil. The F-ZnO interface phase significantly inhibits the side reactions on the surface of the zinc electrode by reducing the direct contact between the electrolyte and the surface of the zinc foil. In addition, F-ZnO modified by a small amount of F doping shows enhanced conductivity and electron transport capacity, avoiding the accumulation of high concentration Zn2+ on the anode surface, and ultimately promoting the efficient nucleation and orderly deposition of a zinc anode. The cycle life of the symmetrical cell based on F-ZnO is as high as 2600 cycles at an area current density of 4 mA cm-2, which is much better than that of a commercial pure Zn electrode. The modified F-ZnO@Zn anode truly achieves the purpose of prolonging the anode's life.

Enhanced green hydrogen production via CdS/Cu-doped TiO2 nanotubes: Advancements in photoanode performance

Cadmium Sulfide (CdS) deposited Copper (Cu) doped TiO2 nanotube hybrid photoanode (CdS/Cu-TNT) is developed via electrochemical anodization and subsequent electrochemical deposition for efficient green hydrogen production. Cu-doping of TiO2 Nanotube (TNT) is achieved in one-step anodization, which is more energy efficient than conventional arc melting. Results indicate that CdS/Cu-TNT photoanodes increased carrier density by 9 times and achieved a low bandgap of 2.46 eV which enhancing their suitability as photoanodes. Particle size distribution analysis has shown that Cu doping causes thicker nanotube walls with decreased surface area. CdS is coated over the Cu-doped TNT to enhance the photoelectrochemical properties further. The photocurrent of CdS-deposited TNT is 7.8 times higher than bare TNTs. Raman Spectral Mapping indicates the uniformity of CdS deposition and Cu doping. Photostability experiments reveal excellent performance and switching characteristics for Cu-doped, CdS-deposited, and CdS/Cu-TNT hybrid samples. The hybrid electrode with larger diameter nanotubes shows a 52.39 % increase in the Fill Factor of photocurrent response for CdS/Cu-TNT. Moreover, hydrogen production is significantly enhanced, with CdS/TNT demonstrating a 3.8-fold increase and CdS/Cu-TNT demonstrating a 4.1-fold increase. This research highlights the potential of Cu doping in TiO2 nanotubes for hydrogen generation, offering improvements over the limitations of TiO2 as a photoanode.

MnO2 with/without Ni doped films on carbon fibers by for enhancing compression and thermoelectric performances of cement

A microwave anodic deposition process was developed to prepare MnO2/Ni-doped MnO2 films on carbon fibersfor the fillers of cement composites (CFRC) to enhance both thermoelectric and compression performances simultaneously. The resulting CFRCs were designated as M-MnO2/CFRC and M-Ni-MnO2/CFRC, respectively. The results showed that the M-Ni-MnO2/CFRC exhibited the best thermoelectric performance at 313K, achieving a Seebeck coefficient of −873.9 μV/K, electrical and thermal conductivities of 3.42 S/m and 0.613 W/mK, respectively, and thus ZT and PF values of 1.69 × 10−3 and 3.42μW/(m·K2), respectively. The superior thermoelectric performance of the M-Ni-MnO2/CFRCs compared to that of the M-MnO2/CFRCs or the MnO2/CFRCs without microwave involvement in electrodeposition was attributed to the increased density of states at the Fermi level in MnO2 due to Ni doping, and the better interfacial scattering electron carrier effect. Surprisingly, the compression strength of the M-Ni-MnO2/CFRC reached 82.5 MPa, marking a 171.2 % increase, while the elongation reached 1.71 %, a 3.50 times increase compared to pure cement.

Self-regulating shielding layer induces (002) plane directional deposition of zinc metal anode

Rechargeable aqueous zinc batteries (AZIBs) are ideal for grid-scale energy storage due to their safety and economic characteristics. However, uncontrollable side reactions and dendrite growth severely affect the reversibility of zinc anodes. In the interfacial reaction, inducing smooth deposition of dominant planes is crucial for stabilizing the zinc anodes. Herein, we report a highly concentrated 1‑butyl‑3-methylimidazolium ion (BMIM+) modified electrolyte to improve the diffusion and deposition behavior of Zn2+. Thanks to the strong adsorption effect of BMIM+ at the zinc anode interface, the self-regulating shielding layer inhibits water-induced parasitic reactions. Under the action of BMIM+, Zn2+ has the lowest diffusion energy barrier towards the (002) plane, thus transforming the electrodeposition from a randomly stacked sheet to a dense deposited layer in the Zn(002) plane. The results showed that the symmetric cell composed of the modified electrolyte had a cycle life of 3200 h at 1 mA cm−2, and the average coulombic efficiency (CE) of the asymmetric cell was as high as 99.8 %. The full cell assembled with ZnxV2O5·nH2O still provided 86 % capacity retention at 2 A g−1 after 500 cycles. This electrolyte modification strategy provides a promising option for modulating the anode/electrolyte interface chemistry to achieve high-performance AZIBs.

Regulating Zn2+ Solvation Shell Through Charge‐Concentrated Anions for High Zn Plating/Stripping Coulombic Efficiency

AbstractThe plating/stripping efficiency of zinc (Zn) is directly related to the efficiency of zinc utilization and cycle stability of the battery, which is affected by factors such as the solvated water‐related hydrogen evolution reaction (HER), Zn corrosion, and dendrite formation. Therefore, creating a weak solvate shell for Zn2+ with reduced solvated water molecules can promote stable deposition and stripping of the zinc anode. In this work, a novel approach using the concentrated charge effect of anions is proposed to remove the solvated water and improve the efficiency of Zn plating/stripping. 3 mol kg−1 (3 m) ZnCl2, Zn(ClO4)2, and Zn(BF4)2 electrolytes are used as the representatives to investigate how anions regulate the solvent shell of zinc ion to achieve high Zn plating/stripping Coulombic efficiency (CE). Computational results show that Cl− has a more concentrated charge compared to ClO4− and BF4−, indicating a stronger interaction with Zn2+. This concentrated charge effect reduces the number of water molecules in Zn2+ solvation structures. Benefiting from weak solvent structure, the average coulomb efficiency, and cycling stability of the Zn─Cu asymmetric cell using ZnCl2 electrolyte is better. Additionally, the Zn‐NaV3O8 full cell of the ZnCl2 electrolyte exhibits good electrochemical performance.

Porous Dielectric Structure and Response Speed of Moisture Sensors

We made moisture sensors using α-Al2O3 films as porous dielectric materials deposited through the anodic spark deposition (ASD). In this study, a variety number of small pores has been studied to investigate the response speed of moisture sensors. Three different surface morphologies have been studied using scanning electron microscopy (SEM). Sample DM23 has the maximum number of small pores. Small pores are defined as pore size ranging from 40 nm to several hundred nm. Sample TA40 has the minimum number of small pores. Sample FW06 has the medium number of small pores. We found that the sensor made from dielectric material with the maximum number of small pores has the fastest response speed, and that from the minimum number of small pores has the slowest response speed either from high humidity to low humidity or from low humidity to high humidity.

Direct Electrodeposition of Electrically Conducting Ni3(HITP)2 MOF Nanostructures for Micro-Supercapacitor Integration.

Micro-supercapacitors emerge as an important electrical energy storage technology expected to play a critical role in the large-scale deployment of autonomous microdevices for health, sensing, monitoring, and other IoT applications. Electrochemical double-layer capacitive storage requires a combination of high surface area and high electronic conductivity, with these being attained only in porous or nanostructured carbons, and recently found also in conducting metal-organic frameworks (MOFs). However, techniques for conformal deposition at micro- and nanoscale of these materials are complex, costly, and hard to upscale. Herein, the study reports direct, one step non-sacrificial anodic electrochemical deposition of Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 - Ni3(HITP)2, a porous and electrically conducting MOF. Employing this strategy enables the growth of Ni3(HITP)2 films on a variety of 2D substrates as well as on 3D nanostructured substrates to form Ni3(HITP)2 nanotubes and Pt@ Ni3(HITP)2 core-shell nanowires. Based on the optimal electrodeposition protocols, Ni3(HITP)2 films interdigitated micro-supercapacitors are fabricated and tested as a proof of concept.

Electrophoretic deposition of ceramic coatings from modified suspensions of microsized powders of doped BaCeO3 and BaCeO3–BaZrO3 proton-conducting electrolytes

This work investigates the influence of molecular iodine introduced as a charging agent into the suspensions based on the BaCe0.8Sm0.19Cu0·01O3 (BCSCuO), BaCe0·5Zr0·3Y0.1Yb0.1O3-δ (BCZYYbO) and BaCe0.89Gd0.1Cu0·01O3-δ (BCGCuO) proton-conducting electrolytes at concentrations up to 1.0 g/L on their electrokinetic properties. The peculiarities of changes in zeta potential, pH, conductivity of the suspensions, the thickness and morphology of the coatings depending on the amount of iodine added are determined. It has been established that when the iodine concentration increases to 1 g/L, the electrical charge of the particles and the sign of the zeta potential undergo a reversal. Additionally, there is a natural decrease in the pH value towards the acidic side and a corresponding increase in the suspension conductivity. The research has demonstrated that in the suspension with a high iodine content (1 g/L), cathodic and anodic deposition can occur simultaneously under electrophoretic deposition (EPD) conditions at low voltage values (below 8 V). However, as the voltage increases, only cathodic deposition occurs. Therefore, the impact of altering the type of the EPD is threshold in nature relative to the magnitude of the EPD voltage. It has been shown that in order to practically implement EPD of ceramic coatings from modified suspensions of microsized powders of doped BaCeO3 and BaCeO3–BaZrO3 proton-conducting electrolytes, it is necessary to select a small amount of added iodine (0.1–0.2 g/L) to initiate a stable deposition process and to ensure continuity and uniformity of the coatings. This article discusses possible mechanisms of zeta potential inversion, electrophoretic mobility, and the EPD nature under conditions of high concentrations of iodide ions in the suspension bulk. The experiments have demonstrated the viability of the EPD process for the formation of a uniform BCSCuO coating (∼10 μm) on a supporting NiO–BCSCuO anode substrate using an iodine-modified suspension. This coating was subsequently sintered into a dense ceramic film at 1450 °C. In addition to the fundamental significance, the study results have implications for the practical use to improve and simplify the thin-film SOFC technology.

Electrochemical cobalt oxidation in chloride media

The green transition, despite recent advances in cobalt-free battery technologies, is still highly dependent on the availability of critical cobalt-based materials. Consequently, there has been increasing interest towards the development of new methods that maximize critical metals recovery from industrial hydrometallurgical solutions. In the current study, direct anodic oxidation of cobalt species from cobalt chloride solutions was studied as one alternative future strategy for cobalt recovery. Electrochemical methods were used (cyclic voltammetry, potentiostatic anodic deposition) and the effect of pH, temperature, and the concentration of cobalt and chloride ions on cobalt precipitation were investigated. The increase of pH and temperature was shown to stabilize the electrochemical oxidation of cobalt, while a decrease in cobalt concentration had a negative effect on precipitation. Scanning Electron Microscope, Atomic Force Microscopy and X-ray Photoelectron Spectroscopy were exploited to evaluate the morphology, structure, and composition of obtained anodic product. Calculated for potentiostatic anodic deposition (at highest studied potential of 1300 mV vs. Ag/AgCl) nucleation mechanism shows that the rate of nucleation for oxygen-cobalt species is faster than the subsequent growth rate of nuclei (instantaneous mechanism). XPS results confirmed that mixed Co3O4/Co(OH)2/CoOOH precipitate could be obtained by optimized anodic potentiostatic deposition in the range from 900 to 1150 mV and pH from 3 to 6 at 60 °C.

ReS2-MoS2 heterojunction nanotube FET with superlattice structures for ultrasensitive detection of miRNA

Ultrasensitive detection of cancer biomarkers holds immense importance in facilitating the early diagnosis and treatment of cancer. Compared to conventional detection techniques, field-effect transistor (FET) biosensors have demonstrated substantial potential in achieving sensitive detection of cancer biomarkers. However, the ultrasensitive FET still remains great challenges due to the limited electron transport capacity and sensitivity of channel materials. Herein, we employed rhenium disulfide-molybdenum disulfide nanotube (ReS2-MoS2 NT) featuring superlattice structures as channel materials in FET biosensors for the highly sensitive detection of cancer biomarker miRNA-21. More concretely, ReS2-MoS2 NT featuring superlattice structures was synthesized using the anodic aluminum oxide (AAO) template sacrifice method and atomic layer deposition (ALD) method. The electrical properties of single ReS2-MoS2 NT FET were regulated by adjusting the total layers and number of heterojunction interfaces, and the optimal number of heterojunction interfaces of 7 was obtained. Finally, FET biosensors utilizing the network ReS2-MoS2 NT as the channel materials were fabricated and exhibited remarkable sensitivity in detecting miRNA-21 under an external light source. The linear range for detection spanned from 10 aM to 1 nM, with an exceptionally low detection limit of 2.1 aM. This study holds promise for replacing current channel materials and surpassing the detection threshold of cancer biomarkers in the future.

Modulation of Interfacial Characteristics of Copper Electrode by Electrodeposited Cu@Ti for High-Performance Anode-Free Zinc Ion Batteries.

Preparation of the NC-Cu@Ti electrode involved electrochemical deposition of nanocrystalline copper on the surface of titanium foil using a constant potential method, intended for high stability anode-free zinc ion battery (ZIB) anode material applications. This paper examines the effect of Cu2+ concentration in the electrodeposition solution on the structure and morphology of copper crystals on the NC-Cu@Ti electrode surface. The study also assesses how the interfacial properties of the NC-Cu@Ti electrode affect the process of anodic zinc deposition without anodic ZIBs. Our data suggest that with a voltage setting of -0.95 V and a copper ion concentration of 0.5 M in the solution, the deposition rate of copper crystals on the NC-Cu@Ti-0.5 electrode remains consistent. The resultant crystal phase surface appears smooth with a fine grain size. The NC-Cu@Ti-0.5 electrodes have increased hydrogen potentials and superior corrosion resistance; noting zinc nucleation sites at a mere 21.4 mV, it can provide stable electrochemical conditions for the zinc deposition interface of ZIBs and accelerate the process of zinc desolvation and nucleation. The constructed Zn//NC-Cu@Ti-0.5 asymmetric cell displays swift zinc deposition/stripping kinetics, elevated Coulombic efficiency, and prolonged stability (maintaining nearly 99% after 200 cycles). This performance significantly extends the service life relative to the Zn//Zn symmetric cell, which operates stably for 400 h at 1 mA/cm2. Moreover, the NC-Cu@Ti-0.5//MnO2 ZIBs offer enhanced conductivity and magnification performance to the pure zinc anode ZIBs. This study presents a novel approach for the low-cost and rapid preparation of anode materials for high-performance free-anode ZIBs.

Direct methanol oxygen-ion conducting solid oxide fuel cell with an integrated in-situ cracking reactor

Methanol, as an indirect hydrogen storage medium rich in hydrogen, is considered an ideal fuel for fuel cells. Oxygen-ion conducting solid oxide fuel cells (O-SOFCs) powered by methanol are renowned for their high energy conversion efficiency and minimal environmental impact, offering broad application prospects. However, challenges to their stable power generation arise from the rate of hydrogen production through methanol decomposition at the anode and carbon deposition on nickel-based anodes. To address these issues, this study explores the optimal operating temperature and concentration of methanol as an O-SOFCs fuel, while also developing a novel cell design. In this design, an in-situ cracking reactor for internal conversion of methanol is constructed by loading Ru-GDC high-efficiency nanofiber catalysts on dendritic anode microchannels, significantly enhancing the cell's power generation performance. Experimental results demonstrate that at 800 °C and a 30 % methanol concentration, the system increases the maximum power density (MPD) from 0.622 W cm−2 to 0.893 W cm−2, exhibiting a 43.57 % increase in power density and a 13.03 % improvement in methanol utilization. Additionally, the system effectively mitigates carbon deposition and nickel anode deactivation, thereby enhancing the cell's operational stability.

Morphology and Structure of TiO2 Nanotube/Carbon Nanostructure Coatings on Titanium Surfaces for Potential Biomedical Application.

Titanium is the most used material for implant production. To increase its biocompatibility, continuous research on new coatings has been performed by the scientific community. The aim of the present paper is to prepare new coatings on the surfaces of the pure Ti Grade 2 and the Ti6Al4V alloy. Three types of coatings were achieved by applying anodization and chemical vapor deposition (CVD) methods: TiO2 nanotubes (TNTs) were formed by anodization, carbon nanotubes (CNTs) were obtained through a metal-catalyst-free CVD process, and a bilayer coating (TiO2 nanotubes/carbon nanostructures) was prepared via successive anodization and CVD processes. The morphology and structure of the newly developed coatings were characterized using SEM, EDX, AFM, XRD, and Raman spectroscopy. It was found that after anodization, the morphology of the TiO2 layer on pure Ti consisted of a "sponge-like" structure, nanotubes, and nano-rods, while the TNTs layer on the Ti alloy comprised mainly nanotubes. The bilayer coatings on both materials demonstrated different morphologies: the pure Ti metal was covered by a layer of nanotubular and nano-rod TiO2 structures, followed by a dense carbon layer decorated with carbon nanoflakes, and on the Ti alloy, first, a TNTs layer was formed, and then carbon nano-rods were deposited using the CVD method.

Site-specific metal-support interaction to switch the activity of Ir single atoms for oxygen evolution reaction

The metal-support interactions (MSI) could greatly determine the electronic properties of single-atom catalysts, thus affecting the catalytic performance. However, the typical approach to regulating MSI usually suffers from interference of the variation of supports or sacrificing the stability of catalysts. Here, we effectively regulate the site-specific MSI of Ir single atoms anchored on Ni layered double hydroxide through an electrochemical deposition strategy. Cathodic deposition drives Ir atoms to locate at three-fold facial center cubic hollow sites with strong MSI, while anodic deposition drives Ir atoms to deposit onto oxygen vacancy sites with weak MSI. The mass activity and intrinsic activity of Ir single-atom catalysts with strong MSI towards oxygen evolution reaction are 19.5 and 5.2 times that with weak MSI, respectively. Mechanism study reveals that the strong MSI between Ir atoms and the support stimulates the activity of Ir sites by inducing the switch of active sites from Ni sites to Ir sites and optimizes the adsorption strength of intermediates, thereby enhancing the activity.

The role of electrical current mode in calcium carbonate deposition on conductive carbon nanofiber–epoxy coating

AbstractCalcium carbonate is one of the most common scaling minerals. In this paper we have used different electrical current modes (direct current [DC], pulsed DC, and alternating current [AC]) to control the amount, morphology, and distribution of calcium carbonate deposit on electroconductive epoxy/carbon nanofiber (CNF) coating. The effect of different current modes on surface scaling was visualized using scanning electron microscopy. It has been shown that both AC and DC anodic polarization limited scale deposition on epoxy/CNF coated surfaces, although the mechanisms of scale inhibition during AC and DC polarization were different. DC polarization of the coating at +2 V resulted in the smallest scale buildup without leading to coating degradation, while DC polarization at potentials as high as +5 V caused the coating to degrade. Interestingly, application of pulsed DC with high pulse frequency (50 Hz) inhibited the degradation. The type of current applied affected also the morphology of the precipitate at the cathode. The results presented in this work show, for the first time, how different modes of electrical current applied to electroconductive composite coatings can be used to control the morphology and distribution of calcium carbonate scale, and how the organic coating degradation at high polarization potentials can be avoided.