Electrodeposition Of Metals Research Articles

A Review of External Field-Enhanced Metal Electrodeposition: Mechanism and Applications

A Review of External Field-Enhanced Metal Electrodeposition: Mechanism and Applications

Mechanistic Understanding of Long Duration Fast Charge Aqueous Zinc Batteries Using Physically Adsorbed Oligomers as Interphases.

Polymers have been used as additives in the liquid electrolytes typically used for secondary batteries that utilize metals as anode. Such additives are conventionally argued to improve long-term anode performance by suppressing morphological and hydrodynamic instabilities thought to be responsible for out-of-plane and dendritic metal deposition during battery charging. More recent studies have reported that the polymer additives provide even more fundamental mechanisms for stabilizing metal electrodeposition through their ability to regulate metal electrodeposit crystallography and, thereby, morphology. Few studies explore how polymers carried in a liquid electrolyte achieve these functions, and fewer still provide rules for choosing among the various polymer types, the additive polymer molecular weight (Mw), and concentration in the electrolyte. Here, we investigate how these generally easy-to-control variables influence electrochemical interphase formation inside battery cells and their impact on the morphology and reversibility of Zn electrodes in aqueous electrolytes. We focus on aqueous Zn-iodine electrochemical cells containing linear polyethylene glycol (PEG) chains as additives and find that in electrolytes where the polymer concentration is maintained in the dilute solution regime there is an optimum polymer molecular weight (Mw ≈ 1000 Da), above which beneficial effects of polymers on Zn electrode reversibility and Zn-I2 battery lifetime are progressively lost. By means of optical ellipsometry and theoretical calculations, we show that the optimal Mw is associated with saturation of the thickness of a physiosorbed PEG coating on the Zn metal electrode. Electron microscopy and X-ray photoelectron spectroscopy analysis of Zn electrodeposits formed in such electrolytes reveal that the physiosorbed polymer coating has two primary effects─it regulates the deposit morphology and suppresses parasitic reactions between the electrode and electrolyte components. The parasitic reactions produce species like ZnO, which are known to passivate the Zn electrode and promote nonuniform deposition. Galvanostatic cycling measurements in aqueous Zn-I2 cells containing the PEG additives at the optimal Mw show that the cells maintain very high Coulombic efficiencies (≥99%) at current densities as high as 50 mA/cm2─close to the maximum values permissible across the Celgard separator membranes used in our studies.

Electrochemical Nucleation and Growth Mechanism of Metals

AbstractThis review provides a detailed analysis of the current transition observed in the field of electrodeposition of metals. Special emphasis is placed on the mechanism initiated by nucleation followed by diffusion‐controlled growth. The study highlights recent advances, relevant theoretical models, and practical implications of this process. Concrete examples are also discussed to illustrate the application of this method in various industrial and scientific contexts. These promising advances open new perspectives for the optimization of electrodeposition processes, paving the way for innovative applications in various technological sectors.

SEI Formation and Lithium-Ion Electrodeposition Dynamics in Lithium Metal Batteries via First-Principles Kinetic Monte Carlo Modeling.

The stabilization and enhanced performance of lithium metal batteries (LMBs) depend on the formation and evolution of the Solid Electrolyte Interphase (SEI) layer as a critical component for regulating the Li metal electrodeposition processes. This study employs a first-principles kinetic Monte Carlo (kMC) model to simulate the SEI formation and Li+ electrodeposition processes on a lithium metal anode, integrating both the electrochemical electrolyte reduction reactions and the diffusion events giving place to the SEI aggregation processes during battery charge and discharge processes. The model replicates the competitive interactions between organic and inorganic SEI components, emphasizing the influence of the cycling regime. Results indicate that grain boundaries within the SEI facilitate faster lithium-ion transport compared to crystalline regions, crucial for improving the performance and stability of LMBs. The findings underscore the importance of dynamic SEI modeling for further development of next-generation high-energy-density batteries.

Exploring the Impact of In Situ-Formed Solid-Electrolyte Interphase on the Cycling Performance of Aluminum Metal Anodes.

Unwanted processes in metal anode batteries, e.g., non-uniform metal electrodeposition, electrolyte decomposition, and/or short-circuiting, are not fully captured by the electrolyte bulk solvation structure but rather defined by the electrode-electrolyte interface and its changes induced by cycling conditions. Specifically, for aluminum-ion batteries (AIBs), the role of the solid-electrolyte interphase (SEI) on the Al0 electrodeposition mechanism and associated changes during resting or cycling remain unclear. Here, we investigated the current-dependent changes at the electrified aluminum anode/ionic liquid electrolyte interface to reveal the conditions of the SEI formation leading to irreversible cycling in the AIBs. We identified that the mechanism of anode failure depends on the nature of the counter electrode, where the areal capacity and cycling current for Al0 electrodeposition dictates the number of successful cycles. Notwithstanding the differences behind unstable aluminum anode cycling in symmetrical cells and AIBs, the uniform removal of electrochemically inactive SEI components, e.g., oxide-rich or solvent-derived organic-rich interphases, leads to more efficient cycling behavior. These understandings raise the importance of using specific conditioning protocols for efficient cycling of the aluminum anode in conjugation with different cathode materials.

In-situ realtime study of zinc selenide nanoparticles sustained by polypyrrole in alkaline water oxidation

Interest in metal electrodeposition for synthesizing customized nanomaterials has resurged, particularly for applications such as sensors and fuel cells. The present study involved the synthesis of ZnSe nanoparticles (via hydrothermal method) while polypyrrole and novel composite Ppy@ZnSePpy@Ppy (via sequential electrodeposition technique) on a glassy carbon (GC) electrode and their physiochemical, electrochemical, and operando spectro-electrochemical characterizations towards oxygen evolution reaction (OER). Results indicated that ZnSe nanoparticles are well embedded within the Ppy layers and during OER the composite electrocatalyst approached 398 mV at 10 mA cm−2 and exhibited Tafel value (b ∼ 75 mV dec−1) with ECSA (0.03) which shows better results than other two. In addition, the operando spectro-electrochemical spectra of the composite revealed the significant generation of active intermediate oxygen species of selenium and Zn2+. The important feature of the current work is the disclosure of Se's questionable role and species involved in OER found to be Se4+.

Initial stages of silver electrodeposition on a model Pt(111) single-crystal substrate from ethaline

Deep eutectic solvents (DES) are a new class of solvents with unique properties that are very promising media for the electroplating of metals and alloys. Knowledge about the regularities of metal electrodeposition is noticeably promoted by studies on model single crystal electrodes with a known well-ordered surface structure. In this work, we investigate the regularities of under- and overpotential deposition (upd and opd, respectively) of silver from a silver chloride solution in ethaline on a Pt(111) single crystal surface. For a better understanding of the occurring processes, we employ a complex approach involving electrochemical and in situ and ex situ microscopic techniques. We show that the process of gradual surface poisoning is observed on Pt(111) in the potential range in which no massive solvent degradation is yet observed. We also observe that the extent of this process largely depends on the employed potential of contact between the electrode and the solution and the studied potential range.The presence of Ag upd on Pt(111) in ethaline is demonstrated using voltammetric and in situ STM data. The available results and charge analysis are used to compare the Ag upd processes in ethaline and in aqueous solutions. We discuss the number of Ag adlayers on Pt(111), the effect of the potential of initial contact of the electrode with the solution and cycling history, and the possibility of anion upd and formation of coadsorbate between Ag adatoms and upd chloride anions (chlorine adatoms). We also demonstrate that upd Ag is not completely desorbed until high anodic potentials, where it seems to catalyze the solvent oxidation. Phase deposition of silver from ethaline on Pt(111) starts at almost zero overpotentials, which is probably related to the presence of the already deposited Ag adlayer. Even at very low overpotentials the deposit includes both large planar 2D crystallites and 3D crystallites formed on the surface defects and at the edges of the flat deposit islands. As the overpotential grows, the epitaxiality is gradually lost; the deposit becomes unshaped and the amount of 3D crystallites and their height increase.

Is the oxygen plasma cleaning technique indicated for any electrochemical purpose?: The case of FTO electrodes

Fluorine-doped tin oxide (FTO) is among the most used transparent conductive oxides (TCOs) in phototovoltaic devices such as photoelectrochemical and solar cells. Preparation of films on these TCOs can be achieved by several deposition techniques including electrodeposition. Among the several cleaning and activation procedures before a thin film deposition there is the oxygen plasma treatment, which has been successfully applied on several kind of substrate materials. Surprisingly, the use of this step on TCOs previously to the electrodeposition of a film is not a usual practice. Here we present a detailed study on the consequences of oxygen plasma process over FTO electrodes that are subsequently employed in several electrochemical reactions of practical importance. Open circuit potential (OCP) measurements from oxygen plasma treated FTO have proven the resorption of ions and/or solvent molecules in aqueous electrolyte following a pseudo-second order kinetic. Electrochemical reactions were quite sensible to the oxygen plasma treatment, even under mild conditions. In all cases FTO become deactivated for such electrochemical processes independently of the plasma set up employed except for metal electrodeposition. Partial recovering of the electrochemical response of FTO in the ferri/ferro system after annealing at 450 °C explains why oxygen plasma process is worthy only for other deposition techniques such as spray pyrolysis where similar temperatures are employed. Electrochemical Impedance Spectroscopy (EIS) analysis revealed a decrease of the majority carrier density (ND). This is mainly attributed to the oxyanion implantation on oxygen vacancies sites during the plasma process thus explaining the loss of activation of FTO. Energy level diagrams reveal the decrease of degeneracy of FTO towards an n-type semiconducting SnO2 film which is also supported by ultraviolet photoelectron spectroscopy (UPS). A band gap energy dependence with the plasma conditions allowed to check the filling of oxygen vacancies on the FTO surface without discard the loss of fluorine. Anodic polarization in acid media proved the impossibility of oxygen vacancies restitution, being the dominating process the partial etching of FTO.

Incorporation of Ag in Co9S8-Ni3S2 for Predominantly Enhanced Electrocatalytic Activities for Oxygen Evolution Reaction: A Combined Experimental and DFT Study.

Electrodeposition of abundant metals to fabricate efficient and durable electrodes indicate a viable role in advancing renewable electrochemical energy tools. Herein, we deposit Co9S8-Ag-Ni3S2@NF on nickel foam (NF) to produce Co9S8-Ag-Ni3S2@NF as a exceedingly proficient electrode for oxygen evolution reaction (OER). The electrochemical investigation verifies that the Co9S8-Ag-Ni3S2@NF electrode reveals better electrocatalytic activity to OER because of its nanoflowers' open-pore morphology, reduced overpotential (η10=125 mV), smaller charge transfer resistance, long-term stability, and a synergistic effect between various components, which allows the reactants to be more easily absorbed and subsequently converted into gaseous products during the water electrolysis route. Density functional theory (DFT) calculation as well reveals the introduction of Ag (222) surface into the Co9S8 (440)-Ni3S2 (120) structure increases the electronic density of states (DOS) per unit cell of a system and increases the electrocatalytic activity of OER by considerably lowering the energy barriers of its intermediates. This study provides the innovation of employing trimetallic nanomaterials immobilized on a conductive, continuous porous three-dimensional network formed on a nickel foam (NF) substrate as a highly proficient catalyst for OER.

The Deposition of Lead on a Pt(100) Electrode and the Effects on the Oxidation of Formic Acid

The electrodeposition of foreign metals on a platinum (Pt) electrode can be used to alter the electrochemical properties of the modified electrode. The current study employed in situ scanning tunneling microscopy (STM) to characterize the spatial structures of a monolayer and multilayer lead (Pb) electrodeposited on an ordered Pt(100) electrode in 0.1 M perchloric acid (HClO4) with and without formic acid under potential control. The Pt(100) bead crystal used in this study was pretreated by a modified annealing and quenching method, producing a long-range ordered, unreconstructed (1 × 1) surface. The underpotential deposition (UPD) of Pb on the Pt(100) electrode resulted in a pair of sharp and reversible peak at 0.5 V (vs. Ag/AgCl), prior to the bulk deposition at E < -0.45 V in 0.1 M HClO4 + 1 mM Pb(ClO4)2. Cyclic potential sweeping in the UPD regimes resulted in a stable voltammogram, but bulk Pb deposition led to varying morphologies of the profiles. Atomic resolution STM images were obtained to reveal a well-ordered Pt(100)-(√2 × √2)R45°-Pb structure and elongated rows of Pb aggregates and local (√2 × 2√2) R45° in the initial and final stages of Pb UPD, respectively. Bulk Pb deposition at E < -0.5 V led to a crystalline Pb film, but a roughened Pt(100) surface was imaged after the Pb deposit was anodically stripped. The activity of the Pt(100) electrode toward formic acid oxidation was nearly tripled after being modified with a sub-monolayer of Pb, and increased by another 20 % when it was loaded with multilayer Pb.

Design of a dynamically switchable metamaterial solar heating and daytime radiative cooling device based on reversible metal electrodeposition

Abstract The combination of daytime radiative cooling and solar heating can regulate the temperature of buildings in all seasons, which is vital to achieving energy savings. However, achieving a dynamic and efficient switch between radiative cooling and solar heating states is still challenging. The reversible metal electrodeposition is a promising electrochromic (EC) technology that can dynamically manipulate the visible and infrared spectrum by depositing a nanoscale metal layer. By combining it with a delicate nanostructure design, reconfigurable daytime radiative cooling and solar heating states can be achieved. In this work, a metamaterial EC device capable of efficiently switching between high solar reflectance (91.73%) and high solar absorptance (95.41%) via reversible silver layer electrodeposition has been developed. This device consists of a top layer, which is a visible transparent electrode of indium tin oxide covered with an ultrathin platinum film, an electrolyte in the middle, and a metamaterial absorber based on a metal/dielectric multilayered structure at the bottom. Afterward, we analyze the spectrum of each part of the device and carry out a parametric study on the practical performance with different ambient temperatures and convective heat transfer coefficients. The average solar reflectance of the device in the radiative cooling state is 93.41% within the range of 0.3–2.5 μm. In the solar heating mode, the average solar absorptance of the device reaches 95.46%. Numerical simulations show that the device in the cooling mode achieves a temperature drop of 5 °C–9.8 °C and an average cooling power of 140.8 W m − 2 . The device in heating mode achieves a maximum temperature rise of 45 °C and a maximum heating power of 700 W m − 2 . This work provides a feasible design for solar heating and daytime radiative cooling switching devices, which is promising in applications like energy-saving buildings, wearable devices, electric vehicles and other outdoors facilities.

Lithium-Ion Battery Recycling: Ternary Deep Eutectic Solvents Enable Efficient and Selective Electrochemical Recovery of Critical Component Metals

The growing demand for lithium-ion batteries (LIBs) in electric vehicles and energy storage systems has led to a rise in LIB waste. Efficient metal recovery from LIB waste is critical to meet the growing demand sustainably. However, traditional recycling methods, such as pyrometallurgy and hydrometallurgy, have limitations regarding energy consumption, efficiency, and environmental impact. In this work, we address these challenges by exploring the potential of Deep Eutectic Solvents (DESes) as an alternative. DESes are compounds formed by mixing hydrogen bond donors and acceptors and exhibit a high capability for metal dissolution. DES has a wide electrochemical stability window (1-2 V vs Ag), making it ideal for electrodeposition. While DES holds promise for sustainable LIB recycling, current applications are hindered by high leaching temperatures (140-220°C) and prolonged durations, extending even to days.In this study, we investigate the physical properties of a novel ternary DES and assess its leaching capabilities alongside electrodeposition studies. The leaching efficiency (LE) of metals using ternary DES is compared to the binary DES, composed of choline chloride and ethylene glycol (1:2 ChCl: EG). For the same leaching conditions (900C, 24 hr), the leaching efficiency (LE) of metals using binary DES, is 20%, whereas the LE of metals from ternary DES is nearly 100%. We optimized the leaching conditions and investigated the leaching kinetics. The electrochemical properties of the tailored, ternary DES are explored, revealing an electrochemical window of 2-3 V vs Ag. We analyze current density–time transients using the Scharifker–Hills model for instantaneous and progressive nucleation to study the early nucleation and growth mechanism of electrodeposition. Furthermore, we perform potentiostatic electrodeposition of metals from the leach liquor on different substrates, such as copper sheet and carbon at various constant potentials (-0.7 V to -1 V vs Ag). The effect of applied potential, stability of working and counter electrodes, and growth mechanism of deposited metals are studied. The electrodeposited metals are characterized using scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Our findings indicate that the proposed ternary DES holds significant promise for efficient and environmentally friendly metal recovery from LIB waste, paving the way for advancements in sustainable battery recycling technologies. Figure 1

(Invited) Intermetallics Based on Sodium Chalcogenides Promote Stable Electrodeposition – Electrodissolution of Sodium Metal Anodes

Sodiophilic micro-composite films of sodium-chalcogenide intermetallics (Na2Te and Na2S) and Cu particles are fabricated onto commercial copper foam current collectors (Na2Te@CF and Na2S@CF). For the first time a controllable capacity thermal infusion process is demonstrated. Enhanced wetting by the metal electrodeposition leads to state-of-the-art electrochemical performance. For example, Na2Te@CF-based half-cells demonstrate stable cycling at 6 mA cm-2 and 6 mAh cm-2, corresponding to 54 μm of Na electrodeposited/electrodissolved by geometric area. Sodium metal battery (SMB, NMB) cells with Na3V2(PO4)3 (NVP) cathodes are stable at 30C (7 mA cm-2) and for 10,000 cycles at 5C and 10C. Cross-sectional cryogenic focused ion beam (cryo-FIB) microscopy details deposited and remnant dissolved microstructures. Sodium metal deposited onto Na2Te@CF is dense, smooth, and free of dendrites or pores. On unmodified copper foam, sodium grows in a filament-like manner, not requiring cycling to achieve this geometry. Substrate-metal interaction critically affects the metal-electrolyte interface, namely the thickness and morphology of the solid electrolyte interphase (SEI). Density functional theory (DFT) and mesoscale simulations provide insight into support-adatom energetics, nucleation response, and early-stage morphological evolution. On Na2Te sodium atomic dispersion is thermodynamically more stable than isolated clusters, leading to conformal adatom coverage of the surface.

Stable Anode-Free All-Solid-State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector

Stable anode-free all-solid-state battery (AF-ASSB) with sulfide-based solid-electrolyte (SE) (argyrodite Li6PS5Cl, LPSCl) is achieved by tuning wetting of lithium metal on “empty” copper current-collector. Lithiophilic 1 μm Li2Te is synthesized by exposing the collector to tellurium vapor, followed by in-situ Li activation during the first charge. The Li2Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous plating experiments using half-cells (1 mA cm-2), the accumulated thickness of electrodeposited Li on Li2Te-Cu is more than 70 μm, which is the thickness of Li foil counter-electrode. Full AF-ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryo-FIB sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector-SE interface. Electrodissolution is uniform and complete, with Li2Te remaining structurally stable and adherent. By contrast, unmodified Cu current-collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive “dead metal”, dendrites that extend into SE, and thick non-uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory and mesoscale calculations provide complementary insight regarding nucleation-growth behavior. Unlike for conventional liquid-electrolyte metal batteries, the role of current collector/support lithiophilicy has not been explored for emerging AF-ASSBs.

Research on the Use of Low-Selenium Additives in the Electrodeposition of Manganese Metal and Co-production of Electrolytic Manganese

Research on the Use of Low-Selenium Additives in the Electrodeposition of Manganese Metal and Co-production of Electrolytic Manganese

Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries.

Manipulating the crystallographic orientation of zinc (Zn) metal to expose more (002) planes is promising to stabilize Zn anodes in aqueous electrolytes. However, there remain challenges involving the non-epitaxial electrodeposition of highly (002) textured Zn metal and the maintenance of (002) texture under deep cycling conditions. Herein, a novel organic imidazolium cations-assisted non-epitaxial electrodeposition strategy to texture electrodeposited Zn metals is developed. Taking the 1-butyl-3-methylimidazolium cation (Bmim+) as a paradigm additive, the as-prepared Zn film ((002)-Zn) manifests a compact structure and a highly (002) texture without containing (100) signal. Mechanistic studies reveal that Bmim+ featuring oriented adsorption on the Zn-(002) plane can reduce the growth rate of (002) plane to render the final exposure of (002) texture, and homogenize Zn nucleation and suppress H2 evolution to enable the compact electrodeposition. In addition, the formulated Bmim+-containing ZnSO4 electrolyte effectively sustains the (002) texture even under deep cycling conditions. Consequently, the combination of (002) texture and Bmim+-containing electrolyte endows the (002)-Zn electrode with superior cycling stability over 350h under 20 mAh cm-2 with 72.6% depth-of-discharge, and assures the stable operation of full Zn batteries with both coin-type and pouch-type configurations, significantly outperforming the (002)-Zn and commercial Zn-based batteries in Bmim+-free electrolytes.

Adaptive infrared radiation modulator using reversible metal electrodeposition with silicon carbide-based fabry-perot cavity

Conventional materials that statically modulate radiation in the infrared (IR) region of the electromagnetic spectrum underpin the performance of many entrenched technologies. The development of their adaptive variants, whereby the IR radiation properties dynamically change as a response to external stimuli, has emerged as an important unfulfilled scientific challenge. Here, by combining the silicon carbide (SiC)-based Fabry-Perot (FP) cavity effect with the traditional reversible metal electrodeposition device (RMED), where the FP cavity is used as a color filter to emit a particular wavelength and the RMED is used to reversibly modulate IR radiation, we develop an adaptive IR radiation modulator with large and uniform IR emissivity tunability (Δε ≥ 0.579) in the 3–14 µm region. A specific structural color which is a function of the SiC thickness can be simultaneously displayed when the modulator is in the low-emissivity mode. By varying the SiC thickness from 100 to 180 nm, a full gamut of colors spanning the entire visible spectrum can be achieved. Additionally, the modulator can exhibit fantastic patterns consisting of different structural colors with simple designs achieved. We believe that our findings may open opportunities for camouflage in multispectral detection and many technologies related to IR radiation management.

Recent Developments of Next-generation Smart Window using Metal Electrodeposition

Due to the energy and environmental crisis, indoor energy efficiency is of great importance. One of the solutions to cope with the problem is adopting a device with energy-saving functionality. From that perspective, smart window technology has received the foremost attention as of great potential, because it could modulate the solar energy stream such as light and heat. In addition to that, smart windows could offer visual aesthetic operation to our daily lives. Despite many technical attempts, no technology has been commercialized abruptly due to the restrictions or disadvantages. One of the rising options is a smart window based on reversible metal electrodeposition, as metal electrodeposits possess high contrast with color neutrality, and high coloration efficiency for privacy state. Since 2017, reversible metal electrodeposition-based smart window technology has been emerging, and advancing in terms of cycling, bistability, and color uniformity. This review aims to summarize the current technological trends and directions for the development of reversible metal electrodeposition-based smart window technologies.

Role of ionic liquids in the electrodeposition of metals

Green chemistry techniques have gained significant importance in advancing chemical engineering and processes in the modern era, contributing to the implementation of sustainable development strategies. Ionic liquids (ILs) at room temperature have emerged as versatile solvents in catalysis, separation science, and electrochemistry. Conventional synthesis of ILs typically involves a two-step process using refluxing solvents, which is time-consuming and requires large amounts of organic solvents. This study investigates the synthesis of alkylmethylimidazolium salts by the co-heating of haloalkanes and 1-methylimidazole, highlighting the role of ILs in green chemistry, particularly in the electrodeposition of metals. The objective of this research is to explore the impact of ILs on the electrodeposition process, aiming to develop environmentally friendly and efficient metal deposition methods. The methodology involves the preparation of ILs through a facile and sustainable approach, followed by the characterization of their physicochemical properties. The ILs are then utilized as electrolytes for metal electrodeposition, and the resulting metal films are analyzed for their morphology, structure, and properties. The findings of this study demonstrate the significant influence of ILs on metal electrodeposition. The ILs exhibit excellent solvation properties, facilitating the reduction and deposition of metals with improved control over morphology and structure. Additionally, the ILs offer the advantage of reduced environmental impact compared to traditional organic solvents. The main innovation lies in the application of ILs as green solvents in metal electrodeposition, contributing to the development of sustainable and efficient processes in the field of green chemistry.

Phase Engineering and Dispersion Stabilization of Cobalt toward Enhanced Hydrogen Evolution.

Phase engineering is promising to increase the intrinsic activity of the catalyst toward hydrogen evolution reaction (HER). However, the polymorphism interface is unstable due to the presence of metastable phases. Herein, phase engineering and dispersion stabilization are applied simultaneously to boost the HER activity of cobalt without sacrificing the stability. A fast and facile approach (plasma cathodic electro deposition) is developed to prepare cobalt film with a hetero-phase structure. The polymorphs of cobalt are realized through reduced stacking fault energy due to the doping of Mo, and the high temperature treatment resulted from the plasma discharge. Meanwhile, homogeneously dispersed oxide/carbide nanoparticles are produced from the reaction of plasma-induced oxygen/carbon atoms with electro-deposited metal. The existence of rich polymorphism interface and oxide/carbide help to facilitate H2 production by the tuning of electronic structure and the increase of active sites. Furthermore, oxide/carbide dispersoid effectively prevents the phase transition through a pinning effect on the grain boundary. As-prepared Co-hybrid/CoO_MoC exhibits both high HER activity and robust stability (44mV at 10mA cm-2, Tafel slope of 53.2mV dec-1, no degradation after 100 h test). The work reported here provides an alternate approach to the design of advanced HER catalysts for real application.