Hydrothermal Electrodeposition Research Articles

(Digital Presentation) Hydrothermal Electrodeposition of Molybdenum Sulfide Toward Electrochemical CO2 Reduction Catalysts

The search and development of efficient carbon dioxide (CO2) reduction reaction electrocatalysts is a hot topic in this era of global warming. Among material candidates for sustainable and cost−effective applications, metal sulfides have attracted attention as promising nature-inspired materials due to multiple adsorption sites which are enhanced by the covalent character of sulfur.Molybdenum sulfides (MoS2) is one of the trandition metal dichalcogenides (TMDs) and possesses three kinds of struture; namely, metastable octahedral structure with high electronic conductivity (1T), stable triangular prism structure with low electronic conductivity (2H) and insulating rhombohedral structure (3R). Among them, 1T phase has been widely applied as catalysts for various reactions such as electrochemical nitrogen reduction reaction and electro/photochemical hydrogen evolution reaction. Since the structure of MoS2 largely affect its catalytic and other material property, synthetic process to control their bulk and even local structure should be explored to expand their availability as functional materials. Especially, our previous work (J. Phys. Chem.C, 126, 2772, 2022) demonstrated that metal-sufur bonding length is one of the key parameter to control carbon monoxide production selectivity from electrochemical CO2 reduction.Here in this work, hydrothermal electrodeposition was applied to MoS2 synthesis to control their local structure. Recently, our group developed hydrothermal electrochemical flow reactor which enables the electrochemistry under hydrothermal condition with separate control of temperature and pressure. Using this reactor, hydrothermal electrodeposition of manganese oxides (MnO2) was conducted and samples exhibited higher electrochemical oxygen evolution activity than ones prepared with conventional methods. Also, the characterization results of electrodeposited MnO2 under hydrothermal condition showed the possiblity that morphology and lattice spacing can be controled by changing deposition temperature and pressure, respectively. Thus, we predicted our hydrothermal electrodeposition technique is useful to control the local structure of materials.The hydrothermal electrodeposition of MoS2 were conducted under various temperature and pressure conditions and those samples were characterized with X-ray diffraction (XRD). Also, the effect of the deposition temperature and pressure on sample local structure was examined with Pair Disribution Function analysis of XRD and Extended X-ray Absorption Fine Structure analysis using synchrotron radiation. The electrochemical CO2 reduction experiments using hydrothermally depositted MoS2 samples revealed that the product selectivity for CO2 reduction was changed with deposition pressure. Thus, we confirmed that our hydrothermal electrochemical deposition can be applicable to the synthesis of metal sulfide-based CO2 reduction electrocatalysts, whose local structures are tuned.

Enhanced performance of hybrid supercapacitors by the synergistic effect of Co(OH)2 nanosheets and NiMn layered hydroxides

A self-supporting composite electrode material with a unique three-dimensional structure was synthesized by in-situ growth of nanoscale NiMnLDH-Co(OH)2 on a nickel foam substrate via hydrothermal electrodeposition. The 3D layer of NiMnLDH-Co(OH)2 provided abundant reactive sites for electrochemical reactions, ensuring a solid and conductive skeleton for charge transfer and resulting in significant enhancement of electrochemical performance. The composite material showed a strong synergistic effect between the small nano-sheet Co(OH)2 and NiMnLDH, which promoted reaction kinetics, while the nickel foam substrate acted as a structural conductivity agent, stabilizer, and good conductive medium. The composite electrode showed impressive electrochemical performance, achieving a specific capacitance of 1870F g−1 at 1 A g−1 and retaining 87% capacitance after 3000 charge–discharge cycles, even at a high current density of 10 A g−1. Moreover, the resulting NiMnLDH-Co(OH)2//AC asymmetric supercapacitor (ASC) demonstrated remarkable specific energy of 58.2 Wh kg−1 at a specific power of 1200 W kg−1, along with outstanding cycle stability (89% capacitance retention after 5000 cycles at 10 A g−1). More importantly, DFT calculations reveal that NiMnLDH-Co(OH)2 facilitates charge transfer, accelerating surface redox reactions and increasing specific capacitance. This study presents a promising approach towards designing and developing advanced electrode materials for high-performance supercapacitors.

Microwave hydrothermal electrodeposition of nickel carbonate hydroxide/cobalt hydroxide film on nickel foam for cement-based structural supercapacitors

Electroactive electrode materials for cement-based structural supercapacitors suffer from poor interface contacts with ceramic electrolytes and current collectors due to their poor adhesive to the current collectors and severe reactions during cement hydration process, leading to their inferior capacitive performance relative to conventional supercapacitors. Herein, microwave hydrothermal electrodeposition was developed to deposit a robust composite film of Ni2(CO3) (OH)2/Co(OH)2 as an electroactive electrode material onto nickel foam. Effects of Ni/Co molar ratio of 0.5, 1, 1.5, and 2 on the microstructure and electrochemical properties of the film electrode were investigated in detail. Subsequently, the film electrode with the optimal electrochemical performance was compared with that by hydrothermal deposition with no microwave involvement. The results showed all the resultant films by microwave hydrothermal electrodeposition showed a crooked sheet morphology with a polycrystalline structure containing lots of dislocations. Among them, the film of a Ni/Co molar ratio of 1 presented the optimal capacitive performance (a specific capacity of 632.8 (1.88) C/g(F/cm2) at 1 (2.97) A/g (mA/cm2), a superlong cycling life of 30,000 cycles at 10 A/g with a capacity retention of 80.4%) and demonstrated better electrochemical and adhesive properties than that prepared by hydrothermal electrodeposition with no microwave involvement. Finally, this optimal film electrode was employed as the cathode, active carbon as the anode and polyacrylic acid (PAA)-KOH-aluminate cement as the structural electrolyte, an hybrid structural supercapacitor device was assembled, and exhibited a compressive strength of as high as 37.2 MPa and a ionic conductivity of 8.2 mS/cm, and deliver excellent electrochemical performance (specific capacitance of 415.31 mF/cm2 at 0.5 mA/cm2, and 80.1% capacitance retention of after 8000 cycles at 1 mA/cm2), which is the best capacitive performance among the reported cement-based structural supercapacitors in the form of civil engineering. Our experimental results reveal that microwave hydrothermal electrodeposition could be utilized to fabricate high-performance electrode materials on nickel foam for structural supercapacitors.

Rational Assembly of the NiMoP/NiCoZn Heterostructure Electrocatalyst for the Hydrogen Evolution Reaction at High Current Densities

Developing a cost-effective hydrogen (H2) evolution electrocatalyst can effectively solve the problem of environmental pollution caused by excessive fossil fuel use. Herein, we report an innovative synthetic strategy, involving hydrothermal electrodeposition of a NiCoZn film on commercial carbon fiber paper (CFP) and in situ cyclic voltammetric electrodeposition of NiMoP to prepare a heterostructure electrocatalyst (NiMoP/NiCoZn/CFP) with synergistic electrocatalytic activity toward the hydrogen evolution reaction (HER). To deliver high current densities of 500 and 1000 mA cm–2, the NiMoP/NiCoZn/CFP electrode only required overpotentials of 230 and 268 mV, respectively, which were considerably superior to those of Pt–C/CFP (457 and 592 mV, respectively). Moreover, this electrode exhibited excellent ultrastability (40 h at 500 mA cm–2 or 80 h at 1 A cm–2). The superior electrocatalytic HER activity is attributed to (1) cooperative electronic interactions between NiMoP and NiCoZn in the heterointerface and (2) the complete wettability, which is advantageous for gas formation and desorption and considerably reduces bubble adhesion and reaction resistance. This work provides a rational electrodeposition strategy for constructing heterointerface electrocatalysts for H2 production at high current densities.

Hydrangea-like nanosheets of Co(OH)2@NiFe-LDH/NF as an efficient electrocatalyst for the oxygen evolution reaction

Synthesis of a novel polymetallic hydroxide composite using a rapid hydrothermal–electrodeposition method for efficient oxygen evolution reaction.

Rapid, one-step fabrication of MoS2 electrocatalysts by hydrothermal electrodeposition

MoS2 structures with large surface areas and edges for use as electrocatalysts in the hydrogen evolution reaction (HER) are typically synthesized via solvothermal and hydrothermal methods. However, to utilize the fabricated particles as electrodes, they should be applied on substrates in the form of inks; this requires additional processing. Furthermore, if the electrode has a three-dimensional structure with more than two sides, applying the ink to the entire surface is difficult. Therefore, there is a requirement for a thin-film deposition process based on a fast reaction that does not require toxic substances and can be used for one-pot electrode fabrication. In this study, we present a rapid, one-step hydrothermal electrodeposition technique for the formation of MoS2 thin films on glassy carbon substrates. The MoS2 electrocatalysts fabricated using this method have surfaces that are rich in metallic phases, and they exhibit good activity as hydrogen evolution catalysts. This hydrothermal electrodeposition technique is expected to be broadly applicable to various electrodes and other technologies.

One-step preparation of cobalt nickel oxide hydroxide@cobalt sulfide heterostructure film on Ni foam through hydrothermal electrodeposition for supercapacitors

Development of technologies or strategies to achieve efficient and low-cost electrode materials for high-performance supercapacitors is highly desirable in the field of renewable energy. In this study, a novel route for preparation of a two-phase film of 4Ni(OH)2·NiOOH@Co9S8 on Ni foam was developed through chemical bath followed by hydrothermal electrodeposition, which was carried out by a one-step process in an autoclave. This strategy first grew nano-sheets of 4Ni(OH)2·NiOOH phase crystals (NiCo-OH) on Ni foam in the stage of elevating temperature, and then start to deposit Co9S8 phase species (CoS) onto the surface of NiC-oOH through hydrothermal electrodeposition during heat preservation, forming a cheek to cheek heterostructure. The resultant composite film as an electrode material for supercapacitors could deliver specific capacities of 1083.6 (2.709), 856.8 (2.142), 624.6 (1.562), 502.2 (1.256), 419.4 (1.049) and 279.2 (0.698) C·g−1 (C·cm−2) at 5, 10, 20, 30, 40 and 50 mA·cm−2, and long lifespan (no decay after 12,000 cycles), which is far higher than the single NiCo-OH film. The excellent capacitive performance is ascribed to the synergistic effect of NiCo-OH and CoS which could provide fast ion and electron conductions, respectively. When the NiCo-OH/CoS composite was utilized as the positive electrode material and active carbon as the negative material, an asymmetric supercapacitor device (ASC) was assembled and could achieve high specific capacitance (1.52 F·cm−2 at 5 mA·cm−2), good rate capability (a capacitance retention of 59% with an 10-fold increase in the discharge current density), high energy density (8.2 Wh·kg−1 (15.1 mWh·cm−3) at 542.8 W·kg−1 (111.1 mW·cm−3)), high power density (5440.2 W·kg−1 (1111.1 mW·cm−3) at 39.8 Wh·kg−1 (8.1 mWh·cm−3)) and excellent cycling stability (a capacitance retention of 85.5% after 12,000 cycles). The results prove that this novel strategy exhibits a promising prospect of direct fabrication of a heterostructure electrode with advantageous features, like convenience and time/cost saving, for high-performance supercapacitors.

(Invited) Electrodeposition of Manganese Oxides Utilizing Hydrothermal Electrochemical Technique

Hydrothermal electrochemistry can conduct electrochemical experiments under high temperature and pressure conditions and is one of the useful methods to fabricate size-controllable and highly crystalline materials. Although this technique has been applied to electrodeposition of metal oxides like BaTiO3 (Yoshimura et al., Jpn. J. Appl. Phys., 28, L2007, 1989), precise control and examination of electrochemical process was hard to be achieved in previous reactors because they adopted two-electrode systems. Moreover, reaction pressure was determined by temperature, so it is difficult to discuss their specific contribution to the electrochemical process.Recently, we have developed hydrothermal electrochemical reactor in which three-electrode system was adopted in order to control and monitor the electrochemical process precisely. This system also achieves independent control of temperature and pressure so that we can discuss their contributions to the final products. Here in this work, we attempted to fabricate Manganese oxide thin film with electrodeposition technique under different temperature and pressure, and examined their electrochemical water oxidation activity. Manganese oxides are prepared in industry with electrodeposition technique, so they are good candidates as model compounds to examine the property of our home-made hydrothermal electrochemical reactor.MnO2 was deposited on Ti substrate with galvanostatic condition of 10 mA /cm2 for 20 min utilizing 0.5 M MnSO4 / 0.2 M H2SO4 aqueous solution as a precursor. Based on XRD analysis, all deposited samples were ε-MnO2. When we increase deposition temperature, XRD peaks got sharpen, indicating the crystallinity increased. SEM observation clarified their morphological difference. Namely, MnO2 deposited at 160℃ possessed needle-like structure, while spherical structure was observed for sample deposited at 100℃. To examine the effect of pressure on deposition products, we conducted electrodeposition under different pressure from 0.1 to 4 MPa while maintaining temperature at 100℃. As a result, XRD peaks were slightly shifted depending on pressure. This means lattice constant is controllable by regulating deposition pressure.Their electrochemical water oxidation activity also demonstrated the advantage of hydrothermal electrodeposition compared with conventional technique. After annealing at 200℃, 160℃-electrodeposited sample exhibited superior activity to 100℃-deposited sample. Although the elucidation of the reason for higher catalytic activity is future work, those results indicate our hydrothermal electrochemical technique is widely applicable to material synthesis such as metal oxides, metal sulfides, and so on. Figure 1

Self-Supportive Mesoporous Ni/Co/Fe Phosphosulfide Nanorods Derived from Novel Hydrothermal Electrodeposition as a Highly Efficient Electrocatalyst for Overall Water Splitting.

Low cost and highly efficient bifuctional catalysts for overall water electrolysis have drawn considerable interests over the past several decades. Here, rationally synthesized mesoporous nanorods of nickel-cobalt-iron-sulfur-phosphorus composites are tightly self-supported on Ni foam as a high-performance, low cost, and stable bifunctional electrocatalyst for water electrolysis. The targeted designing and rational fabrication give rise to the nanorod-like morphology with large surface area and excellent conductivity. The NiCoFe-PS nanorod/NF can reach 10 mA cm-2 at a small overpotential of 195 mV with a Tafel slope of 40.3 mV dec-1 for the oxygen evolution reaction and 97.8 mV with 51.8 mV dec-1 for the hydrogen evolution reaction. Thus, this bifunctional catalyst shows low potentials of 1.52 and 1.76 V at 10 and 50 mA cm-2 toward overall water splitting with excellent stability for over 200 h, which are superior to most non-noble metal-based bifunctional electrocatalysts recently. This work provides a new strategy to fabricate multiple metal-P/S composites with the mesoporous nanorod-like structure as bifunctional catalysts for overall water splitting.

A simplified process for preparing adhesive hydroxyapatite coatings on carbon/carbon composites

A monetite (CaHPO4) coating prepared by hydrothermal electro-deposition technology (HET) owned a well adhesive strength on Carbon/Carbon (C/C) composites, showing a promising prospect in orthopedic and teeth implants. However, hydrophobic C/C surface had to be pre-treated by solutions containing oxidants, such as H2O2, (NH4)2S2O8, to form chemical bonding with the calcium phosphate coating before the deposition, which is a time-consuming and tedious procedure. To simplify the CaHPO4 preparation, H2O2 was directly added into an electrolyte for depositing a well-bonded CaHPO4 coating by HET, denoted as H-CaHPO4, on naked C/C composites. For comparison, another CaHPO4 coating was prepared on H2O2 pre-treated C/C by HET under the same conditions, designated by N-CaHPO4. Both the CaHPO4 coatings were converted to HA coatings via a post-hydrothermal treatment in an ammonia solution, correspondingly defined as H-HA and N-HA. Interestingly, scratch tests showed H-HA coating on C/C through the simplified HET method had a critical load of 29 N, nearly twice as high as N-HA coating. And H-HA coating on naked C/C showed a more compact microstructure and a lower Ca/P atomic ratio in comparison with N-HA coating on H2O2 pre-treated C/C. The reasons for the change in the microstructure and the improvement in the adhesion of the coatings on C/C were discussed. Besides, in-vitro SBF tests and cell experiments indicated that H-HA coating had a better bioactivity and cell biocompatibility than N-HA coating.

Hydrothermal electrodeposition incorporated with CVD-polymerisation to tune PPy@MnO2 interlinked core-shell nanowires on carbon fabric for flexible solid-state asymmetric supercapacitors

Herein, a hydrothermal electrodeposition method was developed to synthesize MnO2 interlinked nanowires on carbon fabric (CF). Facile chemical vapour deposition (CVD)-polymerization was subsequently employed to deposit polypyrrole (PPy) films on MnO2 nanowires to construct a hierarchical PPy@MnO2 structure on CF (PPy@MnO2@CF). This unique 1D structure is beneficial due to its high electrical conductivity, structure stabilization and fast electrochemical kinetics. The PPy@MnO2@CF showed a maximum areal capacitance of 1.24 F cm−2 at a current density of 1 mA cm−2. A flexible solid-state asymmetric supercapacitor (FSASC) was assembled using PPy@MnO2@CF and Fe2O3@CF as positive and negative electrodes, respectively. The FSASC delivered a maximal energy density of 1.93 mWh cm−3 at a power density of 9.8 mW cm−3 and a long term life with 92.6% of initial capacitance after 10,000 cycles. In addition, the device exhibited exceptional flexibility and excellent mechanical stability after a 200-bending-cycle test, suggesting that it is close to practical application in flexible electronics.

Novel hydrothermal electrodeposition to fabricate mesoporous film of Ni0.8Fe0.2 nanosheets for high performance oxygen evolution reaction

Here, we report a new synthetic strategy to fabricate mesoporous film of Ni0.8Fe0.2 nanosheets for high performance oxygen evolution reaction (OER). Mesoporous Ni0.8Fe0.2 film self-supported on stainless steel mesh (SLS) was prepared via a novel hydrothermal electrodeposition process. Hydrothermally driven electrodeposition method showed significant advantages toward OER: (1) high temperature makes H2 generated on the cathode to overflow faster. Both the gas generated on the cathode and hydrothermal condition impacted coating surface, hence, the film possessed more active sites to improve OER properties and (2) hydrothermal condition improved the crystallization of the coating leading to excellent electrode stability under OER test. The mesoporous Ni0.8Fe0.2 film exhibited an overpotential of 206 mV at 10 mA cm−2 (i.e., 1.436 V vs. RHE), a Tafel slope of 64 mV dec−1 and excellent stability after 2 × 105 s (more than 55 h) at 10 mA cm−2. The superior OER properties could be attributed to the film’s novel synthetic process, porous structure and high electrical conductivity. This work shows a new strategy to fabricate mesoporous alloy films as OER catalysts.

Cuprous oxide thin films grown by hydrothermal electrochemical deposition technique

Semiconducting cuprous oxide films were grown by a hydrothermal electro-deposition technique on metal (Cu) and glass (ITO) substrates between 60°C and 100°C. X-ray diffraction studies reveal the formation of cubic cuprous oxide films in different preferred orientations depending upon the deposition technique used. Film growth, uniformity, grain size, optical band gap and photoelectrochemical response were found to improve in the hydrothermal electrochemical deposition technique.

Effect of Cerium Doping on Morphology and Physical Properties of α-Fe2O3 Films Prepared by Hydrothermal Electrodeposition

In this study, electrochemical growth of Ce-doped α-Fe2O3 films is reported. Electrodeposition at 75°C and also a combined hydrothermal-electrochemical method to obtain hematite are presented. Both acidic and neutral plating solutions were used for the depositions. Ferric oxyhydroxide is produced by electrodeposition at 75°C and converted to hematite phase after annealing. Hydrothermal-electrodeposition at 130°C results in formation of hematite phase directly. The effect of temperature, deposition solution and cerium ion amount on the morphology and physical properties of hematite films are characterized.

Influence of ethanol on the HAp coatings prepared by hydrothermal electrodeposition on C/C composites

Hydroxyapatite (HAp) coatings were prepared on carbon/carbon (C/C) composites with a novel hydrothermal electrodeposition method. The as-prepared HAp coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, and scanning electron microscope (SEM) analyses. The influence of ethanol on the phases and microstructures of HAp coatings was investigated. Results show that the coatings’ crystallization shows little change with the increase in ethanol content up to 15%, but the density, homogeneousness, and adhesion with the substrate of HAp coatings obviously improved. The deposition mechanism of the HAp coating is also discussed. Thus, it is helpful to get dense and good-adhesion HAp coatings when ethanol is added into the solution during the hydrothermal electrodeposition process.

Preparation of Hydroxyapatite Coatings on Carbon/Carbon Composites by a Hydrothermal Electrodeposition Process

Hydroxyapatite (HAp) coatings were prepared by a hydrothermal electrodeposition method on Carbon/carbon (C/C) composites. The as-prepared HAp coatings were characterized by XRD and SEM analyses. The influence of hydrothermal temperature on the phase and surface microstructures of HAp coatings and the corresponding deposition kinetics were particularly investigated. Results show that with the increase of hydrothermal temperature, the crystallinity, density and homogenous of the prepared HAp coatings are improved. The deposition rate also increases with the increase of hydrothermal temperature. The deposition activation energy of HAp coatings by the hydrothermal electrodeposition process is calculated to be 25.89 kJ/mol.

Influence of deposition voltage on phases and microstructure of hydroxyapatite coatings prepared on C–C composites by hydrothermal electrodeposition

Hydroxyapatite (HAp) coatings were prepared on the surfaces of carbon–carbon (C–C) composites by a novel hydrothermal electrodeposition method. The as prepared HAp coatings were characterised by X-ray diffraction and scanning electron microscopy. The degree of crystallinity, density and homogeneity of the HAp coatings were found to increase with increasing deposition voltage. The deposition rate also increased with increasing deposition voltage.