Facile Electrodeposition Research Articles

Boosting alkaline water splitting efficiency: NiOOH–MnOOH heterojunctions via in situ anodic oxidation

The facile electrodeposition and in situ anodic oxidation methods yield NiOOH–MnOOH heterojunctions on nickel foam, which exhibit exceptional electrocatalytic performance in alkaline media.

High-efficiency electrodeposition of magnesium alloy-based anodes for ultra-stable rechargeable magnesium-ion batteries.

Rechargeable magnesium batteries (RMBs) have attracted much attention because of their high theoretical volumetric capacity and high safety. However, the uneven deposition behavior, harmful corrosion reaction and poor stability of magnesium metal anodes have hindered the practical application of RMBs. Herein, we propose a facile alloy electrodeposition method to construct an artificial layer on an Mg anode. Experimental results show that the polarization of the symmetric magnesium alloy-based (Mg-Sn@Mg and Mg-Bi@Mg) cells is significantly reduced (∼0.05 V) at a current density of 0.1 mA cm-2. The symmetric cells using the prepared Mg alloy anodes exhibited lower voltage hysteresis and ultra-stable cycling performance at a higher density of 1.0 mA cm-2 over 700 h. The in situ optical microscopy study clearly demonstrated that the Mg dendrite formation was successfully retarded by the designed Mg-Sn and Mg-Bi alloy artificial protective layer on Mg anodes. The superiority of Mg-Sn@Mg and Mg-Bi@Mg was further confirmed in full cells using Mo6S8 as the cathode. Compared with the Mo6S8//Mg full cell, the Mo6S8//Mg-Sn@Mg and Mo6S8//Mg-Bi@Mg full cells maintained an ultra-stable electrochemical performance even after 5000 cycles. This proof-of-concept provides a novel scope for the artificial coating layers on Mg anodes prepared by alloy electrodeposition and can be extended to other alloy anodes (i.e. Mg-Cu@Mg and so on). This work provides an avenue for the design of practical and high-performance RMBs and beyond.

Supercapacitive properties of carbazole-containing cobalt(II) phthalocyanines/reduced graphene oxide composites.

This study aims to compare the effect of substituents (position and number) and reduced graphene oxide on the supercapacitive properties of cobalt(II) phthalocyanines. For this purpose, three new tetra- and octa-substituted cobalt(II) phthalocyanines bearing 9H-carbazol-2-yloxy groups on peripheral or non-peripheral positions (1-3) were synthesized. The characterization of the resultant cobalt(II) phthalocyanines was carried out by applying several spectroscopic approaches. The newly synthesized macromolecules were used for the functionalization of reduced graphene oxide (rGO). The obtained nanocomposites (rGO-(1-3)) were utilized for the modification of Ni foam (NiF) electrodes through a facile one-step electrodeposition strategy performed for electrochemical supercapacitor applications. Simultaneous polymerization of the cobalt phthalocyanines and electrochemically reduction of graphene oxide led to the formation of a fabricating layer on the surface of the NiF electrode. The resulting electropolymerized films were characterized by Raman, Fourier-transform infrared (FT-IR), and Field emission scanning electron microscope (FESEM) spectroscopic techniques as well as electrochemical methods. The prepared electrodes possessed superior electrochemical activities owing to the synergistic effect of the cobalt(II) phthalocyanines and rGO. All the modified electrodes displayed high supercapacitaive properties and the highest activity was obtained for the NiF/rGO2-1 electrode. The NiF/rGO2-1 electrode exhibited higher specific capacitance (655.2 F g-1 at 0.5 A g-1) than NiF/1 (338.0 F g-1). Additionally, a specific capacitance of 85.2% was obtained for NiF/rGO2-1 electrode after 3000 charge-discharge cycles. As a result, all the prepared metallophthalocyanines-reduced graphene oxide can be considered alternative agents to develop high performance-next-generation energy storage devices.

An artificial aluminum-tin alloy layer on aluminum metal anodes for ultra-stable rechargeable aluminum-ion batteries.

Rechargeable aluminum ion batteries (RAIBs) exhibit great potential for next-generation energy storage systems owing to the abundant resources, high theoretical volumetric capacity and light weight of the Al metal anode. However, the development of RAIBs based on Al metal anodes faces challenges such as dendrite formation, self-corrosion, and volume expansion at the anode/electrolyte interface, which needs the rational design of an aluminum anode for high-performance RAIBs. This work proposes a novel and low-cost strategy by utilizing an alloy electrodeposition method in a low-temperature molten salt system to fabricate an aluminum-tin (AlSn) alloy coating layer on copper foil as the anode for RAIBs, which successfully addresses the issues of dendrite formation and corrosion at the anode/electrolyte interface. The artificial AlSn alloy layer could enhance the active sites for metal Al homogeneous deposition and effectively retard the dendrite formation, which was verified by an in situ optical microscopy study. The symmetric AlSn@Cu cell demonstrates a low average overpotential of ∼38 mV at a current density of 0.5 mA cm-2 and a long-term lifespan of over 1100 h. Moreover, the AlSn@Cu//Mo6S8 full cells deliver a high capacity of 114.9 mA h g-1 at a current density of 100 mA g-1 and maintain ultra-stable cycling stability even over 1400 cycles with a ∼100% coulombic efficiency (CE) during the long-term charge/discharge processes. This facile alloy electrodeposition approach for designing high-performance Al-based anodes provides insights into the understanding of artificial interface chemistry on Al-based anodes and potentially accelerates the design of high-performance RAIBs.

Crystalline/amorphous nickel sulfide interface for high current density in alkaline HER: surface and volume confinement matters!

In this work, we demonstrate an interface on porous nickel foam (NN) between crystalline nickel sulfide and amorphous nickel sulfide (NNS/NNSx) adapting simple hydrothermal and facile electrodeposition processes, respectively. The developed electrocatalyst required a low overpotential of 15 mV to deliver a current density of 10 mA cm-2 and the interface intrinsically activates the electrocatalyst with an onset overpotential comparable to that of Pt in an alkaline hydrogen evolution reaction.

Selective electrooxidation of 5-hydroxymethylfurfural at low working potentials promoted by 3D hierarchical Cu(OH)2@Ni3Co1-layered double hydroxide architecture with oxygen vacancies.

Selective electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is of great significance in the manufacture of fine chemicals, liquid fuels, pharmaceuticals, plastics, etc., but still suffers from the high potential input, resulting in high electricity consumption. Developing active, low-cost and stable electrocatalysts is crucial for this electrochemical reaction at low working potentials. Herein, a three-dimensional (3D) hierarchical Cu(OH)2@Ni3Co1-layered double hydroxide architecture with abundant oxygen vacancies (Vo) was synthesized by facile electrodeposition of Ni3Co1-LDH nanosheets on copper foam (CF) supported-Cu(OH)2 nanorods (CF/Cu(OH)2@Ni3Co1-LDH) for the selective electrooxidation of HMF to FDCA. The 3D hierarchical architecture of the Cu(OH)2 nanorod core loaded with Ni3Co1-LDH nanosheet shell facilitates the rapid transfer of charges and exposes more active sites. The synergistic effect of the core-shell nanoarray structure, atomic level dispersion of Ni and Co on LDH laminates, and rich Vo gives 98.12% conversion of HMF, 98.64% yield and 91.71% selectivity for FDCA at a low working potential of 1.0 V vs. RHE. In addition, CF/Cu(OH)2@Ni3Co1-LDH exhibits superior stability by maintaining 93.26% conversion of HMF, 93.65% yield and 91.57% selectivity of FDCA after eight successive cycles, showing the immense potential of utilizing electrochemical conversion for biomass.

Biocompatible Co-P Metallic Glasses with Superior Degradation Tolerance in Physiological Environments.

Metallic glasses represent a class of metallic alloys with a fully amorphous structure and attractive properties, making them promising in bioimplant applications. Here, the degradation tolerance of biocompatible cobalt-phosphorus (Co-P) metallic glasses was studied in a simulated physiological environment. The metallic glasses were synthesized in the form of coatings through a facile electrodeposition approach. This method utilizes their outstanding surface characteristics and bypasses the size limitations usually associated with their bulk counterparts. The Co-P alloys showed exceptional tribological response with ∼14% lower coefficient of friction and 2 orders of magnitude lesser wear rate compared to SS316 stainless steel. In addition, the Co-P alloys showed a 3 times higher hardness and 4 times higher hardness/modulus ratio compared to SS316, indicating better elastic recovery under dynamic shear stresses that are common in load-bearing bioimplants. The Co-P metallic glasses exhibited excellent hemocompatibility and cytocompatibility in terms of lower platelet adhesion, spreading, and aggregation, a hemolysis ratio lower than 1%, and enhanced surface wettability, suggesting a superlative performance in bioimplant applications.

A rapid one-step electrodeposition method for fabrication of the superhydrophobic nickel/cobalt alloy surfaces with excellent robustness and durability features

The artificial superhydrophobic surfaces were successfully assembled on various substrates by adjusting surface roughness and reducing surface energy. In this work, a series of superhydrophobic Ni/Co alloy (SNCA) surfaces with hierarchical micro/nano rough structures were prepared on brass substrates by a facile one-step electrodeposition method. Based on these surfaces, the influences of manufacturing parameters and their structure on the wettability of SNCA were well discussed. The results confirmed that SNCAt under the synergy of multi-optimal parameters (m, i, t) displays a more ordered cone-flower structure, showing excellent superhydrophobicity (WCA = 167.9°, WSA = 3.2°), and the massive pollutants spread on its surface can be easily taken away by the rolling water droplets within 40 s. It is reassuring to know that SNCAt surface still retains good superhydrophobicity after undergoing blade scraping, tape stripping, sandpaper cyclic wear, heat treatment and chemical corrosion, which shows long-term durability. The corrosion protection capability of the as-fabricated SNCA was also evaluated by electrochemical corrosion techniques. The results show that SNCA has outstanding corrosion inhibition performance in simulated seawater solution, and especially the protection efficiency of SNCAt can reach above 98 %. In conclusion, the existence of superhydrophobic surface can be regarded as a barrier, and the perfect interface of gas-liquid can effectively inhibit the permeation of corrosive ions. Therefore, the superhydrophobic surface with robustness and durability will be a promising alternative technique for corrosion protection.

Breaking Free - Unlocking the Potential of Dynamic Hydrogen Bubble Templating Materials

In recent years, porous electrodes for electrochemical conversion devices, such as low-temperature fuel cells or water electrolyzers, have been engineered to address issues related to mass transport to and within the catalyst. For example, the addition of a layer with reduced pore size facing the catalyst layer (i.e., microporous layer) results in an increased performance[1–3]. Furthermore, chemical[4], as well as mechanical[5,6]. methods of creating dedicated liquid and gas pathways in the porous electrodes, have been investigated with promising results, highlighting the need for further optimization of state-of-the-art materials with regards to multi-phase transport. The range of possible modifications is intrinsically limited by the microstructure of the material they are applied to and add cost and complexity to the already costly electrode production procedure, motivating the development of novel materials which contain these desired features, offer a large morphological design space, and are cost competitive.To tackle these stringent targets, we investigate the dynamic hydrogen bubble templating (DHBT) method to generate hierarchical structures containing both a pore size gradient as well as dedicated water and gas pathways in the form of bimodal pore size distributions. It leverages simultaneous deposition of a metal and gas evolution on the same surface to form complex structures from solution using electricity. It results in a hierarchical structure of primary pores (~5-40 µm) separated by porous walls containing secondary pores (10-1000 nm) . This type of material has been used successfully to improve boiling heat transfer[7], another process limited by the counterflow of liquid and gas. They have also been investigated as high surface area material for microbial anodes[8] and have been postulated to be appealing in other electrochemical devices such as batteries or fuel cells[9]. A significant hurdle to unlock the full potential of DHBT foams is the attachment of the foam to the solid electrode surface it is generated on. The presence of the electrode blocks the transport of media in the through-plane direction of the foam and thereby prevents its use in many electrochemical applications. Due to its fragile nature, separation of the foam from this surface easily damages the structure, which is why previous research was done exclusively in the presence of the electrode. Overcoming this limitation would enable new applications for DHBT foams and has the potential to address a wide range of problems in electrochemical systems related to porous media.In this talk, I will discuss our work towards creating free-standing, hierarchically structured metal electrodes through DHBT and the developments needed to adapt this material for the use in electrochemical systems. Owing to its well-studied synthetic parameters and facile electrodeposition, we chose copper foams to advance DHBT materials in terms of characterization and mechanical properties. As a key step of the synthesis route, we realized a method to manufacture free-standing sheets from this material from copper metal while preserving its delicate microstructure. This was supported by an optimization of synthesis parameters to improve and ensure adequate mechanical stability of the freestanding foams after isolation. This development enables the application of a wide range of characterization methods such as XTM, BET, SEM and interferometry and I will discuss how the synthesis parameters link to the resulting material microstructure. Building on this initial success, current work focuses on the transferring this knowledge to the synthesis of foams made from other metals which are more relevant to electrochemical applications such as nickel for the use in alkaline electrolyzers and paves the way to develop DHBT material into the next generation transport layer for electrochemical systems.

(Invited) Research Progress of Electrocatalyst and MEA of PEM Fuel Cell and Water Electrolyser

The successful commercialization of PEM fuel cell and water electrolyser is determined by the performance, durability, and cost of electrocatalyst and MEA. Compared with conventional electrodes, nanoarray electrodes feature enhanced mass transport thanks to continuous proton and electron transport channels. Herein, a series of nanoarray electrodes were developed directly as the electrodes for PEM fuel cells and water electrolysers. A catalyst layer based on porous Pt−Ni nanobelt arrays were prepared by the magnetron sputtering of Pt and Ni on a sacrificed template, followed by acid etching. The porous Pt−Ni nanobelt arrays-based catalyst layer exhibited superior fuel cell performance in H2/air conditions and RH 40%. The performance of the MEA with porous Pt−Ni nanobelt arrays reached 366.6 and 597.6 mW cm−2 with Pt loadings of 36.5 μg cm−2/36.5 μg cm−2 and 108.9 μg cm−2/108.9 μg cm−2 at the cathode/anode, respectively. Besides, a WO3 nanoarray electrode with a heterogeneous IrRu coating was prepared via a facile electrodeposition approach. The obtained IrRu@WO3 electrode exhibits a competitive overpotential of 245 mV at 10 mA cm−2. A single cell enables a current density of 4.5 A cm−2 at 2.13 V with the Ir loading of 115 mg cm−2. The nanoarray structure remains unchanged in a single-cell during a 500-h stability test. In sum, these work highlights a new approach to enhance the performance and durability for PEM fuel cells and water electrolysers.

Unveiling the morphological influence of nitrogen-doped carbonized wood anchored 3D transition metal oxide microarchitectures on catalytic activity: A trifunctional electrocatalyst for sensing and energy conversion

The rational construction and advancement of binder-free, self-standing, and cost-effective electrodes endowed with highly active trifunctional electrocatalysts represent a pivotal nexus between the research domains of energy and healthcare applications. However, the lack of proficient non-precious-metal trifunctional electrocatalysts bridging the aforementioned research domains remains a pinnacle barrier. Herein, we proposed distinct fabrication protocols to construct morphologically diverse three-dimensional (3D) CuO microarchitectures directly docked over the naturally inherited carbon channels of nitrogen-doped carbonized wood (NCW) (CuO@NCW) obtained by the carbonization of waste wood monoliths and explored the efficacy of different catalytic designs towards the trifunctional performances on non-enzymatic glucose sensing and glucose oxidation-assisted water splitting. Among the diverse binder-free engineered electrodes, CuO@NCW obtained via the facile electrodeposition (E) route (dubbed as CuO-E@NCW) demonstrated proficient electrocatalytic trifunctionality benefitting from the allied merits of the robustly anchored 3D porous dendritic architectures equipped with ample porosity and momentous interconnectivity. The as-fabricated CuO-E@NCW electrode as a glucose sensor displays two broad linear ranges between 0.01 and 0.5 mM and 0.5–4.0 mM with corresponding elevated sensitivities of 24.6 and 7.2 mA mM−1 cm−2, with a lower limit of detection of 0.0013 mM (S/N = 3). Besides, this best-performing electrode delivers a high current density of 50 mA cm−2 with a low cell voltage of 1.39 V in the glucose electrolysis system, which is 170 mV lower compared with stereotypical alkaline water splitting.

A Grafted Hybrid Nanosheet Array Architecture Enables Efficient Bifunctional Oxygen Catalytic Electrodes for Rechargeable Lithium−Oxygen Batteries

AbstractTo fully manifest the high energy densities of lithium−oxygen (Li−O2) batteries, bifunctional catalytic cathodes that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are mandatorily required. However, catalysts with intrinsic bifunctional catalytic activities are limited in practice. In addition, the practical utilization rate of oxygen catalytic cathodes is usually lower due to the deposition of insoluble discharge product Li2O2. To address these issues, this work proposes a grafted hybrid nanosheet array architecture to enable efficient bifunctional oxygen catalytic cathodes for Li−O2 batteries. As a demonstration, Co3O4 nanosheet arrays (MnO2−Co3O4@CC) grafted with MnO2 nanosheets are prepared on carbon cloth by facile electrodeposition followed by calcination in air. The mutually perpendicular Co3O4 and MnO2 nanosheets in the grafted architecture enable both the ORR catalytically active site of MnO2 and the OER catalytically active site of Co3O4 easily accessible during repeated cycling. Thus, the synergistic bifunctional catalysis of hybrid MnO2−Co3O4@CC is effectively realized to deliver a high specific capacity of 8115 mA h g−1 and a low overall overpotential of 0.64 V. This work provides a universal and effective approach for fabricating various efficient catalytic electrodes via the facile integration of different nanomaterials on nanoarray architectures.

Electrodeposited polyaniline based carbon nanotubes fiber as efficient counter electrode in wire-shaped dye sensitized solar cells

Electrodeposited polyaniline over the carbon nanotubes fiber (CNTF) has been investigated as potential candidate to substitutes the Pt based auxiliary electrodes in unidimensional fibrous solar cells. CNTF, with excellent electrical and mechanical properties, modified with conducting polymer (polyaniline) via facile electrodeposition process which employed as cathodic materials showed efficient electrochemical reduction of triiodide ions in the fiber shaped dye-sensitized solar cells. Scanning electron microscopic analysis showed the efficacious integration of conducting polymer over the CNTF surface. The admirable electrocatalytic behavior of the fabricated electrode has investigated by electrochemical impedance spectroscopy and cyclic voltammetry. Current density and voltage (J–V) curves are used to quantify the photovoltaic performance of devices with different counter electrodes with fixed photoanode. With lower peak to peak separation, improved current density and better fill factor, exhibited the superior efficiency of modified electrode (PANI@CNTF). As compared to pristine fiber, polyaniline modification showed the outstanding performance with improved photovoltaics and electrochemical parameters measured by the J–V and CV curves, respectively.

Highly Efficient Cobalt Sulfide Heterostructures Fabricated on Nickel Foam Electrodes for Oxygen Evolution Reaction in Alkaline Water Electrolysis Cells

Non-noble metal electrocatalysts for the oxygen evolution reaction (OER) have recently gained particular attention. In the present work, a facile one-step electrodeposition method is applied in situ to synthesize cobalt sulfide nanostructures on nickel foam (NF) electrodes. For the first time, a systematic study is carried out on the impact of the Co/S molar ratio on the structural, morphological, and electrochemical characteristics of Ni-based OER electrodes by employing Co(NO3)2·6 H2O and CH4N2S as Co and S precursors, respectively. The optimum performance was obtained for an equimolar Co:S ratio (1:1), whereas sulfur-rich or Co-rich electrodes resulted in an inferior behavior. In particular, the CoxSy@NF electrode with Co/S (1:1) exhibited the lowest overpotential value at 10 mA cm−2 (0.28 V) and a Tafel slope of 95 mV dec−1, offering, in addition, a high double-layer capacitance (CDL) of 10.7 mF cm−2. Electrochemical impedance spectroscopy (EIS) measurements confirmed the crucial effect of the Co/S ratio on the charge-transfer reaction rate, which is maximized for a Co:S molar ratio of 1:1. Moreover, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) were conducted to gain insights into the impact of the Co/S ratio on the structural and morphological characteristics of the electrodes. Notably, the CoxSy@NF electrocatalyst with an equimolar Co:S ratio presented a 3D flower-like nanosheet morphology, offering an increased electrochemically active surface area (ESCA) and improved OER kinetics.

One-step electrodeposition of NiS heterostructures on nickel foam electrodes for hydrogen evolution reaction: on the impact of thiourea content

Herein, we report on the one-step growth of nickel sulfide (NiS) heterostructures on nickel foam (NF) substrate via a facile electrodeposition method, employing Ni(NO3)2.6H2O and CH4N2S as Ni and S precursors, respectively. For the first time, a systematic study was carried out on the impact of the Ni/S molar ratio on the electrochemical performance of as-prepared electrodes for water splitting. The optimum performance was obtained for a Ni:S ratio equal to 2:1, whereas lower or higher ratios resulted in much inferior performance. The NiS@NF electrode with a Ni:S ratio of 2:1 exhibited the lowest overpotentials |η10| = 136 mV, |η100| = 209 mV, extremely low Tafel slope (60 mV dec-1), and very high double layer capacitance value (2.78 mF cm-2). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and X-ray photoelectron spectroscopy (XPS) revealed the formation of coral-like nanoarchitecture, resulting in enhanced HER activity.

MoO3/BiVO4 heterojunction modified with cobalt-manganese layered double hydroxide cocatalyst for photoelectrochemical water oxidation

To improve the charge recombination and poor oxygen evolution reaction (OER) kinetics of BiVO4, in this paper, a high-performance CoMn-LDH/MoO3/BiVO4 photoanode was synthesized by a simple electrodeposition and calcination method. CoMn-LDH/MoO3/BiVO4 shows a photocurrent density of 3.78 mA cm−2 at 1.23 V vs. RHE, which is 3.78 times higher than that of pure BiVO4 with negative shift onset potentials of 330 mV. The maximum applied bias photon-to-current efficiency (ABPE) and incident photon-to-current conversion efficiency (IPCE) are 1.24 % and 55.5 %, respectively, which are 13.8 and 12.5 times higher than those of pure BiVO4. In-depth studies demonstrate that the MoO3/BiVO4 heterojunction can better drive the transfer of photogenerated carriers and suppress bulk charge recombination, CoMn-LDH improves the OER kinetics and broadens the absorption of visible light, their synergistic effect significantly enhances charge separation and light harvesting of BiVO4. This work provides a facile electrodeposition method to fabricate highly efficient photoanodes for solar-driven water splitting.

BiOI/AgI/Ag plasmonic heterostructure for efficient photoelectrochemical water splitting

BiOI-based photocathode has attracted much attention for photoelectrochemical (PEC) water splitting application. Here, we have designed a BiOI/AgI/Ag plasmonic heterostructure through a facile electrodeposition combined with ion-exchange and illumination approach. The work function difference between BiOI and AgI brings favorable interfacial band bending, and the Ag nanoparticle exhibits localized surface plasmonic effect to boost the carrier transfer. Thus, the BiOI/AgI/Ag photocathode achieves superior current density of −1.02 mA cm−2 at 0 V vs. RHE for 200 min, which is 50 times than that of pristine BiOI. These results pave a way for promising PEC water splitting using BiOI-based heterostructure photocathodes.

A facile and efficient method for preparing La-doped Co3O4 by electrodeposition as an efficient air cathode in rechargeable zinc-air batteries: Role of oxygen vacancies

A rechargeable zinc-air battery (ZAB) is a promising candidate for simple and low-cost energy storage systems. However, preparing the air cathode material using a binder-free method and a bifunctional catalyst is still the major challenge in the field. Herein, we demonstrate the effect of different La contents doped into the Co3O4 spinel structure in the presence of oxygen vacancies prepared by a facile and efficient electrodeposition technique on the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ZAB performance. Incorporating the La dopant into the Co3O4 improves the OER and ORR performances and thus enhances the specific capacity and energy density of ZAB. The optimal La-doping amount in the CoLa-1 catalyst demonstrates high feasibility for practical application with a capacity of 780 ± 24 mAh/g and an energy density of 901 ± 39 mW g−1, significantly outperforming the pristine Co3O4. The stability and cycling tests reveal good durability performance after 300 cycles and 100 h of testing without degradation, which is much more stable than the benchmark Pt/C + RuO2 electrode. The performance enhancement is attributed to the synergetic effect of high active surface area, low charge transfer resistance, and optimal oxygen vacancies. A kinetic micromechanism is proposed to illustrate the importance of the oxygen vacancy amount in trapping oxygen gas and maximizing the number of ORR and OER reactions.

Bifunctional CuO@CoV layered double hydroxide (LDH) core–shell heterostructure for electrochemical energy storage and electrocatalysis

The state-of-the-art designing and development of materials is an inevitable prior step for an effective solution regarding energy resources. In the context of supercapacitors (SCs) and electrocatalysis, it remains a challenge to fabricate electrode materials with high specific capacitance, high conductivity and lower overpotential. Here, a core–shell structure is prepared via a facile two-step electrodeposition method using CuO core and electrodeposited binary CoV LDH as the shell and used as a SC electrode and an electrocatalyst. For comparison, the CuO and Cu@CoV LDH electrodes are also prepared using a similar method. The CuO@CoV LDH core–shell electrode exhibits an areal capacitance of 206 mF cm−2 accompanied by an excellent stability of 88 % over 5000 cycles at a current density of 10 mA cm−2. This areal capacitance is far better than that obtained for CuO (49 mF cm−2) and Cu@CoV LDH (58 mF cm−2) electrodes. The symmetric device is fabricated using core–shell heterostructure demonstrating an energy density of 62.8 mWh cm−2 and power density of 985 mW cm−2. Moreover, the CuO@CoV LDH core–shell structure demonstrates an excellent oxygen evolution reaction (OER) catalytic activity with an overpotential of 329 mV and a Tafel slope of 65 mV dec-1. This study opens a new route for the fabrication of CuO@CoV LDH core–shell structure via facile electrodeposition method for the electrochemical energy storage and catalytic activity.

Porous Ni–Fe–Cr electrocatalyst for the oxygen and hydrogen evolution reaction via facile one-step electrodeposition

A high-performance bifunctional Ni–Fe–Cr electrocatalyst with a coral reef-like porous structure was fabricated by facile one-step electrodeposition at a high cathodic current density of 8 A/cm2 for 30 min in an optimal electrodeposition bath containing 80 g/L CrCl3 and 1 M NH4Cl. The highly porous Ni–Fe–Cr electrocatalyst exhibits extremely low overpotential of 234 mV for oxygen evolution reaction (OER) and 13 mVRHE for hydrogen evolution reaction (HER) in 1 M KOH at a current density of 10 mA/cm2, respectively. The excellent performance of the Ni–Fe–Cr electrocatalyst can be attributed to the modulation of the electronic structure due to the incorporation of Cr enhanced performance capabilities of the porous Ni–Fe–Cr originate from the increased electrochemical active surface area (ECSA), which is 22 times larger than that of thin Ni–Fe–Cr. Moreover, the catalyst exhibits high stability towards the OER and HER in an alkaline solution for 36 h. This work offers a facile synthesis method by which to create a highly porous Ni–Fe–Cr electrocatalyst by electrodeposition and a strategy for increasing the catalytic activity by controlling the pore size.