Nanosheet Arrays Research Articles

Study on microwave absorption performance of nickel cobalt bimetallic nanosheet arrays @ hydrophilic carbon cloth composite with core-sheath structure

Magnetic metal/carbon matrix composites have gained significant attention as vital microwave absorption materials (MAMs) in recent years, owing to their multifarious microwave loss mechanisms, adjustable chemical composition, and microstructure. In this study, we describe the successful synthesis of nickel-cobalt bimetallic nanosheet arrays @ hydrophilic carbon cloth (NiCo-BNSAs @ HCC) composites with a distinctive core-sheath structure, low density, and high toughness using a solvothermal method followed by a high-temperature pyrolysis process. Despite their low density and high toughness, these composites exhibit outstanding MA properties at low matching thicknesses. Among them, S2 exhibited the minimum reflection loss (RLmin) of −75.4 dB at 1.35 mm, with its optimal effective absorption bandwidth (EAB, RL＜−10 dB) extending to 3.6 GHz at 1.10 mm. Our analysis indicates that the incorporation of NiCo-BNSAs nanosheets not only enhances the multiple scattering of EM waves but also improves interfacial polarization loss and dipole polarization loss. This study provides valuable insights into the rational construction of high-performance magnetic metal/ carbon matrix MAMs with a core-sheath structure.

Defect engineering associated with cationic vacancies for promoting electrocatalytic water splitting in iron-doped Ni2P nanosheet arrays

Transition metal phosphides are highly efficient catalysts that do not rely on noble metals, which have shown great potential in replacing noble metal catalysts and contributing to the advancement of the electrocatalytic hydrogen production industry. To further enhance the catalytic performance of transition metal phosphides, researchers have discovered that cationic vacancy defects can be utilized to regulate their electronic structure, thereby improving their catalytic properties. In this research, we present the successful synthesis of a bifunctional Ni2P electrocatalyst (VFe-Ni2P) with cationic vacancy defects through electrodeposition and acid etching techniques. The introduction of cationic vacancies after acid etching is confirmed by electron paramagnetic resonance (EPR) spectroscopy. The VFe-Ni2P electrocatalyst demonstrates excellent catalytic performance in alkaline environments, achieving a current density of 10 mA∙cm−2 at an overpotential of 52 mV for the hydrogen evolution reaction (HER), and the same current density with an overpotential of 154 mV for the oxygen evolution reaction (OER). Additionally, the VFe-Ni2P/NF electrode exhibits remarkable stability over 1000 cyclic voltammetric cycles for both HER and OER. This study presents a novel approach for the synthesis and performance control of highly-efficient transition metal phosphide electrocatalysts, which holds significant importance in the development and design of new energy materials.

Self-supported iridium integrated leaf-shaped Fe3O4 columnar arrays toward highly efficient oxygen evolution at industrial-grade current density

The sluggish kinetics for oxygen evolution reaction (OER) significantly impede the practical applications of electrocatalytic water splitting technology for renewable energy source. The facile design of self-supporting electrocatalysts with high activity and stability for OER catalysis at industrial-grade current density is of paramount significance to mitigate the above bottlenecks. We report herein the construction of iron foam (IF) self-supported Ir-magnetite (Ir-Fe3O4/IF-T-x) electrode via galvanic replacement between IrCl62− ions and Fe2+ in Fe3O4 nanosheet arrays, which is simply synthesized by annealing IF in air and subsequent thermal treatment in reducing atmosphere. Such pre-treatment enables the growth of leaf-like Fe3O4 nanosheet arrays with rich Fe2+ species and oxygen defects, which facilitate the depositing of Ir on the surface of nanosheet arrays and thereby promote the electrochemical OER performance in basic electrolyte. Impressively, the optimized Ir-Fe3O4/IF-400-2 delivers the highest electrocatalytic activity with a low overpotential of 316 mV to obtain industrial-grade current density of 500 mA cm−2 for alkaline OER. Meanwhile, the catalyst still shows good long-term stability after 36 h V-t test at 100 mA cm−2. This study offers a simple and efficient pathway to prepare self-supporting electrode for alkaline OER at industrial-grade current density.

Wire-type flexible micro-supercapacitor based on MOF-assisted sulfide nano-arrays on dendritic CuCoP and V2O5-polypyrrole/nanocellulose hydrogel

Wire/fiber-type micro-supercapacitors (micro-SCs) have great potentials in next-generation wearable and portable energy supply devices, due to their low weight, high flexibility, small size and excellent reliability. Herein, we designed 2D-3D S-doped CoZnNi-OH/CuCoP positive microelectrode with hierarchical structure on 1D metal fiber substrate for high-capacitance fibrous micro-SCs. Such unique architecture, which 2D S-doped CoZnNi-OH nanosheet arrays vertically aligned on 1D Cu wire garnished with 3D dendritic CuCoP through CoZn-MOF template, exposed ample electroactive sites, created robust electrical and mechanical joint between nanostructured material and metal fiber, and promote the transport/diffusion rate of ions. The achieved 2D-3D S-doped CoZnNi-OH/CuCoP/CW microelectrode exhibited the areal/volumetric/length capacitances of 2.9 F cm−2, 290.07 F cm−3, and 348 mF cm−1 at 4 mA cm−2, respectively, which is 18 times of the sulfide directly co-electrodeposited on 3D CuCoP foam without MOF template. Besides, negative microelectrode was prepared through electrochemical deposition of V2O5-PPy on 1D carbon fiber substrate decorated with rGO-nanocellulose (NC) hydrogel. The electrical double layer capacitance behavior combined with pseudocapacitive properties enhances charge storage performance of fibrous microelectrode in terms of specific capacitance, cycle stability and rate capability. The fabricated solid-state 2D-3D S-doped CoZnNi-OH/CuCoP/CW//V2O5-PPy/rGO-NC/CF micro-SC presents high areal energy density of 127.62 µWh cm−2 at a power density of 1.83 mW cm−2 and durability (93.7 % retention after 5000 cycles) with excellent mechanical flexibility. Giving the versatility of 1D carbon/metal fiber substrates, template-assisted 3D architecture, MOF-derived sulfide nanoarrays, and NC chemical reactivity, the proposed strategy can be used for construction of other next-generation miniaturized portable electronics.

High-mass-loading cobalt iron phosphide@nickel vanadium layered double hydroxide heterogeneous nanosheet arrays for hybrid supercapacitors

Designing multidimensional heterostructures on flexible substrates is an efficient approach to resolve the low energy density of supercapacitors. Herein, a three-dimensional (3D) porous cobalt iron phosphide (CoFeP)@nickel vanadium-layered double hydroxide (NiV-LDH) heterostructure has been prepared anchored on carbon cloth (CC) substrate. In this nanoarchitecture, NiV-LDH nanosheets are densely wrapped on the surface of CoFeP nanosheets, which forms a hierarchically porous framework with an enlarged surface area and accessible pore channels. Benefiting from the strong interaction and synergistic effect between CoFeP and NiV-LDH, the well-defined heterostructure can realize simultaneously rich redox active sites, rapid reaction dynamics, and good structural stability. Thus, the binder-free CoFeP@NiV-LDH electrode with a high mass loading of 6.47 mg cm−2 displays a significantly increased specific capacity of 903.1C g−1 (2.35C cm−2) at 1 A g−1 and enhanced rate capability when compared to pristine CoFeP and NiV-LDH. Additionally, the assembled hybrid supercapacitor (HSC) yields an energy density of 77.9 Wh kg−1/0.98 Wh cm−2 and excellent long-term stability. This research proposes a rational route for designing heterogeneous micro-/nanoarchitectures with commercial-level mass loading for the practical application of high-energy-density supercapacitors.

Flexible monolithic Pt/CuO-Fe2O3/TiO2 catalysts integrated on Ti mesh for efficient NO removal via CO-SCR reaction

This study reports on the development of highly-efficient Pt/CuO-Fe2O3/TiO2 monolithic catalysts for the low-temperature conversion of NO to N2 via CO-SCR. In this case, ultrathin TiO2 nanosheet arrays are designed to in situ grow on flexible Ti mesh to provide more spaces/areas for the loading of highly-dispersed Fe2O3 and CuO active components. Furthermore, Pt nanoparticles with an average size of 1.30 nm are effectively decorated on the surface of CuO-Fe2O3/TiO2. The H2-TPR and NO-TPD results demonstrate that the excellent synergistic effect between TiO2, CuO, Fe2O3 and trace amounts of Pt is conducive to enhance the adsorption of NO and finally promote the CO-SCR. The obtained Pt/CuO-Fe2O3/TiO2 catalysts exhibit excellent CO-SCR performance with 100 % NO conversion, and 100 % N2 selectivity at 250 °C, showing great potential of de-NOx application by using toxic CO as reductant in industry.

Constructing defect-rich S-doped NiMoO4/Ni3S2 2D/2D heterostructures as highly efficient and stable bifunctional electrocatalysts for overall water splitting

The development of economical, efficient, and durable bifunctional catalyst for overall water splitting is an attractive and challenging task. Herein, a novel defect-rich 2D/2D heterostructure is constructed by vertically growing S-doped NiMoO4 (NiMoO4-S) nanosheets on nickel sulfide (Ni3S2) nanosheet arrays supported on nickel foam (NF) using a two-step hydrothermal method. Benefiting from the hierarchical sheet-on-sheet heterogeneous nanostructure and abundant oxygen vacancies for more active sites, efficient electronic/mass transfer, and fast gas release, the synthesized NiMoO4-S/Ni3S2/NF electrode exhibits excellent electrocatalytic performance for HER (η10 mA cm−2 = 107 mV) and OER (η50 mA cm−2 = 285 mV). The alkaline water electrolyzer with NiMoO4-S/Ni3S2/NF as the positive and negative electrodes can provide a current density of 10 mA cm−2 with the potential of 1.52 V, which is below that of the commercial Pt||RuO2/NF system or many other reported systems. More importantly, the alkaline water electrolyzer offers a current density of 100 mA cm−2 at 1.85 V with outstanding durability of over 50 h. This research points to a promising route in designing transition metal-based bifunctional electrocatalysts for large-scale energy conversion applications.

Nanosheets array-induced nanofluidic channels toward efficient primary batteries-coordinated textiles

Flexible hygroelectric generators (HEGs) that derive affordable and sustainable electricity power from omnipresent moisture are promising candidates for smart textile electronics. However, the desired compatibility of high output current and continuous operating voltage is still challenging for wearable HEGs to meet the ever-increasing nanotechnological requirements. Herein, we rationally design and finely synthesize conductive carbonized silk fabrics with in situ growth of SnO/SnO2 nanosheet arrays, which are successfully employed to fabricate high-efficiency wearable HEGs with a maximal power density of 26.66 μW·cm−2 by sandwiching with MXene/cotton fabrics and Al electrodes. Impressively, the vertically interlaced SnO/SnO2 nanosheet arrays supply abundant nanofluidic channels for rapid water diffusive flow with a high flow potential. Combined with the excellent moisture absorption and retention of MXene/cotton textiles, these prepared HEGs process sustained voltage and current outputs of 0.932 V and 0.434 mA over 20,000 s. These flexible HEGs are capable of application in self-powered sensors and micro power supplies, delivering a fresh strategy for the rational design of high-performance and sustainable textile-based electronics.

Study on growth behavior and properties of LDH nanosheet arrays enhanced Ni-based coatings on Mg-Li alloy

For the application of lightweight alloys, the corrosion and wear problems of magnesium-lithium (Mg-Li) alloys have always been important problems that cannot be ignored. The coupling protection of multiple technologies has gradually become a new trend. In this study, layered double hydroxides (LDH) nanosheet arrays were in-situ grown on Ni-P coating by the electroless plating technology combined with hydrothermal synthesis technology. The optimum deposition conditions (temperature-time-pH) were selected by orthogonal test. The surface morphology, structure, corrosion resistance and wear resistance of LDH/Ni composite coatings under different conditions were systematically studied by SEM, XRD, FT-IR, DSC, electrochemical and tribological tests. The growth mechanism of LDH suitable for Ni-P coating surface was proposed by analyzing the growth process of LDH nanosheet arrays. The results showed that the condition of 125 °C-12 h-13 was conducive to the growth of LDH nanosheet arrays. Compared with the Ni-P coating and the composite coating under other conditions, the LDH125°C-12h-13/Ni composite coating has the lowest self-etching current density (7.50 × 10−7 A·cm−2) and the average friction coefficient (0.35). The defect sealing effect and Cl− barrier property of LDH effectively improved the corrosion resistance of the coating. The frictional properties were improved by lubrication and heat absorption properties of LDH. In addition, it was found that the growth of LDH on the Ni-P coating surface followed the mechanism of “deposition nucleation-diffusion growth”.

Enhanced Metal-Support Interactions Boost the Electrocatalytic Water Splitting of Supported Ruthenium Nanoparticles on a Ni3N/NiO Heterojunction at Industrial CurrentDensity.

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure-induced-strategy to optimize the metal-support interaction (MSI) and the EWS activity of Ru-Ni3N/NiO. Density function theory (DFT) calculations firstly predicted that the Ni3N/NiO-heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru-Ni3N/NiO, compared to Ru-Ni3N and Ru-NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof-of-concept, the Ru-Ni3N/NiO catalyst with 2D Ni3N/NiO-heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which owns an excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm-2, respectively. Furthermore, the Ru-Ni3N/NiO-based EWS device can realize an industrial current density (1000 mA cm-2) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm-2) in alkaline pure water.

Synthesis of Quaternary (Ni, Co, Cu)Se2 Nanosheet Arrays on Carbon Cloth for Non-Enzymatic Glucose Determination

Unlike transition metal oxides and sulfides, transition metal-based selenides display higher electrical conductivity, more electroactive unsaturated edge sites, and better chemical stability, which have found extensive usage in electrocatalysis. In this work, simple hydrothermal and solvothermal procedures were employed to synthesize quaternary (Ni, Co, Cu)Se2 nanosheet arrays on carbon cloth (CC) to measure glucose. The conductivity of the material can be effectively elevated by adding Se element to form selenides, and the synergistic effect between the three selenides can improve the electrocatalytic performance. Consequently, in the ranges of 0.01–600 μM and 600–9000 μM, respectively, the current response of the synthesized material to glucose concentration exhibited linear relationships. The sensor demonstrated excellent sensitivity and a low detection limit of 5.82 nM. Furthermore, the practical applicability of the constructed biosensor was proved by using it to quantify the amount of glucose in human serum.

Enhanced Metal‐Support Interactions Boost the Electrocatalytic Water Splitting of Supported Ruthenium Nanoparticles on a Ni3N/NiO Heterojunction at Industrial Current Density

AbstractDeveloping highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure‐induced‐strategy to optimize the metal‐support interaction (MSI) and the EWS activity of Ru‐Ni3N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni3N/NiO‐heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru‐Ni3N/NiO compared to Ru‐Ni3N and Ru‐NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof‐of‐concept, the Ru‐Ni3N/NiO catalyst with a 2D Ni3N/NiO‐heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm−2, respectively. Furthermore, the Ru‐Ni3N/NiO‐based EWS device can realize an industrial current density (1000 mA cm−2) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm−2) in alkaline pure water.

In situ construction of S-doped NiFe-layered double hydroxide nanoarrays on porous reduced graphene oxide as efficient oxygen evolution electrocatalysts for electrolytic cells

The application of NiFe-layered double hydroxide (NiFe-LDH) as electrocatalysts for oxygen evolution reaction (OER) is seriously limited owing to low conductivity, insufficient active sites and self-aggregation. The construction of anion-doped NiFe-LDH nanoarray structures with ideal electrochemical activity is an effective strategy. Herein, we report a facile solvothermal approach for the synthesis of S-doped NiFe-LDH nanosheets loaded in situ on porous reduced graphene oxide (rGO) to form a composite with nanosheet array structure (S-NiFe-LDH/rGO) for OER. The S-NiFe-LDH/rGO nanosheet array ensures a large specific surface area, abundant accessible active sites and high stability. The moderate S doping in NiFe-LDH can tune the local electronic structures of Ni and Fe to optimize the binding of metal sites with reaction intermediates, thus enhancing the OER activity. The S-NiFe-LDH/rGO electrocatalyst shows the small OER overpotential of 264 mV at 10 mA cm−2 and the low Tafel slope of 55 mV dec−1. Moreover, S-NiFe-LDH/rGO displays good durability and structural stability due to the strong anchoring effect. The assembled two-electrode S-NiFe-LDH/rGO||Pt electrolytic cell exhibits a low cell voltage of 1.53 V at 10 mA cm−2, which is superior to the RuO2||Pt benchmark cell (1.60 V), indicating the practical feasibility for water electrolysis. This design strategy provides a promising insight into the fabrication of advanced OER non-noble metal electrocatalysts.

ZIF in situ transformation hollow porous self-supporting CoZn-LDH@CuO electrode for electrochemical sensing of glucose and H2O2

A 3D hollow CoZn-LDH@CuO nanosheet array was prepared in situ by using CoZn-ZIF skeleton grown on Cu(OH)2 nanorods with copper foam as precursor. The catalyst materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray photoelectron spectroscopy (XPS). The synergistic effect between the three metals and the hollow layered nanosheet array structure make the catalyst have larger specific surface area and more exposed active sites, which can effectively improve the electron transfer rate. Using CoZn-LDH@CuO NSA/CF as the working electrode, glucose and H2O2 can be detected with sensitivity of 11,200 (μA mM−1 cm−2) and 4585 (μA mM−1 cm), respectively. The linear ranges were 2 μM − 3 mM and 0.8 μM − 3.5 mM and the detection limits is 0.17 μM (S/N = 3). The sensor had excellent stability, selectivity, fast response time (≤3 s), and the recoveries in the actual sample detection is 99.6 %-103.1 %. This strategy provides a new idea for the design and preparation of catalytic electrodes in the field of electrochemical sensing.

Selenate promoted stability improvement of nickel selenide nanosheet array with an amorphous NiOOH layer for seawater oxidation

Seawater electrolysis offers significant potential for green hydrogen production, the presence of harmful chlorine species, nevertheless, can cause severe anode corrosion. Here, we present our recent finding that selenate anions adsorbed nickel selenide nanosheet array with an amorphous NiOOH layer on Ni foam (NiSe2@NiOOH/NF) serves as a high-efficiency and durable electrocatalyst for oxygen evolution reaction (OER) in alkaline seawater. It requires an overpotential of 460 mV to obtain 500 mA cm−2. Impressively, it shows at least 100 h of electrolysis tolerance at 500 mA cm−2. Insights from electrochemical in situ Raman spectroscopy and chlorine extraction tests unveil that selenite undergoes oxidation to selenate during the OER test, effectively suppressing hypochlorite generation.

Self-Supporting Superaerophobic Electrode with Ni–Mo Anchoring on Cu Nanosheet Arrays Derived from Copper Foam for Hydrogen Evolution

Self-Supporting Superaerophobic Electrode with Ni–Mo Anchoring on Cu Nanosheet Arrays Derived from Copper Foam for Hydrogen Evolution

Modulating surface electron density of hydrophilic/high-conductive MXene/Ni(OH)2/NF heterostructures for efficient asymmetric supercapacitors

To address the growing demand for efficient and stable energy storage in the context of green energy, in this study, an acid etching method was employed to in-situ grow Ni(OH)2 nanosheet arrays on a nickel foam (NF) substrate. Subsequently, negatively charged Ti3C2Tx MXene nanosheets were electrophoretically deposited onto the Ni(OH)2/NF surface to result in a MXene/Ni(OH)2/NF composite electrode material. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed the homogeneous dispersion distribution of nanosheets on the material surface. The composite material exhibited high electrical conductivity and good hydrophilicity by rapid water infiltration within 150 ms. Furthermore, the Motte-Schottky effect establishes a distinctive pathway for electron transfer, which leads to the creation of electron vacancies or ‘holes’ on the MXene surface. This phenomenon significantly boosts MXene's electrochemical activity and enhances its affinity for OH− ions in the electrolyte, which consequently improves the performance of electrochemical capacitors.Electrochemical tests verified that the prepared MXene/Ni(OH)2/NF electrode displayed an areal specific capacitance of 0.223 mAh cm−2 at a current density of 1 mA cm−2. The electrode displayed excellent rate performance with a capacity retention rate of 71 % when the current density was increased by five times. In addition, the assembled asymmetric capacitor with MXene/Ni(OH)2/NF electrode demonstrated an excellent cycling stability with only a 16.38 % capacity loss after 5000 cycles. It also exhibited the remarkable specific capacitance and long-term stability by achieving a high energy density of 43.68 Wh kg−1 and a power density of 424.96 W kg−1. These results highlight the electrode's exceptional performance in terms of energy storage and power delivery.

Construction of Binder-Free, Self-Supported, Hetero-Core-Shell Honeycomb Structured CuCo2 O4 @Ni0.5 Co0.5 (OH)2 with Abundant Mesopores and High Conductivity for High-Performance Energy Storage.

Clever and rational design of structural hierarchy, along with precise component adjustment, holds profound significance for the construction of high-performance supercapacitor electrode materials. In this study, a binder-free self-supported CCO@N0.5 C0.5 OH/NF cathode material is constructed with hierarchical hetero-core-shell honeycomb nanostructure by first growing CuCo2 O4 (CCO) nanopin arrays uniformly on highly conductive nickel foam (NF) substrate, and then anchoring Ni0.5 Co0.5 (OH)2 (N0.5 C0.5 OH) bimetallic hydroxide nanosheet arrays on the CCO nanopin arrays by adjusting the molar ratio of Ni(OH)2 and Co(OH)2 . The constructed CCO@N0.5 C0.5 OH/NF electrode material showcases a wealth of multivalent metal ions and mesopores, along with good electrical conductivity, excellent electrochemical reaction rates, and robust long-term performance (capacitance retention rate of 87.2%). The CCO@N0.5 C0.5 OH/NF electrode, benefiting from the hierarchical structure of the material and the exceptional synergy between multiple components, demonstrates an excellent specific capacitance (2553.6 F g-1 at 1 A g-1 ). Furthermore, the assembled asymmetric CCO@N0.5 C0.5 OH/NF//AC/NF supercapacitor demonstrates a high energy density (70.1Wh kg-1 at 850W kg-1 ), and maintains robust capacitance cycling stability performance (83.7%) after undergoing 10000 successive charges and discharges. It is noteworthy that the assembled supercapacitor exhibits an operating voltage (1.7V) that is well above the theoretical value (1.5V).

Co-doped NiFe-LDH nanosheets arrays supported on nickel foam as an efficient oxygen evolution electrocatalysis

In the field of water electrolysis for hydrogen production, NiFe-layered double hydroxides (NiFe-LDH) is currently one of the most excellent oxygen evolution electrocatalyst. However, its application in this field is limited due to its low durability, low conductivity and few active sites. In this work, we present a Co-introduced fine-modulated NiFe-LDH performance strategy to construct Co-doped NiFe-LDH nanosheets arrays supported on nickel foam (Co-NiFe-LDH/NF). The optimized Co-NiFe-LDH/NF showed ultralow overpotentials at 211, 237, 261 and 281 mV at 50, 100, 200 and 300 mA cm−2 current densities, separately, with an extremely low Tafel slope (40 mV dec−1). The Co-NiFe-LDH/NF was highly stable during the constant current test, and the potential increased by only 10 and 13 mV after 100 h stability test at 200 and 300 mA cm−2. Notably, it also works stably at the 500 and 1000 mA cm−2 very high current densities, representing high potential of commercial application. The theoretical calculation showed that: (1) Introducing Co into NiFe-LDH can reduce the energy barrier of OH* conversion to O* and increase the activity of OER; (2) Considering the formation energy, Co is more likely to replace Fe site in NiFe-LDH than Ni site; (3) The energy barrier, differential charge and partial density of states analysis show that the best OER performance is obtained when the Fe-to-Co ratio of 2:1, and the theoretical calculation is consistent with the experimental verification. This work provides a simple and effective method for the design and construction of doping elements into NiFe-LDH electrocatalysts for efficient water oxidation, and promoted NiFe-LDH material application in commercial alkaline water electrolysis cell.

Understanding the Plasmonic Effect of Enhanced Photodegradation with Au Nanoparticle Decorated ZnO Nanosheet Arrays under Visible Light Irradiation.

Plasmonic-enhanced photocatalysis using visible light is considered a promising strategy for pollution photodegradation. However, there is still a lack of comprehensive and quantitative understanding of the underlying mechanisms and interactions involved. In this study, we employed a two-step process to fabricate arrays of ZnO nanosheets decorated with Au nanoparticles (Au-ZnO NS). Various characterization techniques were used to examine the morphological, structural, and chemical properties of the fabricated Au-ZnO NS array. Furthermore, we systematically investigated the photocatalytic degradation of methyl orange under visible light irradiation using Au-ZnO NS arrays prepared with varying numbers of photochemical reduction cycles. The results indicated that as the number of photochemical reduction cycles increased, the photodegradation efficiency initially increased but subsequently decreased. Under visible light irradiation, the Au-ZnO NS array obtained via four cycles of photochemical reduction exhibits the highest photocatalytic degradation rate of methyl orange 0.00926 min-1, which is six times higher than that of the ZnO NS array. To gain a better understanding of the plasmonic effect on photodegradation performance, we utilized electromagnetic simulations to quantitatively investigate the enhancement of electric fields in the Au-ZnO NS array. The simulations clearly presented the nonlinear dependencies of electric field intensity on the distribution of Au nanoparticles and the wavelength of radiation light, leading to a nonlinear enhancement of hot electron injection and eventual plasmonic photodegradation. The simulated model, corresponding to four cycles of photochemical reduction, exhibits the highest electric field intensity at 550 nm, which can be attributed to its strong plasmonic effect. This work provides mechanistic insights into plasmonic photocatalysts for utilizing visible light and represents a promising strategy for the rational design of high-performance visible light photocatalysts.