Nanosheet Arrays Research Articles

Rh, Co, and N-doped titanium mesh-based carbon nanosheet arrays for enhanced nitrite reduction reaction and ammonia generation

The electrocatalytic transformation of nitrite pollutants into valuable ammonia is crucial for the nitrogen cycle. However, the complex multi-reaction process necessitates the development of highly efficient and selective electrocatalysts. This study focuses on the creation of Rh-doped Co@NC anchored on a titanium mesh as an electrocatalyst to enhance the electrocatalytic nitrite reduction reaction (eNO2RR) for NH3 synthesis. By doping a trace amount of Rh within zeolitic imidazolate framework-67 nanosheets and subsequently pyrolyzing the material, uniformly distributed Rh and Co nanoparticles are anchored onto N-functionalized porous carbon nanosheet arrays. Consequently, the three-dimensional electrode enhances mass and electron transfer while providing abundant surface-exposed active sites for NH3 generation through eNO2RR. The Rh0.6 wt%–Co@NC/TM electrocatalyst, with a minimal Rh loading of 0.6 wt%, exhibits the highest Faradaic efficiency of 98.8 ± 0.7 % at −0.3 V, along with an NH3 yield of 1777.1 ± 7.0 μmol h−1 cm−2 at −0.7 V. Additionally, the electrocatalyst demonstrates exceptional durability over 20 consecutive cycles and remarkable environmental adaptability. Extensive experimental studies reveal that the superior performance of Rh0.6 wt%–Co@NC/TM arises from the synergistic catalysis between Co and Rh, which enhances NO2– adsorption and the production of active hydrogen for eNO2RR to NH3 synthesis. This research highlights that Rh incorporation facilitates the kinetics of eNO2RR and offers valuable insights for the development of efficient electrocatalysts towards NH3 synthesis.

In situ fabrication of Cu2O array electrode for efficient detection of acetaminophen

In this paper, Cu(OH)2 nanosheet arrays were directly grown in an upright manner on the surface of copper foam (CF) through a simple solvent reaction, followed by the successful reduction of Cu(OH)2 into Cu2O using hydrazine hydrate vapor, resulting in a binder-free Cu2O@CF array electrode. The in situ growth technique guarantees robust bonding between Cu2O and the conductive substrate, thereby enhancing electron transfer among various electrode components. Additionally, the vertically aligned array structures facilitate rapid penetration and transfer of the analyte, while also allowing for thorough exposure of the electroactive surfaces to the electrolyte. When utilized as an adhesive-free biosensor, the obtained Cu2O@CF array electrode exhibited sensitive catalytic oxidation activity toward acetaminophen (AP), providing a wide linear range of 2–200 [Formula: see text]M and a low detection limit of 0.6 [Formula: see text]M for AP detection. Furthermore, the developed Cu2O@CF array electrode was successfully utilized to detect AP in medicine samples. With its simple fabrication method, broad linear range, low detection limit, and excellent stability, this electrode holds significant promise for the detection of AP in pharmaceuticals.

Modulating the synergy of Pt single atoms and quantum dots on NiFe LDH for efficient and robust hydrogen evolution

Hydrogen evolution reaction (HER) from water electrolysis is an ideal alternative solution to address the energy crisis and develop clean energy. However, the construction of an efficient electrocatalyst with multiple active sites that can ensure high metal utilization and promote reaction kinetics simultaneously still leaves a major challenge. Herein, we present a facile strategy to synthesize a HER catalyst comprising Pt single atoms (PtSA) anchored in Fe vacancies and Pt quantum dots (PtQD) on the surface of NiFe LDH. Benefitting from the hierarchical and ultrathin nanosheet arrays and strong electronic interaction between PtSA/PtQD and NiFe LDH matrix, the optimized sample (PtSA/QD-NiFeV9 LDH) exhibits outstanding HER performance in 1 M KOH with ultra-low overpotentials of 20 and 67 mV at 10 and 100 mA cm−2, respectively, outperforming the benchmark Pt/C electrocatalyst. In addition, the electrolyzer using PtSA/QD-NiFeV9 LDH as a cathode requires voltages of only 1.48 and 1.73 V to yield current densities of 10 and 1000 mA cm−2, respectively. The combination of in situ tests and density functional theory (DFT) calculations reveal that the synergy of PtSA and PtQD can optimize the kinetics of water dissociation and hydrogen desorption, thus the Volmer-Tafel pathway prevailing the HER process. This work provides a promising surface engineering strategy to develop catalysts for efficient and robust hydrogen evolution.

Mesh-supported V2O5-WO3/TiO2 nanosheet array catalysts for efficient removal of NOx

Mesh-supported V2O5-WO3/TiO2 nanosheet array catalysts for efficient removal of NOx

Crystalline-to-Amorphous Transformation and Charge Redistribution Induced by Anion–Cation Double Substitution on 3D Ni(OH)2 Ultrathin Nanosheet Arrays Enable Urea-Assisted Energy-Saving Hydrogen Production

Crystalline-to-Amorphous Transformation and Charge Redistribution Induced by Anion–Cation Double Substitution on 3D Ni(OH)₂ Ultrathin Nanosheet Arrays Enable Urea-Assisted Energy-Saving Hydrogen Production

Hydrothermal synthesis of Ni, Co hydroxide nanosheet array on vertically suspended carbon cloth for flexible high-performance supercapacitors

The investigation of Ni(OH)2 electrode materials has been a prominent issue in the field of electrochemical energy. The slow ion diffusion kinetics and inherent low electronic conductivity of Ni(OH)2 restrict its electrochemical performance and application in practice. In this work, mixed-phase nickel-cobalt layered double hydroxide (NiCoLDH) array structures are successfully grown directly on vertically suspended carbon cloth (CC). In contrast to the traditional hydrothermal method, the vertically suspended carbon cloth affordes adequate reaction sites to ensure optimum array structure growth. This unique structure realizes a large mass loading of the active material. Meanwhile, the introduction of flexible electrode substrate carbon cloth effectively enhances the mechanical properties of the electrode. Due to the powerful electrochemistry kinetics, NiCoLDH/CC-1.5 exhibites a great capacitive and excellent rate performance of 1516.5 F g−1 at 1 A g−1 and 1073.75 F g−1 even at 20 A g−1. The assembled asymmetric supercapacitor demonstrates a favorable cycling stability (capacitance retention of 90.11 % after 10,000 cycles at 5 A g−1).

Constructing Fe-Co2P/CeO2 heterostructure nanosheet arrays for attaining energy-saving hydrogen production in seawater

Constructing Fe-Co2P/CeO2 heterostructure nanosheet arrays for attaining energy-saving hydrogen production in seawater

Boosting electrochemical oxygen reduction to hydrogen peroxide coupled with organic oxidation

The electrochemical oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2) is appealing due to its sustainability. However, its efficiency is compromised by the competing 4e− ORR pathway. In this work, we report a hierarchical carbon nanosheet array electrode with a single-atom Ni catalyst synthesized using organic molecule-intercalated layered double hydroxides as precursors. The electrode exhibits excellent 2e− ORR performance under alkaline conditions and achieves H2O2 yield rates of 0.73 mol gcat−1 h−1 in the H-cell and 5.48 mol gcat−1 h−1 in the flow cell, outperforming most reported catalysts. The experimental results show that the Ni atoms selectively adsorb O2, while carbon nanosheets generate reactive hydrogen species, synergistically enhancing H2O2 production. Furthermore, a coupling reaction system integrating the 2e− ORR with ethylene glycol oxidation significantly enhances H2O2 yield rate to 7.30 mol gcat−1 h−1 while producing valuable glycolic acid. Moreover, we convert alkaline electrolyte containing H2O2 directly into the downstream product sodium perborate to reduce the separation cost further. Techno-economic analysis validates the economic viability of this system.

Interfacially Ordered NiCoMoS Nanosheets Arrays on Hierarchical Ti3C2Tx MXene for High-Energy-Density Fiber-Shaped Supercapacitors with Accelerated Pseudocapacitive Kinetics.

Balancing electrochemical activity and structural reversibility of fibrous electrodes with accelerated Faradaic charge transfer kinetics and pseudocapacitive storage are highly crucial for fiber-shaped supercapacitors (FSCs). Herein, we report novel core-shell hierarchical fibers for high-performance FSCs, in which the ordered NiCoMoS nanosheets arrays are chemically anchored on Ti3C2Tx fibers. Beneficial from architecting stable polymetallic sulfide arrays and conductive networks, the NiCoMoS-Ti3C2Tx fiber maintains fast charge transfer, low diffusion and OH- adsorption barrier, and stabilized multi-electronic reaction kinetics of polymetallic sulfide. Consequently, the NiCoMoS-Ti3C2Tx fiber exhibits a large volumetric capacitance (2472.3 F cm-3) and reversible cycling performance (20,000 cycles). In addition, the solid-state symmetric FSCs deliver a high energy density of 50.6 mWh cm-3 and bending stability, which can significantly power electronic devices and offer sensitive detection for dopamine.

In situ fabrication of low-crystallinity (Ni,Fe)xSy nanosheet arrays via room-temperature corrosion engineering toward efficient oxygen evolution

The field of room-temperature corrosion engineering has emerged as a promising avenue for the controlled synthesis of functional nano-materials, owing to its simplicity and potential for scalability. To date, room temperature corrosion engineering has been skillfully applied and successfully used to synthesizee transition metal (oxy)hydroxides. However, the synthesis of transition metal sulfides via room-temperature corrosion encounters challenges due to the low standard electrode potential and sluggish corrosion kinetics of S/Sn2-. Here, we have successfully initiated the oxidation behavior of S22- on Ni3Fe7 foam by adjusting the pH of the aqueous solution (containing (NH4)2SO4 and Na2S2), and subsequently synthesized low-crystallinity (Ni,Fe)xSy nanosheet arrays with significant lattice distortion and amorphous characteristics. Experimental studies combined with theoretical calculations have confirmed Fe within the (Ni,Fe)xSy structure functions as a highly active site while simultaneously expediting the lattice oxygen mechanism, thus yielding a remarkably efficient OER performance.

Tailoring the oxygen evolution reaction activity of lanthanide-doped NiFe-LDHs through lanthanide contraction

Elemental doping is employed to tune the inherent activity and electronic structure of electrocatalysts for water electrolysis. Here, unique nanosheet arrays of NiFe-LDH doped with lanthanide metals (NiFeSm-LDH, NiFeCe-LDH, and NiFeLa-LDH) were developed as high-performance electrocatalysts for oxygen evolution reaction (OER). Notably, NiFeSm-LDH exhibits the superior performance, with the lowest overpotentials of 203 mV (at 10 mA cm−2) for OER. Structural analysis, in-situ Raman spectra and DFT calculations reveal that the high activity of the catalysts can be attributed to synergistic functionalities. Firstly, compared to Ce in NiFeCe-LDH and La in NiFeLa-LDH, Sm element in NiFeSm-LDH can attract more electrons from the outermost 3d orbitals of Ni due to the effect of lanthanide contraction, resulting in the highest valence state and d-band center of Ni. Secondly, the formation of NiOOH phase on NiFeSm-LDH requires a lower overpotential (∼1.32 V) than those on NiFeCe-LDH (1.32 ∼ 1.37 V) and NiFeLa-LDH (∼1.37 V) based on in-situ Raman spectra, which indicate that NiFeSm-LDH has faster kinetics to achieve the Ni(II)-Ni(III) transformation. Thirdly, First-principles simulations reveal that NiFeSm-LDH reduces the formation energy from OOH* to O2 significantly, which eventually improves the catalytic activity. Furthermore, the NiFeSm-LDH||Pt/C couple exhibits a low voltage of 1.59 V at 100 mA cm−2 for overall water splitting.

Multiple strategies regulating the d-band center of Ni2P/NiFe2O4 @N-GTs hierarchical nanoarchitecture as efficient electrocatalyst for overall water splitting

The rational design of highly active electrocatalysts for water electrolysis remains challenging for green hydrogen utilization. Herein, guided by the correlation between the electroactivity and the d-band center (Ed), a novel hierarchical nanoarchitecture (Ni2P/NiFe2O4-VO@N-GTs) was fabricated, in which, Ni2P nanoparticles are grown on the oxygen vacancy-rich NiFe2O4 nanosheet arrays anchoring on N-doping graphene tubes. The results reveal that the multiple strategies including the vacancies and heterogeneous interface construction effectively induce the charge redistribution, and further adjust the Ed to the appropriate energy level, which endows the optimal balance between the adsorption and desorption ability of the catalyst to reaction intermediates, thus leading to the conspicuous electrocatalytic activity. Additionally, the hierarchical nanoarchitecture contributes to the exposure of more active sites, the efficiency of electron transfer, and the release of generated gas. Hence, Ni2P/NiFe2O4-VO@N-GTs presents superior bifunctional activity, especially a low overpotential of 194 mV at 10 mA cm−2 for OER. The corresponding overall water electrolyzer owns a lower cell voltage and long-term durability with continuously operating over 330 h at 100 mA cm−2, outperforming the most reported bifunctional electrocatalysts. This work presents an effective pathway for regulating the Ed through multiple strategies to improve the catalytic performance of catalysts.

Pt-decorated spinel MnCo2O4 nanosheets enable ampere-level hydrazine assisted water electrolysis

Coupling hydrazine oxidation reaction (HzOR) with hydrogen evolution reaction (HER) has been widely concerned for high efficiency of green hydrogen preparation with low energy consumption. However, the lacking of bifunctional electrodes with ampere-level performance severely limits its industrialization. Herein, we put forward an efficient active site anchored strategy for MnCo2O4 nanosheet arrays on nickel foam (NF) by introducing Pt species (denoted as Pt-MnCo2O4/NF), which is standing for excellent bifunctional electrodes. The Pt-MnCo2O4/NF delivers ultralow potentials of −195 mV and 350 mV at 1000 mA cm−2 as well as robust stability for HzOR and HER, respectively. The study of in-situ Raman and reaction kinetics reveal that the formation of key adsorbed *NH2 and *N2H4 intermediates and the rapidly oxidization of intermediates with a fast interfacial charge transfer on Pt-MnCo2O4/NF. Remarkably, the Pt-MnCo2O4/NF assembled two-electrode hydrazine assisted water electrolyzer realizes current density of 100 mA cm−2 and 1000 mA cm−2 at 0.16 V and 0.62 V with over 80 h stability. This work provides a promising way to design efficient electrodes for energy-saving H2 generation under ampere-level current density.

Controlled Synthesis of MoNi4 Ultrathin Nanosheet Arrays as an Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Production

Controlled Synthesis of MoNi₄ Ultrathin Nanosheet Arrays as an Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Production

Multifunctional Wearable Electronic Based on Fabric Modified by PPy/NiCoAl-LDH for Energy Storage, Electromagnetic Interference Shielding, and Photothermal Conversion.

With the rapid advancement of electronic technology, traditional textiles are challenged to keep up with the demands of wearable electronics. It is anticipated that multifunctional textile-based electronics incorporating energy storage, electromagnetic interference (EMI) shielding, and photothermal conversion are expected to alleviate this problem. Herein, a multifunctional cotton fabric with hierarchical array structure (PPy/NiCoAl-LDH/Cotton) is fabricated by the introduction of NiCoAl-layered double hydroxide (NiCoAl-LDH) nanosheet arrays on cotton fibers, followed by polymerization and growth of continuous dense polypyrrole (PPy) conductive layers. The multifunctional cotton fabric shows a high specific areal capacitance of 754.72 mF cm-2 at 5mA cm-2 and maintains a long cycling life (80.95% retention after 1000 cycles). The symmetrical supercapacitor assembled with this fabric achieves an energy density of 20.83µWh cm-2 and a power density of 0.23 mWcm-2. Moreover, the excellent electromagnetic interference shielding (38.83dB), photothermal conversion (70.2 °C at 1000mWcm-2), flexibility and durability are also possess by the multifunctional cotton fabric. Such a multifunctional cotton fabric has great potential for using in new energy, smart electronics, and thermal management applications.

Enhanced water oxidation stability and activity in MnO2 nanosheet arrays through Ti doping

Efficient and sustainable hydrogen production via water electrolysis relies on the utilization of highly active electrocatalysts for the oxygen evolution reaction (OER). Birnessite (δ-MnO2), a type of manganese oxide with a local atomic structure similar to the oxygen-evolving complex in photosystem II, has emerged as a highly promising OER catalyst. Despite considerable efforts have been dedicated to enhancing its activity, the crucial aspect of stability has been often overlooked. Herein, Ti ions have been selectively incorporated into the in-layered lattice of δ-MnO2 nanosheet arrays using a hydrothermal method, aiming to enhance the stability without reducing its activity. The resulting optimal Ti-MnO2 catalyst demonstrates enhanced OER activity in alkaline electrolyte, exhibiting an impressive 85 mV reduction in overpotential at 10 mA cm−2, surpassing the initial MnO2 (495 mV reduced to 410 mV). Remarkably, it shows exceptional durability, with negligible performance decrease observed over the entire 50-hour testing period. It has been demonstrated that the incorporation of Ti serves a dual purpose: it adjusts the electronic structure around Mn, enhancing activity, and simultaneously stabilizes the Mn3+ active sites, resulting in exceptional durability. Furthermore, density functional theory (DFT) calculations provide additional confirmation of the optimized electronic structure of MnO2 achieved through Ti doping, leading to a reduction in the free energy of adsorbed intermediates and expediting the kinetics of the OER process. Our findings open a pathway for enhancing OER stability and activity by doping electrocatalytic inert ions into the lattice of MnO2, applicable not only to Mn-based oxides but also other non-precious metal-based electrocatalysts.

N-doped NiS2 nanosheets array on carbon fiber as an efficient hydrogen evolution reaction electrocatalyst

N-doped NiS2 nanosheets array on carbon fiber as an efficient hydrogen evolution reaction electrocatalyst

Electronic Structure Modification of MnO2 Nanosheet Arrays with Enhanced Water Oxidation Activity and Stability by Nitrogen Plasma.

The strategic design of catalysts for the oxygen evolution reaction (OER) is crucial in tackling the substantial energy demands associated with hydrogen production in electrolytic water splitting. Despite extensive research on birnessite (δ-MnO2) manganese oxides to enhance catalytic activity by modulating Mn3+ species, the ongoing challenge is to simultaneously stabilize Mn3+ while improving overall activity. Herein, oxygen (O) vacancies and nitrogen (N) doping have been simultaneously introduced into the MnO2 through a simple nitrogen plasma approach, resulting in efficient OER performance. The optimized N-MnO2v electrocatalyst exhibits outstanding OER activity in alkaline electrolyte, reducing the overpotential by nearly 160 mV compared to pure pristine MnO2 (from 476 to 312 mV) at 10 mA cm-2, and a small Tafel slope of 89 mV dec-1. Moreover, it demonstrates excellent durability over a 122 h stability test. The introduction of O vacancies and incorporation of N not only fine-tune the electronic structure of MnO2, increasing the Mn3+ content to enhance overall activity, but also play a crucial role in stabilizing Mn3+, thereby leading to exceptional stability over time. Subsequently, density functional theory calculations validate the optimized electronic structure of MnO2 achieved through the two engineering methods, effectively lowering the intermediate adsorption free energy barrier. Our synergistic approach, utilizing nitrogen plasma treatment, opens a pathway to concurrently enhance the activity and stability of OER electrocatalysts, applicable not only to Mn-based but also to other transition metal oxides.

Strong support effect induced by MXene for the synthesis of metal sulfides nanosheet arrays with sulfur vacancies towards selective CO2-to-CO photoreduction

Selective CO2-to-CO photoreduction is under intensive research and requires photocatalysts with tuned microstructures to accelerate the reaction kinetics. Here, we report CuInS2 nanosheet arrays with sulfur vacancies (VS) grown on the two-dimensional (2D) support of Ti3C2Tx MXene for CO2-to-CO photoreduction. Our results reveal that the use of Ti3C2Tx induces strong support effect, which causes the hierarchical nanosheet arrays growth of CuInS2 and simultaneously leads to charge transfer from CuInS2 to Ti3C2Tx support, resulting in VS formed in CuInS2. The strong support effect based on Ti3C2Tx is proven to be applicable to prepare a series of different metal indium sulfide arrays with VS. CuInS2 nanosheet arrays with VS supported on Ti3C2Tx benefit the photocatalytic selective reduction of CO2 to CO, manifesting a remarkable over 14.8-fold activity enhancement compared with pure CuInS2. The experimental and computational investigations pinpoint that VS of CuInS2 resulting from the support effect of Ti3C2Tx lowers the barrier of the rate-limiting step of *COOH → *OH + *CO, which is the key to the photoactivity enhancement. This work demonstrates MXene support effects and offers an effective approach to regulate the atomic microstructure of metal sulfides toward enhancing photocatalytic performance.

Oxygen vacancy-engineered P-doped MoO3/Ce2Mo4O15 bimetallic heterojunction nanosheet array for enhanced oxygen evolution reaction

Surface oxygen vacancies in defective metals have the capacity to enhance oxygen evolution reaction (OER) activity but easily suffer from instability and deactivation in continuous electrocatalysts. Heterojunction engineering is important for achieving effective catalysis, but its simultaneous engineering remains a challenge. Therefore, it is necessary to develop an effective heterojunction catalyst to improve the electrocatalytic stability of defective metallic oxygen vacancies. In this work, we report a Ce, Mo bimetallic defective heterojunction P-MoO3/Ce2Mo4O15@NF-1 via a facile one-step hydrothermal method and annealing in a tube furnace. Bimetallic oxide heterojunctions offer several advantages over conventional single-metal heterojunctions, including stable structure, more active sites, faster rates of electron transfer, and less pollution of the environment. Meanwhile, P-doped catalyst could enhance the metallicity significantly. In addition, the prepared catalyst P-MoO3/Ce2Mo4O15@NF-1 showed extraordinary catalytic activity for OER in alkaline media. The overpotential and Tafel slope of the catalyst at a current density of 50 mA cm-2 were 270 mV and 87.27 mV dec‑1, respectively. It maintains an impressive balance between electrocatalytic activity and stability. This research explores the co-effects of Ce and Mo bimetallic oxide in defective electrocatalysts and also provides ideas for designing OER catalysts with defective metal heterojunctions.