Nanosheet Architecture Research Articles

Effect of Polymer Type Additives in Selective Wet Etching of Si1-XGex- to Si-Film to Enhance Etch Rate Selectivity

To extend the scalability of the logic transistor beyond the 3-nm process, the architecture of the metal-oxide-semiconductor field-effect transistor (MOSFET) has changed from FinFET to gate-all-around FET (GAAFET). In addition, to continue the scaling of MOSFET further, various concepts of nanosheet architecture devices, including GAAFET, Forksheet FET, and Complementary FET, have been vigorously researched. To fabricate nanosheet devices, releasing Si channels via selective etching of Si1-xGex- to Si-layer is a key process. However, during the selective etching of Si1-xGex- to Si-layer, simultaneous etching of Si- with Si1-xGex-layer is inevitable. Therefore, protecting the Si-layer while selective etching of the Si1-xGex-layer is a major challenge to acquire uniform channel layers (i.e., Si-layers). In this study, to protect the Si-layer during the selective wet etching of Si1-xGex- to Si-film, we came up with an idea based on the concept of selective chemisorption of polymers on Si- rather on Si1-xGex-film. Functional groups of polymers can chemisorb onto the Si surface, followed by building the hindrance layer that prohibits the etching of Si-film. Thus, we tested the effect of polymer type additives in selective wet etching of Si1-xGex- to Si-film depending on the functional groups (carboxylic group, amine group, alcohol group, etc.) and the molecular weight. To characterize the etching amount of the Si-film during the selective wet etching of Si1-xGex- to Si-film, the wet etching of epitaxially grown 3-periods of Si1-xGex/Si multilayer on Si substrate was performed followed by high-resolution transmission electron microscopy (HR-TEM) analysis. When using a specific type of polymer additive during wet etching, the etching amount of Si-film was >0.5 nm within 2 minutes, while that using without any additive was ~0.8 nm within 2 minutes, indicating that polymer type additive can produce the hindrance layer successfully onto Si-film preventing the etching of Si-film. The HR-TEM images depending on polymer types and mechanism of protecting Si-film during the selective wet etching of Si1-xGex- to Si-film will be presented in detail. Acknowledgement This work was supported by the Technology Innovation Program (20022475, Development of wet Etchant capable of high selection etching in microprocesses below 10 nm) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) References [1] Lee, Seung-Jae, et al. "Extremely high selective Si1−xGex-film wet etchant generating highly dissolved oxygen via peracetic acid oxidant for lateral gate-all-around FETs with a logic node of less than 3-nm." Chemical Engineering Journal 475 (2023): 146257.

Facile construction of multifunctional Cu2O@ZnIn2S4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of tetracycline (TC) under visible light irradiation, DFT calculations

The extensive applicability and remarkable stability of nano-semiconductor photocatalysts are of paramount importance for advancing the field of efficient water treatment. This study presents, Cu2O@ZnIn2S4 photocatalytic materials with type II heterostructure were prepared by indium zinc sulfide capping technology to degrade tetracycline. Characterization results indicated that the degradation rate of tetracycline hydrochloride (TC) could achieve 99.2 % under simulated aqueous environmental conditions, maintaining a degradation rate exceeding 85 % after five cyclic stability tests. Concurrently, the constructed type-II heterojunction effectively enhanced the transient photo responsiveness of the catalyst, facilitating the rapid transfer of photogenerated electrons. Furthermore, the structural configuration of the parceled ZnIn2S4 lamellae acted as a photon trap, minimizing the reflection of incident light and augmenting light utilization efficiency. The inherent electric field of the heterojunction significantly facilitated the degradation of TC, while the nanosheet architecture and surface porosity of the catalyst contributed to enhanced mass transfer capabilities, as corroborated by density-functional theory calculations and band gap analysis. This study utilized Cu2O@ZnIn2S4 as an efficient photocatalyst for water treatment, thereby offering a viable approach for practical applications of the catalyst.

Anion‐Mediated Rapid and Direct Synthesis of FeNiOOH for Robust Water Oxidation

AbstractFeNiOOH is regarded as the most stable active species in the oxygen evolution reaction (OER), but the high oxidation energy of NiOOH poses a challenge to directly synthesize FeNiOOH as a real OER catalyst. Herein, an anion‐mediated kinetically controlled strategy is proposed, coupled with cation‐induced geometric topology modulation, to directly synthesis FeNiOOH with ultra‐thin, densely packed nanosheet architectures. Specifically, the Cl−‐mediated in situ generation of hypochlorous acid promotes the direct formation of NiFeOOH. Concurrently, high‐valence competitive Ru3+ mitigate electrostatic repulsion, fostering a compact and densely packed assembly of Ru/FeNiOOH nanosheet branches. Furthermore, the intrinsic electron‐capturing ability of FeOOH, in synergy with the stabilizing effect of doped Ru atoms, further promote the formation and stabilization high‐valence NiOOH. Consequently, the hierarchical Ru/FeNiOOH@NiPOx nanoarray catalyst displays exceptional OER performance, with an overpotential of 172 mV at 10 mA cm−2 and outstanding stability. This study provides a novel strategy to directly construct a real catalyst.

Enhancing the charge storage capacity of ultrathin metal–organic framework nanosheets with CO2-derived carbon nanotubes

Metal-organic frameworks (MOFs) hold promise as efficient electrode materials for supercapacitors, but their practical application is hindered by the intrinsic low electrical conductivity. Here, we employ CO2-derived carbon nanotubes based on molten salt electrolysis (MSE-CNTs) as the framework to guide the growth of nickel-based MOF (Ni-MOF). The resulting MSE-CNTs/Ni-MOF composite exhibits an impressive specific capacitance of 1714.2 F g−1 at 1 A g−1, 1.45 and 1.26 times greater than bare Ni-MOF (1185.7 F g−1) and CVD-CNTs/Ni-MOF (1364.3 F g−1, the composite of Ni-MOF and commercial CNTs produced by chemical-vapor-deposition), respectively. Moreover, the assembled hybrid supercapacitor (MSE-CNTs/Ni-MOF//active carbon) achieves a remarkable specific capacitance of 136.5 F g−1 at 1 A g−1 and an energy density of 54.8 Wh kg−1 at 850 W kg−1, standing among the best of the state-of-the-art. The superior capacitive performance of MSE-CNTs/Ni-MOF than CVD-CNTs/Ni-MOF can be attributed to the better electrical conductivity of MSE-CNTs, the thinner nanosheet architecture of MSE-CNTs/Ni-MOF, and the effective electrically conductive network within the composite. This work marks a paradigm shift from greenhouse gas CO2 to excellent energy storage materials, paving the way for addressing both the energy and climate issues simultaneously.

Achieving Complete Conversion from Nickel Foam to Nickel Sulfide Foam for a Freestanding Hybrid‐Supercapacitor Electrode

AbstractWe present a unique, one‐step, hydrothermal process to prepare nickel sulfide (Ni3S2) foam by a simple and direct conversion from nickel foam, which contributes both as a scaffold for the reaction and as reactant. The Ni3S2 foam exhibits remarkable mechanical stability, retaining the structural integrity of the foam and excellent crystallinity even after ultrasonication at 200 W for 30 mins. We document the transformation of the nickel foam template into a Ni3S2 foam, highlighting the role of synthesis duration on the phase evolution and unique morphology of Ni3S2. PXRD and SEM analyses reveal a complete transformation after 24 hours from the nickel foam to a pure Ni3S2 foam, which has a highly porous and interconnected ultra‐thin nanosheet architecture. This significantly enhances the surface area and provides many electrochemical reaction sites. In a three‐electrode cell, the capacity of the Ni3S2 foam electrode is 3.9 C cm−2 at 8 mA cm−2, which is higher than previous reports for Ni3S2. In a hybrid supercapacitor device, the Ni3S2 foam demonstrates significant increase in capacitance through 500 cycles and the capacitance plateaus after 2000 cycles. Even after 8500 continued charge‐discharge cycles, the device exhibits excellent cycle stability indicating improvement with age.

2D Differential Metallic Immunopotentiators Drive High Diversity and Capability of Antigen-specific Immunity Against Tumor.

The therapeutic efficacy of vaccines for treating cancers in clinics remains limited. Here, a rationally designed cancer vaccine by placing immunogenically differential and clinically approved aluminum (Al)or manganese (Mn) in a 2D nanosheet (NS) architecture together with antigens is reported. Structurally optimal NS with a high molar ratio of Mn to Al (MANS-H) features distinctive immune modulation, markedly promoting the influx of heterogeneous innate immune cells at the injection site. Stimulation of multiple subsets of dendritic cells (DCs) significantly increases the levels, subtypes, and functionalities of antigen-specific T cells. MANS-H demonstrates even greater effectiveness in the production of antigen-specific antibodies than the commercial adjuvant (Alhydrogel) by priming T helper (Th)2 cells rather than T follicular helper (Tfh) cells. Beyond humoral immunity, MANS-H evokes high frequencies of antigen-specific Th1 and CD8+ cell immunity, which are comparable with Quil-A that is widely used in veterinary vaccines. Immunized mice with MANS-H adjuvanted vaccines exert strong potency in tumor regression by promoting effector T cells infiltrating at tumor and overcoming tumor resistance in multiple highly aggressive tumor models. The engineered immunogen with an intriguing NS architecture and safe immunopotentiators offers the next clinical advance in cancer immunotherapy.

CuO@N/C-ZnO nanoflowers with quantum dots derived from ZIF-8 for efficient CO2 photoreduction

In this pioneering work, an innovative photocatalyst, denoted as the porous erythrocytic-like nanoflower derived from zeolitic imidazolate framework (ZIF-8) (CuO@N/C-ZnONF), has been meticulously crafted. This design integrates a porous nanosheet of nitrogen and carbon co-doped ZnO, strategically refined with CuO nanosheets (CuONS) architecture originating from ZIF-8. This innovative nanomaterial serves as a nanoreactor for converting CO2 into CO and CH4. The distinctive porous nanoflower structure facilitates enhanced mobility of charge carriers throughout the accessible framework, maximizes exposure of active sites, and improves the flow of charge carriers while preventing their recombination. Additionally, the porous characteristics facilitate the diffusion of reactants and products. The synthesized 10CuO/N-C-ZnONF demonstrates superior photocatalytic performance, yielding high CO and CH4 outputs of 286.16 and 39.74 µmol g−1h−1, respectively, and exhibits excellent long-term stability.

Directionally Exfoliated Ni/Co Hydroxide-Organic Framework Nanosheets for Enhanced Wearable Glucose Sensing.

We report two-dimensional (2D) Ni/Co-based metal hydroxide-organic framework nanosheets (Ni/Co-MHOF NSs) for the construction of an efficient electrochemical nonenzymatic glucose sensor. The nanosheet architecture maximizes the exposure of coordinatively unsaturated metal sites, which enables a largely improved electrocatalytic performance toward the glucose oxidation reaction. The as-designed nonenzymatic sensor exhibits a high sensitivity of 235.71 μA·mM-1·cm-2 and a wide linear range of 1-3000 μM. The sensor presents excellent selectivity against several potential interferences and a short response time of 3.0 s. Of interest, a high-performance flexible sensor is developed by depositing the Ni/Co-MHOF NSs on screen-printed electrodes, which reveal decent bending stability. The designed glucose sensor patch can attach to the human body and realize noninvasive glucose monitoring in human sweat. This work may shed light on the application of novel MHOFs in the field of wearable electrochemical sensing.

Rational Construction of Bi2CuO12Se4 and VGCFs@Fe2O3 Composite Electrodes for High-Performance Semi-Solid-State Asymmetric Supercapacitors.

Recently, supercapacitors (SCs) are extensively explored as effective energy storage devices. Specifically, asymmetric SCs are being developed to enhance energy density using suitable materials with favorable nanostructures. This study describes the construction of a bismuth copper selenite (BCS-200) working electrode with an ultrathin nanosheet(UTNS) architecture. This morphology is achieved using a low-cost electrodeposition (ED) method, followed by annealing. The impact of ED time on the development of morphology is studied by synthesizing comparative electrodes simultaneously. The optimized BCS-200 electrode prepared with a deposition time of 200 s shows higher specific capacity/capacitance (Cs/Csc) values of 330.9 mAh g-1/2206.6 F g-1 than the other synthesized electrodes (BCS-100, BCS-150, BCS-250, and BCS-300). Besides, a vapor-grown carbon fiber (VGCF)-added Fe2O3 composite coated on nickel foam (NF) is developed as a negative electrode. The VGCFs@Fe2O3/NF electrode exhibits the (Cs/Csc) values of 183.5 mAh g-1/734.4 F g-1, which is associated with ultra-high cycling stability. In addition, the fabricated BCS-200 and VGCFs@Fe2O3/NF electrodes are combined to construct a wearable semi-solid-state asymmetric SC (SSASC) with an energy density (Ed) of 20.5Wh kg-1 and a cycling stability of 91.7% over 40000 charge/discharge cycles. Furthermore, the real-time applicability of the SSASC is verified by powering it in practical applications.

Ultrathin 2D metal-organic framework nanosheet arrays to boost the overall efficiency of water splitting

Developing cost-effective and highly efficient electrocatalysts for water splitting has posed a significant challenge in recent research. This work presents a facile approach to synthesizing a 2D nickel-based metal-organic framework (TIT-1) using 2,3,5,6-tetracarboxyphenylpyrimidine (TCPP), 4,4′-bipyridine (BPY) and nickel nitrate hexahydrate under solvothermal conditions. The detailed structure and phase purity were characterized by X-ray analysis, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). To enhance the water electrolysis ability, the TIT-1 nanosheet (TIT-1@NS/NF) was fabricated via ultrasonic treatment of pure TIT-1 for 30 min. The TIT-1@NS/NF electrode was synthesized via an in-situ growth method and employed as an electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at ambient temperature. The results indicate that TIT-1@NS/NF achieved a current density of 10 mA cm−2 at an overpotential of 196 mV for OER and 270 mV for HER under the same conditions, so exhibiting superior performance compared to TIT-1. The electrochemical durability of TIT-1@NS/NF showed a retention rate of 87% for OER and 90% for HER. The superior electrocatalytic performance is primarily attribute to the synergistic impact of the 2D nanosheet architecture, which significantly increased the specific surface area and facilitated enhances electronic conductivity. The presence of partially deprotonated carboxylate groups and open metal sites (OMS) in TIT-1 further boosts the enhanced activity, as they exposed a multitude of unsaturated metal sites, thereby optimizing both the OER and HER process. Additionally, an asymmetric electrolytic cell comprising TIT-1@NS/NF was designed and assembled to assess its effectiveness for overall water splitting in alkaline conditions.

Ligand-Induced Electronic Structure Modulation of Self-Evolved Ni3S2 Nanosheets for the Electrocatalytic Oxygen Evolution Reaction.

Modulating the electronic structure of the electrocatalyst plays a vital role in boosting the electrocatalytic performance of the oxygen evolution reaction (OER). In this work, we introduced a one-step solvothermal method to fabricate 1,1-ferrocene dicarboxylic acid (FcDA)-decorated self-evolved nickel sulfide (Ni3S2) nanosheet arrays on a nickel foam (NF) framework (denoted as FcDA-Ni3S2/NF). Benefiting from the interconnected ultrathin nanosheet architecture, ligand dopants induced and facilitated in situ structural reconstruction, and the FcDA-decorated Ni3S2 (FcDA-Ni3S2/NF) outperformed its singly doped and undoped counterparts in terms of OER activity. The optimized FcDA-Ni3S2/NF self-supported electrode presents a remarkably low overpotential of 268 mV to achieve a current density of 10 mA cm-2 for the OER and demonstrates robust electrochemical stability for 48 h in a 1.0 M KOH electrolyte. More importantly, in situ electrochemical Raman spectroscopy reveals the generation of catalytically active oxyhydroxide species (NiOOH) derived from the surface construction during the OER of pristine FcDA-Ni3S2/NF, contributing significantly to its superior electrocatalytic performance. This study concerns the modulation of electronic structure through ligand engineering and may provide profound insight into the design of cost-efficient OER electrocatalysts.

Construction of BiOCl/bismuth-based halide perovskite heterojunctions derived from the metal-organic framework CAU-17 for effective photocatalytic degradation

The designed synthesis of an S-scheme heterojunction has possessed a great potential for improving photocatalytic wastewater treatment by demonstrating increased the photoredox capacity and improved the charge separation efficiency. Here, we introduce the fabrication of a heterojunction-based photocatalyst comprising bismuth oxychloride (BiOCl) and bismuth-based halide perovskite (BHP) nanosheets, derived from metal-organic frameworks (MOFs). Our composite photocatalyst is synthesized through a one-pot solvothermal strategy, where a halogenation process is applied to a bismuth-based metal-organic framework (CAU-17) as the precursor for bismuth sourcing. As a result, the rod-like structure of CAU-17 transforms into well-defined plate and nanosheet architectures after 4 and 8 h of solvothermal treatment, respectively. The modulation of the solvothermal reaction time facilitates the establishment of an S-scheme heterojunction, resulting in an increase in the photocatalytic degradation efficiency of rhodamine B (RhB) and sulfamethoxazole (SMX). The optimized BiOCl/BHP composite exhibits superior RhB and SMX degradation rates, achieving 99.8% degradation of RhB in 60 min and 75.1% degradation of SMX in 300 min. Also, the optimized BiOCl/BHP composite (CAU-17-st-8h sample) exhibited the highest rate constant (k = 3.48 × 10−3 min−1), nearly 6 times higher than that of the bare BHP in the photocatalytic degradation process of SMX. The enhanced photocatalytic efficiency can be endorsed to various factors: (i) the in-situ formation of two-components BiOCl/BHP photocatalyst, derived from CAU-17, effectively suppresses the aggregation of pristine BHP and BiOCl particles; (ii) the S-scheme heterostructure establishes a closely-knit interfacial connection, thereby facilitating efficient pathways for charge separation/transfer; and (iii) the BiOCl/BHP heterostructure enhances its capacity to absorb visible light. Our investigation establishes an effective strategy for constructing heterostructured photocatalysts, offering significant potential for application in photocatalytic wastewater treatment.

A novel nanosheet reconfigurable field effect transistor with dual-doped source/drain

—In this paper, a reconfigurable field-effect transistor (RFET) with dual-doped nanosheet architecture and triple independent gates is proposed and studied with the numerical simulations. The proposed RFET can behave as either an n/p-type MOSFET or an n/p-type tunneling-FET (TFET) according to different program biases. A comprehensive study is carried out on the device mechanism and the influence of key device parameters. Various metrics, such as the on-state current (ION), off-state current (IOFF), ION/IOFF, threshold voltage (VT) and sub-threshold swing (SS), are used to evaluate the proposed RFET. This RFET combining the advantages of the conventional MOSFETs (High ION and operation speed) and the new emerging TFETs (Low IOFF, sub-threshold swing and power dissipation) could make the circuit design more flexible and high efficiency, and improve the circuit performance.

Boosting the catalytic activity toward oxygen reduction via a heterostructure of porous iron oxide-decorated 2D NiO/NG nanosheets

As a noble metal substitute, two-dimensional (2D) hierarchical nano-frame structures have attracted great interest as candidate catalysts due to their remarkable advantages – high intrinsic activity, high electron mobility, and straightforward surface functionalization. Therefore, they may replace Pt-based catalysts in oxygen reduction reaction (ORR) applications. Herein, a simple method is developed to design hierarchical nano-frame structures assembled via 2D NiO and N-doped graphene (NG) nanosheets. This procedure can yield nanostructures that satisfy the criteria correlated with improved electrocatalytic performance, such as large surface area, numerous undercoordinated atoms, and high defect densities. Further, porous NG nanosheet architectures, featuring NiO nanosheets densely coordinated with accessible holey Fe2O3 moieties, can enhance mesoporosity and balance hydrophilicity. Such improvements can facilitate charge transport and expose formerly inaccessible reaction sites, maximizing active site density utilization. Density functional theory (DFT) calculations reveal favored O2 adsorption and dissociation on Fe2O3 hybrid structures when supported by 2D NiO and NG nanomaterials, given 2D materials donated charge to Fe2O3 active sites. Our systematic studies reveal that synergistic contributions are responsible for enriching the catalytic activity of Fe2O3@NiO/NG in alkaline media – encompassing internal voids and pores, unique hierarchical support structures, and concentrated N-dopant and bimetallic atomic interactions. Ultimately, this work expands the toolbox for designing and synthesizing highly efficient 2D/2D shelled functional nanomaterials with transition metals, endeavoring to benefit energy conversion and related ORR applications.

CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes.

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm-2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg-1 at a power density of 330.5 W kg-1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.

Transforming zirconium-porphyrin frameworks into 2D nanosheet-assembled architectures for enhanced carbon dioxide capture

Developing advanced sorbents for selective carbon dioxide (CO2) sequestration with minimal energy consumption remains a pivotal challenge. This study presents a novel strategy through transforming 3D bulk zirconium-porphyrin frameworks into the corresponding 2D nanosheet-assembled superstructures for enhanced CO2 capture. The hierarchical frameworks with well-organized nanosheet architectures exhibit significantly increased specific surface area from 600 m2/g to 2400 m2/g while providing kinetic benefits for gas diffusion. Compared to the adsorption behavior of the bulk counterparts, the nanosheet-assembled frameworks demonstrate a 1.5-fold increase in CO2 adsorption capacity without compromising CO2/N2 selectivity. Theoretical calculation reveals that the coordination unsaturated Zr-O clusters, electron delocalized environments both in interlayer gaps and micropores provided binding sites for CO2 capture. Our research demonstrates an adaptable structure-directed approach for the crystal engineering of metal-organic frameworks which would inspire the creation of state-of-the-art crystalline porous materials for broadened applications.

3D Dense Encapsulated Architecture of 2D Bi Nanosheets Enabling Potassium-Ion Storage with Superior Volumetric and Areal Capacities.

2D alloy-based anodes show promise in potassium-ion batteries (PIBs). Nevertheless, their low tap density and huge volume expansion cause insufficient volumetric capacity and cycling stability. Herein, a 3D highly dense encapsulated architecture of 2D-Bi nanosheets (HD-Bi@G) with conducive elastic networks and 3D compact encapsulation structure of 2D nano-sheets are developed. As expected, HD-Bi@G anode exhibits a considerable volumetric capacity of 1032.2 mAh cm-3, stable long-life span with 75% retention after 2000 cycles, superior rate capability of 271.0 mAh g-1 at 104 C, and high areal capacity of 7.94 mAh cm-2 (loading: 24.2mg cm-2) in PIBs. The superior volumetric and areal performance mechanisms are revealed through systematic kinetic investigations, ex situ characterization techniques, and theorical calculation. The 3D high-conductivity elastic network with dense encapsulated 2D-Bi architecture effectively relieves the volume expansion and pulverization of Bi nanosheets, maintains internal 2D structure with fast kinetics, and overcome sluggish ionic/electronic diffusion obstacle of ultra-thick, dense electrodes. The uniquely encapsulated 2D-nanosheet structure greatly reduces K+ diffusion energy barrier and accelerates K+ diffusion kinetics. These findings validate a feasible approach to fabricate 3D dense encapsulated architectures of 2D-alloy nanosheets with conductive elastic networks, enabling the design of ultra-thick, dense electrodes for high-volumetric-energy-density energy storage.

Salt Effect Engineering Single Fe-N2P2-Cl Sites on Interlinked Porous Carbon Nanosheets for Superior Oxygen Reduction Reaction and Zn-Air Batteries.

Developing efficient metal-nitrogen-carbon (M-N-C) single-atom catalysts for oxygen reduction reaction (ORR) is significant for the widespread implementation of Zn-air batteries, while the synergic design of the matrix microstructure and coordination environment of metal centers remains challenges. Herein, a novel salt effect-induced strategy is proposed to engineer N and P coordinated atomically dispersed Fe atoms with extra-axial Cl on interlinked porous carbon nanosheets, achieving a superior single-atom Fe catalyst (denoted as Fe-NP-Cl-C) for ORR and Zn-air batteries. The hierarchical porous nanosheet architecture can provide rapid mass/electron transfer channels and facilitate the exposure of active sites. Experiments and density functional theory (DFT) calculations reveal the distinctive Fe-N2P2-Cl active sites afford significantly reduced energy barriers and promoted reaction kinetics for ORR. Consequently, the Fe-NP-Cl-C catalyst exhibits distinguished ORR performance with a half-wave potential (E1/2) of 0.92V and excellent stability. Remarkably, the assembled Zn-air battery based on Fe-NP-Cl-C delivers an extremely high peak power density of 260mWcm-2 and a large specific capacity of 812mAhg-1, outperforming the commercial Pt/C and most reported congeneric catalysts. This study offers a new perspective on structural optimization and coordination engineering of single-atom catalysts for efficient oxygen electrocatalysis and energy conversion devices.

Designed nickel–cobalt-based bimetallic oxide slender nanosheets for efficient urea electrocatalytic oxidation

The efficient development of electrocatalysts is a critical necessity in constructing urea-splitting systems that enable the production of environmentally friendly and renewable fuels. Achieving this objective entails optimizing the composition and structure of the electrocatalytic materials. Here, a straightforward synthetic strategy has been employed for designing Ni–Co bimetallic oxide with slender nanosheets architecture. Specifically, Ni–Co layered double hydroxide nanosheets are synthesized through a hydrothermal treatment, followed by the conversion of these Ni–Co-based precursors into Ni–Co bimetallic oxide slender nanosheets using a calcination method. The density of states indicates that Ni–Co bimetallic oxide can greatly enhance the conductivity compared with a single NiO for the UOR. Moreover, owing to the synergistic effect of the compositions and the unique advantages offered by the nanosheet architecture, the resulting electrocatalyst demonstrates improved performance in terms of overall urea splitting. Specifically, the Ni–Co bimetallic oxide delivers a low overpotential of 79 mV at 10 mA cm−2 with a small Tafel slope of 45.1 mV dec−1 and exhibits long-term durability even after extensive testing.

F-regulated Ni2P-F3 nanosheets as efficient electrocatalysts for full-water-splitting and urea oxidation.

Heteroatomic anion doping represents a powerful approach for manipulating the electronic configuration of the active metal locus in electrocatalysts, resulting in enhanced multifunctional electrocatalytic properties in hydrogen/oxygen evolution reactions (HER/OER). Here, fluorine-tailored Ni2P-F3 nanosheets were synthesized and evaluated as a robust multifunctional electrocatalyst for HER, OER, and UOR. Our comprehensive experimental and theoretical investigations reveal that the anionic F effectively tailored the electronic states of the Ni2P-F3 nanosheets, resulting in an elevated d-band center and optimizing the sorption capacity of intermediates. In addition to thermodynamically and kinetically favoured redox reactions, F doping facilitates the reconstruction and generation of active γ-NiOOH. Resulting from the optimized electronic configuration and nanosheet architecture, outstanding catalytic activities are demonstrated by Ni2P-F3 with low overpotentials to reach 100 mA cm-2 for HER (177 mV) and OER (293 mV), surpassing Ni2P by 234 and 205 mV, respectively. Notably, 1.618 V is required for full-water-diversion to reach 10 mA cm-2, while 1.414 V is required with urea oxidation for 100 mA cm-2.