MXene Surface Research Articles

(Invited) Tunable Chemistry of 2D Carbide Mxenes for Hydrogen Evolution Reaction

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) are a large family of earth-abundant materials with more than forty compositions synthesized since 2011, such as Ti2CT x , Mo2CT x , Nb2CT x , Ti3C2T x , Mo2TiC2Tx, and Mo2Ti2C3T x . MXenes have emerged as promising candidates for catalytic energy storage and conversion because their 2D surfaces are electrochemically active combined with MXenes’ hydrophilicity, high electrical conductivity, and affinity to bond to molecules and nanomaterials to form hybrid structures. MXenes electrochemical properties can be tuned by the control of multiple variables: in the MXene formula of M n +1X n T x , the transition metals (M) can be any of the groups 4, 5, 6 of the periodic table or their combination, X can be carbon, nitrogen, or a solid solution of both, surface terminations (T x ) can be any of the group 16 and 17, and the ‘n’ (MXene 2D flake thicknesses) can be 1 to 4. In this talk, we will discuss the control of MXene transition metals, their thicknesses, and surfaces to tune their electrocatalytic behavior. Specifically, we present a systematic study of 20 different MXenes, including novel compositions such as W2TiC2T x and Mo2Nb2C3T x and high-entropy MXenes, and discuss how we achieve low overpotential for hydron evolution reaction (as low as ~160 mV).

MXene-Polydopamine-antiCEACAM1 Antibody Complex as a Strategy for Targeted Ablation of Melanoma.

Photothermal therapy (PTT) is a method for eradicating tumor tissues through the use of photothermal materials and photosensitizing agents that absorb light energy from laser sources and convert it into heat, which selectively targets and destroys cancer cells while sparing healthy tissue. MXenes have been intensively investigated as photosensitizing agents for PTT. However, achieving the selectivity of MXenes to the tumor cells remains a challenge. Specific antibodies (Ab) against tumor antigens can achieve homing of the photosensitizing agents toward tumor cells, but their immobilization on MXene received little attention. Here, we offer a strategy for the selective ablation of melanoma cells using MXene-polydopamine-antiCEACAM1 Ab complexes. We coated Ti3C2Tx MXene with polydopamine (PDA), a natural compound that attaches Ab to the MXene surface, followed by conjugation with an anti-CEACAM1 Ab. Our experiments confirm the biocompatibility of the Ti3C2Tx-PDA and Ti3C2Tx-PDA-antiCEACAM1 Ab complexes across various cell types. We also established a protocol for the selective ablation of CEACAM1-positive melanoma cells using near-infrared irradiation. The obtained complexes exhibit high selectivity and efficiency in targeting and eliminating CEACAM1-positive melanoma cells while sparing CEACAM1-negative cells. These results demonstrate the potential of MXene-PDA-Ab complexes for cancer therapy. They underline the critical role of targeted therapies in oncology, offering a promising avenue for the precise and safe treatment of melanoma and possibly other cancers characterized by specific biomarkers. Future research will aim to refine these complexes for clinical use, paving the way for new strategies for cancer treatment.

Contrasting Metallic (Rh0) and Carbidic (2D-Mo2C MXene) Surfaces in Olefin Hydrogenation Provides Insights on the Origin of the Pairwise Hydrogen Addition.

Kinetic studies are vital for gathering mechanistic insights into heterogeneously catalyzed hydrogenation of unsaturated organic compounds (olefins), where the Horiuti-Polanyi mechanism is ubiquitous on metal catalysts. While this mechanism envisions nonpairwise H2 addition due to the rapid scrambling of surface hydride (H*) species, a pairwise H2 addition is experimentally encountered, rationalized here based on density functional theory (DFT) simulations for the ethene (C2H4) hydrogenation catalyzed by two-dimensional (2D) MXene Mo2C(0001) surface and compared to Rh(111) surface. Results show that ethyl (C2H5*) hydrogenation is the rate-determining step (RDS) on Mo2C(0001), yet C2H5* formation is the RDS on Rh(111), which features a higher reaction rate and contribution from pairwise H2 addition compared to 2D-Mo2C(0001). This qualitatively agrees with the experimental results for propene hydrogenation with parahydrogen over 2D-Mo2C1-x MXene and Rh/TiO2. However, DFT results imply that pairwise selectivity should be negligible owing to the facile H* diffusion on both surfaces, not affected by H* nor C2H4* coverages. DFT results also rule out the Eley-Rideal mechanism appreciably contributing to pairwise addition. The measurable contribution of the pairwise hydrogenation pathway operating concurrently with the dominant nonpairwise one is proposed to be due to the dynamic site blocking at higher adsorbate coverages or another mechanism that would drastically limit the diffusion of H* adatoms.

Utilization of recycled materials for low-cost MXene synthesis and fabrication of graphite/MXene composite for enhanced water desalination performance

Access to clean and safe drinking water is essential to human health, economic progress, and ecological stability. Advanced materials have emerged to advance water treatment processes, particularly desalination, but are associated with the major challenge of being fabricated through environmentally taxing mining processes, which contributes to the carbon footprint. This study explores an innovative approach of using a renewable carbon-rich material derived from waste to create MXene nanocomposites that are applied to improve water thermal desalination. The synthesis of MXenes from recycled materials involves a series of chemical and exfoliation procedures, resulting in the production of two-dimensional nanosheets with exceptional electrical and mechanical properties. The integration of biomass offers a sustainable alternative to traditional precursors used for MXene preparation and introduces unique functional groups onto the MXene surface, which enhances its ability to absorb substances. This nanocomposite successfully produced solar evaporation rates of up to 3.0 kg m−2h−1 with 96.03 % solar steam conversion efficiency under single solar irradiation (1 sun). Through extensive characterization of SEM, FESEM, EDX, XRD, BET, contact angle, and performance assessments of desalination and water quality by ICP-OES, this study sheds light on the underlying mechanisms driving the improved water desalination capabilities of MXene composites. The composite materials show great mechanical properties, thermal stability, and chemical stability against acidic, alkali, and concentrated salty conditions. Mechanical robustness is the key advantage of this work. The findings underscore the importance of sustainable material utilization and highlight the potential of MXene composites as next-generation solutions for energy-efficient and environmentally friendly water desalination technologies.

Charge carrier controlled free radical construction efficient photocatalytic self-Fenton system

The photocatalytic self-Fenton technology has demonstrated unique advantages in the low-cost and efficient removal of environmental pollutants. Designing an efficient photocatalytic self-Fenton system (PSFs) to enhance the synergistic effect between photocatalytic H2O2 production and pollutant mineralization processes, as well as understanding the regulatory mechanism of free radical reactions in this process, are crucial for advancing this technology. In this study, an efficient PSFs was developed by coating COFs (TpPa-1) onto the surface of MXene (Ti3C2). Under visible light irradiation, the generation rate of H2O2 reached 983.9 μmol·g−1·h−1, which is 9 times that of pure TpPa-1. Additionally, this led to a significant increase in the removal rate of sulfamethoxazole (SMX) from 25 % to 92 % within 100 min. Photoelectrochemical tests and density functional theory (DFT) calculations confirmed that the incorporation of Ti3C2 not only facilitates efficient charge carrier transport but also enhances the generation of hydroxyl radicals (·OH) and the production of H2O2, thereby improving the photocatalytic self-Fenton removal efficiency of SMX. This research is expected to have a positive impact on the development of efficient PSFs.

Mechanism of the Terahertz Wave-MXene Interaction and Surface/Interface Chemistry of MXene for Terahertz Absorption and Shielding.

ConspectusOver the past two decades, terahertz (THz) technology has undergone rapid development, driven by advancements and the growing demand for THz applications across various scientific and technological domains. As the cornerstone of THz technology, strong THz-matter interactions, especially realized as high THz intrinsic absorption in nanometer-thick materials, play a highly important role in various applications including but not limited to THz absorption/shielding, detection, etc. The rigorous electromagnetic theory has posited a maximum intrinsic absorption of 50% for electromagnetic waves by thin films, and the succinct impedance matching condition has also been formulated to guide the design of highly intrinsically absorbing materials. However, these theories face challenges when applied to the THz spectrum with an ultrabroad bandwidth. Existing thin films typically achieve a maximum intrinsic absorption within a narrow frequency range, significantly limiting the performance of THz absorbers and detectors. To date, both theoretical frameworks and experimental solutions are lacking in overcoming the challenge of achieving broadband maximum intrinsic absorption in the THz regime.In this Account, we describe how two-dimensional (2D) transition-metal carbide and/or nitride (MXene) films with nanometer thickness can realize the maximum intrinsic absorption in the ultrabroad THz band, which successfully addresses the forementioned longstanding issue. Surprisingly, traditional DC impedance matching theory fails to explain this phenomenon, while we instead propose a novel theory of AC impedance matching to provide a satisfactory explanation. By delving into the microscopic transport behavior of free electrons in MXene, we discover that intraflake transport dominates terahertz conductivity under THz wave excitation, while interflake transport primarily dictates DC conductivity. This not only elucidates the significant disparities between DC and AC impedance in MXenes but also underscores the suitability of AC impedance matching for achieving broadband THz absorption limits. Furthermore, we identify a high electron concentration and short relaxation time as crucial factors for achieving broadband maximum absorption in the THz regime. Although approaching the THz intrinsic absorbing limits, it still faces hurdles to the use of MXene in practical applications. First, diverse and uncontrollable terminations exist on the surface of MXene stemming from the synthesis process, which largely influence the electron structure and THz absorbing property of MXene. Second, MXene suffers from poor stability in the presence of oxygen and water. To address the above issues, we have undertaken distinctive works to precisely control the terminations and suppress the oxidation of MXene even at high temperature through surface and interface chemistry, such as low-temperature Lewis basic halide treatment and building a Ti3C2Tx/extracted bentonite (EB) interface. For practical application consideration, we proposed a copolymer-polyacrylic latex (PAL)-based MXene waterborne paint (MWP) with a strong intermolecular polar interaction between MWP and the substrate provided by the cyano group in PAL. This not only has strong THz EMI shielding/absorption efficiency but also can easily adhere to various substrates that are commonly used in the THz band. These studies may have significant implications for future applications of MXene nanofilms in THz optoelectronic devices.

Thermally conductive silver adhesive enhanced by MXene@AgNPs with excellent thermal conductivity for thermal management applications

The Thermal Conductive Silver Adhesive (TCSA) efficiently transfers heat from electronic components to heat dissipation components, preventing overheating and extending device lifespan. Despite the effectiveness of commercial sintered nano TCSA, high production costs necessitate a more affordable, high-performance preparation method. This study presents a strategy for preparing ultra-high thermal conductivity (TC) TCSA using multidimensional thermal conductive fillers and low-temperature sintering of silver nanoparticles (AgNPs). MXene@AgNPs particles are synthesized via in-situ reduction of AgNPs on MXene surfaces. These particles, combined with silver microflakes (AgMFs) as primary fillers and epoxy (EP), undergo low-temperature heat treatment to form the AgMFs-MXene@AgNPs/EP composite. Characterization and computational models show that filler-filler interface thermal resistance (ITRf-f) is critical for TC. Adding MXene alone is insufficient, but using MXene@AgNPs particles as secondary fillers allows AgNPs to interconnect fillers, effectively reducing the ITRf-f. The resulting composite achieves an ultra-high TC of 65.51 Wm−1K−1 with 63 wt% total filler content (60 wt% AgMFs, 3 wt% MXene@AgNPs). This study advances the development of low-cost, high-performance TCSA for thermal management applications.

Enhanced osmotic power generation through anodic electrodeposited MOFs@MXene heterostructured nanochannels

Nanochannel membranes exhibit significant potential in osmotic energy generation, however, achieving an optimal balance between ion selectivity and flux remains challenging. Herein, heterostructured MOFs@MXene nanochannels were prepared via an optimized anodic electrodeposition method, which demonstrated a significant advancement in osmotic energy generation. The unique oriented porous MOFs expanded the interlayer spacing of MXene. The inherent negative charged surface of MXene fostered a synergistic effect that substantially enhanced ion selectivity and flux, achieving a significant diffusion potential of 340.2 mV. These improvements enable the membranes to achieve an impressive power density output of 25.3 W/m2 at a concentration gradient of 106 in KCl and 17.2 W/m2 at a gradient of 500 in NaCl. Furthermore, the membranes demonstrate an energy conversion efficiency of up to 45.1 %. Such structural and functional advancements underscore the potential of these heterostructured nanochannels in robust and efficient osmotic power generation, paving the way for applications in sustainable energy technologies.

Electrochemical Properties of Mo4VC4Tx MXene in Aqueous Electrolytes.

M5C4Tx MXenes represent the most recently discovered and least studied subfamily of out-of-plane ordered double transition metal carbides with 11 atomic layers, probably the thickest of all 2D materials. Molybdenum (Mo) and vanadium (V) in Mo4VC4Tx offer multiple oxidation states, making this MXene potentially attractive for electrochemical energy storage applications. Herein, we evaluated the electrochemical properties of Mo4VC4Tx free-standing thin films in acidic, basic, and neutral aqueous electrolytes and observed the highest gravimetric capacitance of 219 F g-1 at 2 mV s-1 in a 3 M H2SO4. Further, we investigated the intercalation states of four different cations (H+, Li+, Na+, and K+) in MXenes through ab initio molecular dynamics (AIMD) simulation and used density functional theory (DFT) calculations to assess the charge storage mechanisms in different electrolytes. These studies show hydrated Li+, Na+, and K+ ions forming an electric double layer (EDL) at the MXene surface as the primary charge storage mechanism. This work shows the promise of Mo4VC4Tx MXene for energy storage in aqueous electrolytes.

CuxO decorated Ti3C2Tx MXene composites for non-enzymatic glucose sensing with large linear ranges.

Ti3C2Tx MXene/CuxO composites were prepared by acid etching combined with electrochemical technique. The abundant active sites on the surface of MXene greatly increase the loading of CuxO nanoparticles, and the synergistic effect between the different components of the composite can accelerate the oxidation reaction of glucose. The results indicate that at the working potential of 0.55V (vs. Ag/AgCl), the glucose sensor based on Ti3C2Tx MXene/CuxO composite presents large linear concentration ranges from 1 µM to 4.655 mM (sensitivity of 361 µA mM-1 cm-2) and from 5.155 mM to 16.155 mM (sensitivity of 133 µA mM-1 cm-2). The limit of detection is 0.065 µM. In addition, the sensor effectively avoids the oxidative interference of common interfering species such as ascorbic acid, dopamine and uric acid. Thesensor has good reproducibility, stability and acceptable recoveries for the detection of glucose in human sweat sample (97.5-103.3%) with RSD values less than 4%. Based on these excellent properties it has great potential for the detection of glucose in real samples.

Ti─O─C Bonding at 2D Heterointerfaces of 3D Composites for Fast Sodium Ion Storage at High Mass Loading Level.

3D composite electrodes have shown extraordinary promise as high mass loading electrode materials for sodium ion batteries (SIBs). However, they usually show poor rate performance due to the sluggish Na+ kinetics at the heterointerfaces of the composites. Here, a 3D MXene-reduced holey graphene oxide (MXene-RHGO) composite electrode with Ti─O─C bonding at 2D heterointerfaces of MXene and RHGO is developed. Density functional theory (DFT) calculations reveal the built-in electric fields (BIEFs) are enhanced by the formation of bridged interfacial Ti─O─C bonding, that lead to not only faster diffusion of Na+ at the heterointerfaces but also faster adsorption and migration of Na+ on the MXene surfaces. As a result, the 3D composite electrodes show impressive properties for fast Na+ storage. Under high current density of 10mAcm-2, the 3D MXene-RHGO composite electrodes with high mass loading of 10mgcm-2 achieve a strikingly high and stable areal capacity of 3mAhcm-2, which is same as commercial LIBs and greatly exceeds that of most reported SIBs electrode materials. The work shows that rationally designed bonding at the heterointerfaces represents an effective strategy for promoting high mass loading 3D composites electrode materials forward toward practical SIBs applications.

In situ fabrication of 2D Ti3C2/1T&2H-MoS2/TiO2 photocatalyst for sulfamethazine degradation

Sunlight-driven photocatalysis is a very appealing approach for solving the current energy crisis because it will not cause secondary pollution. Titanium dioxide (TiO2) has attracted much attention in the field of photocatalysis due to its simple preparation, environmental friendliness and easy modification. However, reducing the band gap and expanding the light absorption range to reduce the carrier recombination rate of TiO2 is still a huge challenge. Herein, we report a two-dimensional (2D) Ti3C2/1 T&2 H-MoS2/TiO2 photocatalyst obtained by in situ growth of a 1 T&2 H-MoS2/TiO2 Z-scheme heterojunction on a highly conductive Ti3C2 MXene surface. The spectral response range of the resulting Ti3C2/1 T&2 H-MoS2/TiO2 (Ti3C2:1 T&2 H-MoS2:TiO2= 1:10:10) photocatalyst was broadened to 696 nm and the band gap was reduced to 1.83 eV, which was responsible for the strong light-harvesting capacity and improved charge separation. The activity of the Ti3C2/1 T&2 H-MoS2/TiO2 photocatalyst was evaluated by photocatalytic degradation of sulfamethazine (SMZ). The degradation rate of SMZ reached 99.8 % after 90 min of illumination. These results demonstrate that the combination of Ti3C2 MXene and heterojunction is a feasible strategy to enhance the light-harvesting capacity and charge transport in photocatalytic reaction.

Synergistic barium titanate/MXene composite as a high-performance piezo-photocatalyst for efficient dye degradation

Piezo-photocatalysis combines photocatalysis and piezoelectric effects to enhance catalytic efficiency by creating an internal electric field in the photocatalyst, improving carrier separation and overall performance. This study presents a high-performance piezo-photocatalyst for efficient dye degradation using a synergistic barium titanate (BTO)-MXene composite. The composite was synthesized via a facile method, combining the unique properties of BTO nanoparticles with the high conductivity of MXene. The structural and morphological analysis confirmed the successful formation of the composite, with well-dispersed BTO nanoparticles on the MXene surface. The piezo-photocatalytic activity of the composite was evaluated using a typical dye solution (Rhodamine B: RhB) under ultraviolet irradiation and mechanical agitation. The results revealed a remarkable enhancement in dye degradation (90 % in 15 min for piezo-photocatalysis) compared to individual stimuli (58.2 % for photocatalysis and 95.8 % in 90 min for piezocatalysis), highlighting the synergistic effects between BTO and MXene. The enhanced catalytic performance was attributed to the efficient charge separation and transfer facilitated by the composite’s structure, leading to increased reactive species generation and dye molecule degradation. Furthermore, the composite exhibited excellent stability and reusability, showcasing its potential for practical applications in wastewater treatment. Overall, this work represents a promising strategy for designing high-performance synergistic catalysts, addressing the pressing need for sustainable solutions in environmental remediation.

A first-principles study of the lithium storage properties of transition metal doped TM-Ti2CO2 (TM=Sc, V, Cr, Mn, Fe, Co, Ni and Cu)

Two-dimensional transition metal carbides, known as MXenes, have garnered significant interest for their potential applications in lithium-ion batteries anode materials, owing to their distinctive properties. Doping, a prevalent method for material modification, involves the substitution of metal atoms within MXenes with other elements to modulate material properties. Given that MXenes inherently contain transition metals, doping with additional transition metals presents an optimal approach for enhancing their performance. In this study, we investigated the effect of doping eight transition metals (Sc, V, Cr, Mn, Fe, Co, Ni, Cu) onto Ti2CO2, aiming to elucidate their impact on the lithium storage properties of the material. Our findings reveal that the introduction of different dopant atoms induces changes in the d-band center of the material, consequently influencing the adsorption energy of lithium ions on the MXene surface in a nearly linear fashion. What’s more, doping with Sc, Cr, and Mn atoms results in an elevation of the migration energy, while doping with Fe, Co, Ni, and Cu atoms leads to a notable increase in the open circuit voltage (OCV). Remarkably, only V atom doping demonstrates an optimal combination of suitable adsorption energy, OCV (0.66 V), and minimal diffusion energy (0.11 eV). These results underscore the significance of transition metal doping in tailoring the lithium storage properties of MXene-based anode materials, offering insights for the design and optimization of next-generation lithium-ion batteries.

Optimization of Synthesizing Conditions for MXene (Ti3C2) Photocatalyst: Effect of LiF:Ti3AlC2 Mass Ratio

The analysis of the proposed work, specifically the development of the MXene photocatalyst, will be described in this chapter. The results of the analysis are useful for comparing the pristine precursor and etched structures of the MXene photocatalyst. A minimally intensive layer delamination (MILD) method will be used to create the MXene photocatalyst which uses lower fluorine content solution (HCl-LiF) creating a safer and easier method. The synthesis parameters for the development of highly efficient MXene photocatalysts, such as LiF:Ti3AlC2 mass ratio will be optimized. FTIR, XRD, SAP, FESEM and DR UV-Vis analysis will be used to characterize the as-developed MXene photocatalyst and its precursor, Ti3AlC2. The hypothesis of this study is etching treatment will increase the hydrophilicity and active functional group such as oxygen (O), fluorine (F) and hydroxyl (-OH) on MXene surfaces. The performance of photocatalytic degradation will be tested with an initial dye concentration of 30 ppm, solution pH at pH7 at room temperature (±27 ̊C). Each photocatalytic degradation study was performed in 50 ml of methylene blue solution with 0.1 g photocatalyst. All developed MXenes will undergo photocatalytic degradation performance to identify the optimized synthesizing conditions. The highest MXene photodegradation performance was found to reach 90% removal within 180 min.

3D MXene/PVA Aerogel Enabling a Dendrite-Free Zn Metal Anode.

Aqueous zinc-ion batteries have attracted widespread attention due to their low cost and high safety. Unfortunately, their commercial applications are greatly inhibited by the negative effects of zinc dendrites and side reactions. A solution that utilizes a 3D host can help mitigate these issues. In this paper, we present a 3D host that is composed of an aerogel scaffold with a poly(vinyl alcohol) and MXene structure. The embedded Zn can be densely packed inside the host due to its zincophilic properties. During cycling, the fluorine-based functional groups on the surface of MXene were able to react with the electrolyte to form the ZnF2 solid electrolyte interphase, which can effectively protect the composite anode. As a result, the symmetrical battery was capable of stable cycling for >300 h at a high current density of 10 mA cm-2. More impressively, the assembled full cell retained 93.86% after 800 cycles at a current density of 5 A g-1. This work provides an effective idea for improving the cycling performance of aqueous zinc-ion batteries.

Single‐Atom Catalysts Based on the Mo2CO2 MXene for CO Oxidation

AbstractThrough density functional theory calculations, the mechanism of CO oxidation to CO2 on single‐atom catalysts consisting of an atom of Ti, Fe, or Zn deposited on the surface of the Mo2CO2 MXene is investigated. In the case of Fe@Mo2CO2, a mechanism resembling that of Termolecular Langmuir–Hinshelwood (TLH) is thermodynamically and kinetically favored, displaying very exothermic CO2 formation, low activation energies, and easy CO2 desorption. On Ti@Mo2CO2, the dissociation of CO2 is almost barrierless and much more likely to occur than CO2 desorption, barring the usage of this surface as a catalyst for CO oxidation. Finally, on Zn@Mo2CO2, a hybrid Langmuir–Hinshelwood/Eley–Rideal (LH/ER) mechanism is thermodynamically and kinetically feasible. Here, after the first CO2 forms, with an energy barrier of only 0.62 eV, the second CO2 is formed spontaneously, and the Zn–CO2 interactions are weak enough to allow desorption. The calculated thermodynamic quantities and reaction rates at T = 300 K indicate that Fe@Mo2CO2 should be quite active toward CO oxidation, followed by Zn@Mo2CO2, while the Ti‐based model is inactive. The results add to the evidence that establishes single transition metal atoms adsorbed on MXene surfaces as cheap and easily obtainable catalysts that offer the best of both bare and functionalized MXenes.

Modulation of Charge Redistribution in Heterogeneous CoSe-Ni0.95Se Coupling with Ti3C2Tx MXene for Hydrazine-Assisted Water Splitting.

Integrating abundant dual sites of hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER) into one catalyst is extremely urgent toward energy-saving H2 production. Herein, CoSe-Ni0.95Se heterostructure coupling with Ti3C2Tx MXene (CoSe-Ni0.95Se/MXene) is fabricated on nickel foam (NF) to enhance the catalytic performance. The heterogeneous CoSe-Ni0.95Se and MXene coupling effect can change the coordination of Ni and Co, resulting in adjusted interfacial electronic field and enhanced electron transfer from Ni0.95Se to CoSe especially near MXene surface. Also, the appearance of MXene can anchor more active sites, thereby abundant nucleophilic CoSe and electrophilic Ni0.95Se are formed induced by the charge redistribution, which can tailor d-band center, moderate *H adsorption free energy (∆GH *) and facilitate adsorption/desorption for hydrazine intermediates, contributing to much enhanced HER and HzOR performance. For example, the low potentials of -160.8 and 116.1mV at 400 mA cm-2 are seen for HER and HzOR with long-term stability of 7 days. When assembled as overall hydrazine splitting (OHzS), a small cell voltage of 0.35V to drive 100 mA cm-2 is obtained. Such concept of integrating abundant nucleophilic and electrophilic dual sites and regulating their d-band centers can offer in-depth understandings to design efficient bifunctional HER and HzOR electrocatalysts.

Cu/Cu2O/C nanoparticles and MXene based composite for non-enzymatic glucose sensors

Copper/Cuprous oxide/Carbon nanoparticles decorated MXene composite was prepared and subsequently examined for its potential application as a non-enzymatic glucose sensor. To carry out this, initially the Cu MOF/MXene composite was synthesised by the hydrothermal method and was annealed in an unreacted environment at different time intervals. During this process, petal like Cu MOF on MXene loses the organic ligands to form a Cu/Cu2O/C based nanoparticles on MXene. Further, an electrode was fabricated with the developed material for understanding the sensing performance by cyclic voltammetry and chronoamperometry in 0.1 M NaOH solution. Results reveal that the highest weight percentage of copper oxide in the composite (15 min of annealed material) shows a higher electro catalytic activity for sensing glucose molecules due to more active sites with good electron transfer ability in the composite. The formed composite exhibits a wide linear range of 0.001–26.5 mM, with a sensitivity of 762.53 μAmM−1cm−2 (0.001–10.1 mM), and 397.18 μAmM−1cm−2 (11.2–26.9 mM) and the limit of detection was 0.103 μM. In addition to this, the prepared electrode shows a good reusability, repeatability, selectivity with other interferences, stability (93.65% after 30 days of storage), and feasibility of measuring glucose in real samples. This finding reveals that the metal oxide derived from MOF based nanoparticle on the MXene surface will promote the use of non-enzymatic glucose sensors.

Construction of MXene-based flame retardant with multiple carbonization towards for reducing fire hazard and smoke release of epoxy resin

MXene is a promising flame retardant for composites. Currently, how to construct modified MXene nanomaterials with high flame-retardant efficiency is a challenge. In this work, a functionalized MXene-based flame retardant (MXene-AP-Cu) was synthesized by grafting phytic acid copper complex onto the surface of MXene, and was utilized to prepare high performance epoxy resin (EP) composites. Only 2 wt% MXene-AP-Cu increased limited oxygen index (LOI) of EP to 29.7% from 21%, with an enhancement of 41.4%. In addition, EP/2% MXene-AP-Cu presented excellent suppression effect on the release of heat, smoke and CO, as reflected by a 40%, 18%, 25.3% and 33.3% decreases in peak of heat release rate (PHRR), total heat release (THR), total smoke product (TSP) and peak of CO release rate, respectively, compared to EP. The multiple carbonization of MXene-AP-Cu, including lamellar barrier effect, catalytic carbonization of MXene and copper irons, dehydration and carbonization of phytic acid, contributed to better flame retardancy. Besides, the impact strength of EP/MXene-AP-Cu was increased to a certain extent, compared to EP.