Michel Barsoum

Drexel University | DU · Department of Materials Science and Engineering

The MAX phases are a class of nanolaminated materials composed of an early transition-metal (M), an A-group element (A) and C, N, B and/or P (X). Progress in MAX phase research in recent years has increased their number from the original 50 or so, to more than 300 phases. Since half of the 342 MAX phases have been discovered after 2018, an overview...

Since the discovery of the first MXene, Ti3C2Tz, in 2011, more than 30 new MXene chemistries have been reported. A universal method via which all MXenes can be synthesized is by etching the “A” layer from the MAX phase using hydrofluoric acid, HF. After etching, to delaminate the resulting MXene multilayers, MLs, they are typically treated with a s...

Reactive single-step hot-pressing at 1473 K and 35 MPa for 4 h produces dense, bulk, near single-phase, low-cost, and low-criticality Fe2Al1.15B2 and Fe2Al1.1B2Ge0.05Ga0.05 MAB samples, showing second-order magnetic phase transition with favorable magnetocaloric properties around room temperature. The magnetic as well as the magnetocaloric properti...

Synthesizing high-performance, multifunctional composites often entails poor filler dispersion, complex processes, or limited processing conditions. Hence, the advent of versatile syntheses employing simple conditions, inexpensive fillers, standard equipment, and robust reactions could expand attainable composites having enhanced performance, funct...

Reactive single-step hot-pressing at 1473 K and 35 MPa for 4 h produces dense, bulk, near single-phase, low-cost and low-criticality Fe2Al1.15B2 and Fe2Al1.1B2Ge0.05Ga0.05 MAB samples, showing a second-order magnetic phase transition with favorable magnetocaloric properties around room temperature. The magnetic as well as magnetocaloric properties...

The micromechanism for the deformation of layered crystalline solids (LCSs) such as graphite, mica, and the MAX phases has long been assumed to be basal dislocations alone. The latter, however, cannot explain several important observations made when graphite is deformed such as non-linear elasticity, the stress-strain curves' strong sensitivity to...

Herein the isothermal oxidation of the Mn2AlB2 and Fe2AlB2 MAB phases in air was studied. When oxidized at 700 °C, the weight gain kinetics for Mn2AlB2 are sub-cubic up to 96 h are sub-cubic up to 96 h as a result of the formation of Mn2-xAlxO3 layer. At 800 °C and 900 °C severe spallation of the oxides was observed limiting its service temperature...

Two‐dimensional (2D) MXenes have diverse and chemically tunable optical properties that arise from an interplay between free carriers, interband transitions and plasmon resonances. The nature of photoexcitations and their dynamics in three different members of MXene family, Ti3C2, Mo2Ti2C3, and Nb2C, were investigated using two complementary pump‐p...

This work was inspired by new experimental findings where we discovered a two-dimensional (2D) material comprised of titanium-oxide-based one-dimensional (1D) sub-nanometer filaments. Preliminary results suggest that the 2D material contains considerable amounts of carbon, C, in addition to titanium, Ti, and oxygen, O. The aim of this study is to i...

Aqueous ammonium‐ion batteries (AAIBs) are appealing due to their relatively low cost and good rate performance. In general, AAIBs are environmentally friendlier than their non‐aqueous counterparts. However, it is still a challenge to achieve highly reversible AAIBs with decent voltages and energy/power densities. Herein, we report on a full‐cell c...

We recently reported on the synthesis of one-dimensional (1D) TiO2-based nanofilaments, (NFs) by reacting water insoluble, earth abundant, and non-toxic Ti-containing precursors, such as TiC, TiB2, and TiSi2, among others, with quaternary ammonium hydroxides, mostly tetramethylammonium hydroxide at near-ambient conditions. From selected area diffra...

Treatment of HF or HCl/LiF etched Ti3C2T z with 0.05 M NaHCO3 before water washing reduces the wastewater generated by 75%. When etched with HF, cryolite (Na3AlF6) precipitation from spent etching waste effectively removes fluorine from this waste stream, offers insight into the etching chemistry of MAX to MXene, and provides an effective analytica...

Metal-sulfur battery chemistries have garnered a lot of interest due to their 5-10 fold higher theoretical energy densities compared to state-of-the-art lithium-ion batteries, in addition to the abundance and environmental benignity of sulfur. However, the insulating nature of sulfur, the formation and shuttling of polysulfides, are still major dra...

A simple room‐temperature process of depositing MXene on a III‐V structure with embedded 2D electron gas (2DEG) is used, which results in a large area, 2×104µm2$2 \times {10^4}\mu {m^2}$, photodetector (PD) device that greatly outperforms vacuum deposited Ti/Au metal‐semiconductor‐metal (MSM) PD's. By co‐optimizing properties of 2D MXene contacts a...

The 2D carbides and nitrides, known as MXenes, are among the most recent, but quickly expanding material families. The field is experiencing very fast growth with the number of papers on MXenes roughly doubling every year since their discovery in 2011. Great progress in synthesis and control of MXene properties has been achieved since. Synthesis of...

“High‐performance supercapacitors are important energy storage devices. A facile, inexpensive and scalable technique is developed to obtain the two dimensional (2D), TMA⁺‐MnO2 birnessite flakes by heating Mn3O4 powders for 48 h at 80 °C in an organic hydroxide (tetramethyl ammonium hydroxide) solution. This technique uses earth‐abundant materials a...

The Front Cover illustrates two typical cross‐sectional images of TMA+‐MnO2 and Mo1.33CTz free‐standing films, with highly stacked flakes, exhibiting excellent flexibility and high volumetric capacitances. More information can be found in the Research Article by J. Rosen, M. W. Barsoum and co‐workers.

Practicality of lithium-sulfur batteries is severely hindered by the notorious polysulfide-shuttle phenomenon, leading to rapid capacity fade. This issue is aggravated with increase in sulfur loading, causing low-coulombic efficiency and cycle life. Herein, we present a facile strategy to combine hydrophobic sulfur and hydrophilic , conductive Ti 3...

Synthesis of two-dimensional (2D) materials that is readily scalable, cost-effective, and eco-friendly is important from both scientific and industrial viewpoints. Currently, these 2D materials are synthesized either by selective etching of relatively expensive layered solids, viz. using a top-down approach, or by autoclaving metal salts/organic co...

Room temperature alkali metal - sulfur batteries are promising alternatives to lithium-ion batteries due to their high capacity and low inherent cost. Herein we report MXene (Ti3C2Tx) as a host to confine sulfur (S8) enabling the use of commercialization-friendly carbonate electrolyte in metal-sulfur batteries. The multilayer MXene structure provid...

Aqueous asymmetric supercapacitors (AASCs) can have high voltages and high energy densities. However, the rational design of AASCs with proper negative and positive electrodes remains a challenge. Herein, we report on an AASC using Mo1.33CTz MXene films as the negative electrode, and tetramethylammonium cation intercalated birnessite (TMA⁺‐MnO2) fi...

The atomically laminated Ti2AlC, Ti3AlC2 and Cr2AlC MAX phases, with A = Al, form adherent, passivating α-alumina, Al2O3, oxide scales when heated in air. The effect of solid solutions on the A layers in affecting the oxidation kinetics remains a subject of open research. Herein we synthesize a dense bulk polycrystalline Ti3Al1−xGaxC2 (x ≈ 0.4) sol...

i-MXenes, a new family of 2D transition metal carbides with in-plane ordered vacancies, have shown great potential in aqueous supercapacitor (SC) applications due to their high volumetric capacitances and energy densities. However, how vacancies affect their electrochemical performance, in general, and their self-discharge (SD) behavior in particul...

High-entropy (HE) ceramics, by analogy with HE metallic alloys, are an emerging family of multielemental solid solutions. These materials offer a large compositional space, with a corresponding large range of properties. Here, we report the experimental realization of a 3D HE MAX phase, Ti 1.0 V 0.7 Cr 0.05 Nb 1.0 Ta 1.0 AlC 3 , and a corresponding...

Herein, MoAlB, Fe2AlB2, and Mn2AlB2 with textured microstructures were sinter-forged from pre-reacted preforms in a hot press at 1400, 1200, and 1050 oC, respectively. X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the textured nature and high phase purities. The effect of texturing on the thermoelectric properties was evaluat...

MXene-based aqueous symmetric supercapacitors (SSCs) are attractive due to their environmental nature and good rate performances. However, it remains a challenge to reach voltages over 1.2 V, which significantly diminishes the energy density. Herein, we report on Mo1.33CTz MXene-based SSCs with high voltage in 19.5 M LiCl electrolyte. Benefiting fr...

Degradation of MXenes severely limits the application and industrialization of this large family of two-dimensional (2D) materials. Hydrolysis and oxidation are now considered as two main mechanisms of MXene degradation....

Two-dimensional (2D) materials offer advantages that their 3D counterparts do not. The conventional method for the bulk synthesis of 2D materials has predominantly been through etching layered solids. Herein, we convert – through a bottom-up approach – 10 binary and ternary titanium carbides, nitrides, borides, phosphides, and silicides into 2D fla...

The MAX phases, layered ternary carbides and nitrides, plastically deform via exclusively basal slip systems. This constraint leads to their well-documented plastic anisotropy and deformation mechanisms such as kinking. Basal dislocations govern the incipient plastic deformation, and therefore understanding them is a key step to utilizing the uniqu...

Significant efforts have been dedicated to developing Ti3C2Tz‐based MXene aqueous supercapacitors (SCs) with improved energy and power densities. Notably less research has been devoted to an equally important characteristic of aqueous SCs, viz. self‐discharge (SD). The SD rates are rarely reported despite their crucial importance from a practical p...

MXenes In article number 2103393, Michael Naguib, Michel W. Barsoum, and Yury Gogotsi present a brief historical overview of the first 10 years of MXene research and a perspective on their synthesis and future development. The cover shows a colored SEM image of a multilayer Ti3C2 MXene particle with an accordion-like morphology, which is produced b...

MAX phases and MXenes are important materials that have recently gained great popularity due to their special properties, which render them particularly useful in many applications, including catalytic ones. This can be seen in the large number of publications that appear annually on these materials and their applications. This review aims to evalu...

Recently, we have established that, when loaded in compression, edge-on, atomic layers in layered solid can fail by buckling. The resulting structure is termed a ripplocation. When more than one layer buckles, they outline standing waves with boundaries that we labeled ripplocation boundaries that are nearly fully recoverable. In this paper, we exa...

Since their discovery in 2011, the number of 2D transition metal carbides and nitrides (MXenes) has steadily increased. Currently more than 40 MXene compositions exist. The ultimate number is far greater and in time they may develop into the largest family of 2D materials known. MXenes’ unique properties, such as their metal‐like electrical conduct...

Herein, we synthesize fully dense, bulk, predominantly single-phase, polycrystalline samples of the layered ternary transition metal borides Mn5SiB2 and Fe5SiB2 by reactively hot-pressing Mn, Fe, FeB, Si, and B powders. The atomic structures were imaged using high-resolution scanning transmission electron microscopy (HRSTEM) and revealed high-cryst...

Practicality of lithium-sulfur batteries is severely hindered by the notorious polysulfide-shuttle phenomenon, leading to rapid capacity fade. This issue is aggravated with increase in sulfur loading, causing low-coulombic efficiency and cycle life. Herein, we present a facile strategy to combine hydrophobic sulfur and hydrophilic, conductive Ti3C2...

Lithium-Sulfur batteries are of great interest owing to sulfur's high theoretical capacity, low-cost and environmental benignity. However, the practicality of these batteries has been impeded due to the infamous “polysulfide-shuttle” effect. Although several research articles in the past decade have focused to mitigate this effect, capacity fade an...

Quenching studies of CrB-Al, CrB-Al-B and ß-FeB-Al mixtures revealed that all three undergo a topotactic transformation in the presence of Al to form Cr2AlB2, Cr3AlB4, and Fe2AlB2 MAB phases, respectively. The formation mechanism is intercalation for the Cr-based compounds, and reconstructive for the ß-FeB based mixture.

Efficient water splitting for commercial electrolysis devices is predicated on the development of materials, specifically for the catalytic electrodes, that exhibit an optimal balance between activity and stability. Complicating the development of electrocatalytic materials, particularly for oxygen-evolving anodes in acidic polymer electrolyte memb...

MXenes are a new family of two-dimensional carbides and/or nitrides. Their 2D surfaces are typically terminated by O, OH and/or F atoms. Here we show that Ti3C2Tx-the most studied compound of the MXene family-is a good acid catalyst, thanks to the surface acid functionalities. We demonstrate this by applying Ti3C2Tx in the epoxide ring-opening reac...

MXenes are a relatively new and exciting class of two-dimensional materials, which offer a wide range of compositions and excellent properties including ease of dispersibility and metallic conductivity. These properties render them promising candidates for use as fillers in polymer nanocomposites. Herein, we review how MXene processing methods, the...

How to achieve high mass loadings while maintaining high energy and power densities together with slow self-discharge rates for aqueous asymmetric supercapacitors (AASCs) remains a great challenge. Herein, we tested an AASC using Ti3C2Tz MXene as the negative electrode, a mixture of manganese oxides, Mn3O4 and MnOOH, as the positive electrode with...

Since their discovery in 2011, MXenes have garnered worldwide interest. Given their 2D structure, surface, or termination, chemistries play a vital role in most applications. X-ray photoelectron spectroscopy (XPS) is one of the most common characterization tools for quantifying surface terminations and overall chemistry. Herein, we critically revie...

The MAX phases comprise of a group of layered ternary carbides that exhibit unique mechanical properties which bridge the gap between their metal and ceramic constituents. To study the effects of the global grain orientation, Ti, Si and TiC powders were hot pressed to synthesize highly oriented bulk Ti3SiC2. X-ray diffraction (XRD) was used to veri...

Recently, a new family of MAX phases with in-plane chemical order, i-MAX, have been discovered which incorporate new elements expanding the family of MAX phases. i-MAX phases remain to be synthesized in single-phase bulk form for characterization. Herein, we show that by reactively hot pressing an intermetallic precursor, Y2.23Al, instead of elemen...

Despite the excellent mechanical and electrical performance of MXene-polymer nanocomposites, methods for producing these materials on a larger scale are limited by low-yielding, delaminated, MXene suspensions that are typically employed for their synthesis. Moreover, the hydrophilicity of MXenes restricts the production of well-dispersed nanocompos...

Quaternary MAX phases, (Ta1-xTix)3AlC2 (x = 0.4, 0.62, 0.75, 0.91 or 0.95), have been synthesised via pressureless sintering of TaC, TiC, Ti and Al powders. Via chemical etching of the Al layers, (Ta0.38 Ti0.62)3C2Tz - a new MXene, has also been synthesised. All materials contain an M-layer solid solution of Ta and Ti, with a variable Ta concentrat...

Kinking is a deformation mechanism ubiquitous to layered systems, ranging from the nanometer scale in layered crystalline solids, to the kilometer scale in geological formations. Herein, we demonstrate its origins in the former through multiscale experiments and atomistic simulations. When compressively loaded parallel to their basal planes, layere...

Enhancing both the energy storage and power capabilities of electrochemical capacitors remains a challenge. Herein, Ti3C2T z MXene is mixed with MoO3 nanobelts in various mass ratios and the mixture is used to vacuum filter binder free, open, flexible, and free-standing films. The conductive Ti3C2T z flakes bridge the nanobelts, facilitating elec...

A vacancy-ordered MXene, Mo1.33CTz, from the selective etching of Al and Sc from the parent i-MAX phase (Mo2/3Sc1/3)2AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (Mo2/3Y1/3)2AlC, have not been able to match its forerunner. Herein, we show that the use of...

The MAB phases are a family of layered ternary transition metal borides, with atomically laminated crystal structures comprised of transition metal boride (M-B) layers interleaved by single, or double, Al (A) layers. Herein, density functional theory is implemented to evaluate the thermodynamic stability of disordered (Mn1-xCrx)2AlB2, and disordere...

Terahertz Polarizers In article number 2000084, Lyubov V. Titova and coworkers fabricate terahertz polarizers by simply spin casting two dimensional MXene Ti3C2Tz nanosheets on a photolithographically patterned terahertz‐transparent substrate.

The high theoretical capacitance of molybdenum trioxide (MoO3) renders it an attractive supercapacitor electrode material. However, its low electronic conductivity restricts charge transfer and slows its reaction kinetics. Herein, we vacuum filtered porous, free-standing, flexible and highly conductive films comprised of oxygen vacancy-rich MoO3-x...

MXene is a recently discovered family of two-dimensional transition metal carbides, nitrides and carbonitrides that have shown a lot of promise in the field of energy storage with applications ranging from high capacity anodes for lithium, sodium, potassium and aluminum ion batteries, supercapacitors and catalysts for hydrogen evolution, among seve...

Herein, the fabrication of terahertz (THz) polarizers is reported on by simply spin casting two‐dimensional (2D) MXene Ti3C2Tz nanosheets on a photolithographically patterned THz‐transparent substrate and subsequent immersion in acetone. Lines 30 nm‐thick and 10–20 μm wide result in electric field (E) extinction ratios (ER) of up to 3 dB, or power...