Capacitors, catalysts and coatings: MXenes drive industrial innovations

MXenes, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as transformative materials since their discovery in 2011. MXenes possess a rare combination of properties that distinguish them from other 2D materials: metallic conductivity paired with hydrophilicity, solution processability at room temperature, and tunable surface chemistry. They offer electrical conductivity like metals, mechanical flexibility like polymers, and hydrophilic surfaces that can be chemically tuned. Few materials provide this level of multifunctionality, which is why MXenes have gained such intense research attention in just over a decade.

MXenes are characterized by the general formula M_n+1X_nT_x where M represents transition metals, X denotes carbon or nitrogen, n = 1-3, and Tx indicates surface terminations such as -O, -OH, -F, or -Cl. There are more than 30 known MXene compositions already, and computational predictions suggest thousands more are possible. Researchers can modify their surface terminations to adjust conductivity, stability, catalytic activity, and ion transport properties. This tunability gives MXenes a huge design advantage over other 2D materials, such as graphene or transition metal dichalcogenides, and positions them as powerful candidates for customized, task-specific technologies.

For example, MXenes can be dispersed in water, modified with diverse surface groups, and integrated into composites through simple mixing, which makes them uniquely accessible for multifunctional applications spanning energy storage, catalysis, electronics, and environmental remediation. We analyzed the CAS Content Collection^TM, the largest human-curated repository of scientific information, to better understand how these materials are being used across various industries and applications. We found that journal and patent publications showed significant growth in the past decade (2015-2026), with patents accounting for 22% of publications (see Figure 1):

Figure 1: Number of journal and patent publications for MXenes. Inset shows the percentage share of journals and patents. *2026 data is partial through January. Source: CAS Content Collection.

[H2]: MXene applications encompass the energy transition, biomedical devices, and more

How are MXenes moving from the lab to common usage? To answer that question, we analyzed the occurrence of MXenes in the CAS Lexicon, a specialized search function within CAS SciFinderⓇ, to identify concepts in publications. These concepts can include applications, properties, substance classes, and synthesis methods. We began by identifying application concepts for MXenes and grouping them under broader application areas (see Figure 2).

Figure 2: Applications of MXenes identified from CAS Lexicon concepts. Level 1 nodes present the applications and the number of publications. Level 2 nodes show the concepts grouped under the applications. Their size is proportional to the number of publications. Nodes are color-coded according to the percentage of patents. Source: CAS Content Collection.

[Breaker]: For researchers new to conceptual searching or those wanting to refine their search strategies, CAS offers training videos covering basic workflows including structure-based queries, reaction searching, and refining results by property data. 

Energy storage is the most researched application due to MXenes' role in battery anodes and supercapacitors, which reflects their exceptional volumetric capacitance and excellent rate capabilities. Notably, the technology has evolved beyond traditional lithium-ion systems to include sodium-ion, lithium-sulfur, and emerging zinc-ion batteries.

MXenes' unique combination of metallic conductivity and processability makes them ideal for next-generation electromagnetic shielding in electronics, telecommunications, and aerospace applications. Catalysis applications span electrochemical catalysts, photocatalysts, and specialized hydrogen evolution reaction catalysts. This diversity underscores MXenes' tunable surface chemistry and their effectiveness as standalone catalysts and conductive supports for active species.

Several applications exhibit exceptionally high patent-to-journal ratios. Coatings lead with 48% patent coverage, particularly anticorrosive coatings and general coating materials. MXenes' barrier properties, mechanical flexibility, and multifunctionality drive their application in coatings. MXene-enhanced textiles (43% patents) offer integrated sensing, heating, and antibacterial properties, while MXene-based membranes (39% patents) excel in water desalination and purification applications. Fireproofing applications (37% patents) benefit from MXenes' thermal stability and barrier effects.

Sensors represent a rapidly growing field with diverse implementations including biosensors, gas sensors, and wearable sensors. The moderate patent intensity suggests an earlier-stage market, though pressure and strain sensors show higher commercial activity. Biomedical applications span antibacterial agents, photothermal therapy, and wound healing. The high patent coverage for photothermal agents (26%) indicates strong commercial interest in cancer treatment applications. 

[H2]: The role of MXenes in the research landscape

Individual substances and substance class ‘Concepts’ indexed in the CAS Content Collection are assigned ‘Roles’ based on the nature of the studies involving the indexed substance. We used these CAS-indexed roles to understand the exact type of studies involving the MXenes (see Figure 3). 

Figure 3: Analysis of the nature of studies using MXenes based on CAS assigned ‘Roles’. Level 1 nodes show the prevalent ‘Roles’ and the number of publications. Level 2 nodes show the relevant CAS Lexicon ‘Concepts’ in publications where MXenes play the specified ‘Roles’.

This analysis reveals the multifaceted roles that MXenes play, spanning from fundamental property characterization to advanced technical applications. By further leveraging the CAS Lexicon ‘Concepts,’ we identified more specific details of the most prominent ‘Roles’ associated with the MXenes:

• Technical and engineering materials: MXenes predominantly serve as active materials, with composites representing the largest application category. Researchers extensively incorporate MXenes into nanocomposites and films, leveraging their two-dimensional structure for creating multifunctional materials. The significant focus on nanostructured materials and semiconductor heterojunctions highlights MXenes' role in next-generation electronics and optoelectronics. Notably, electromagnetic shields and energy storage systems represent major technical applications, while the research on aerogels demonstrates interest in three-dimensional MXene architectures for lightweight, high-performance applications.

• Properties: Understanding MXene properties remains a leading research priority because surface terminations and morphology are critical to determining MXene performance. Electric conductivity and surface area represent fundamental characteristics that enable MXenes' success in energy storage and catalysis. The emphasis on microstructure, electrochemical properties, and impedance reflects the material's prominence in electrochemical applications. Studies of electron transfer, adsorption, and binding energy provide mechanistic insights crucial for rational material design. The focus on current density and pore size distribution relates to optimizing performance in batteries, supercapacitors, and catalytic systems.

• Nanomaterials: MXenes predominantly exist as nanosheets, reflecting their inherent two-dimensional nature following delamination from MAX phases. The substantial research on MXene-based nanocomposites demonstrates strategies for combining MXenes with complementary materials to enhance functionality. Studies on nanostructured materials indicate efforts to create hierarchical architectures beyond simple nanosheets.

• Synthetic preparation: Etching remains the dominant synthesis approach. This primarily involves selective removal of A-layers from MAX phases using HF or in-situ HF methods. The presence of hydrothermal reaction as a synthesis method reflects ongoing efforts to develop alternative, potentially safer, and more environmentally friendly synthesis routes, though this represents a smaller fraction compared to conventional etching techniques.

• Physical and engineering processes: MXenes undergo various processes with energy storage, highlighting their role in charge storage mechanisms within batteries and supercapacitors through ion intercalation and surface redox reactions.

• Modifier and additive: Beyond serving as primary active materials, MXenes function effectively as modifiers, particularly in electromagnetic shields and nanocomposites. Their incorporation into hydrogels expands applications into biomedical and soft materials domains. The significant research on fire-resistant materials and fireproofing agents demonstrates MXenes' protective capabilities, leveraging their thermal stability and barrier properties.

• Catalyst: The hydrogen evolution reaction represents a major catalytic application, positioning MXenes as promising materials for sustainable hydrogen production and water splitting technologies.

The prevalence of composite materials such as nanocomposites, hydrogels, aerogels, films, and nanostructured materials highlights the merits and limitations of MXenes. MXenes excel as multifunctional enhancers but require composite architectures for optimal performance. Their metallic conductivity, hydrophilicity, and solution processability enable seamless integration into diverse matrices — polymers, oxides, carbons — that address common MXene limitations like mechanical fragility and oxidation susceptibility. Including MXenes in these matrices leverages their unique properties unavailable in conventional materials through synergistic combinations.

[H2]: The most prevalent MXene substances

As noted, there are over 30 currently known MXene compositions with the possibility of hundreds more. We examined the patent percentage of the 30 most common, and found that titanium carbide (Ti₃C₂) overwhelmingly dominates MXene research (see Figure 4).

Figure 4: Top 30 most prevalent MXenes and the distribution of patent and journal publications. Source: CAS Content Collection.

The concentration of patents with titanium carbide reflects Ti₃C₂'s accessible synthesis from Ti₃AlC₂, excellent conductivity, and versatile applications. Beyond Ti₃C₂, research diversifies into early transition metal carbides with dramatically higher patent intensities: Ti₂C, V₂C, and Nb₂C show strong commercial interest despite smaller publication volumes. 

Higher-order MXenes like Ta₄C₃ and niobium titanium carbide (NbTiC) exhibit exceptional patent-to-publication ratios, indicating early-stage but high-value innovations. Notably, surface-terminated variants of Ti₃C₂-including oxide, hydroxide, fluoride, and chloride forms collectively represent substantial research with variable patent coverage. Oxide-terminated MXenes consistently show minimal patent activity (0-2%), possibly indicating fundamental research focus, while carbonitride and multi-metal MXenes demonstrate elevated commercial interest, highlighting their potential for property tuning through compositional engineering.

[H2]: Understanding specific MXene types

Individual MXene substances are indexed in the CAS Registry® and include detailed information such as substance names, CAS numbers, molecular formula, and ‘Roles,’ as previously discussed. We identified specific types of MXenes in the CAS Registry and classified them by key parameters to gain a better understanding of the various types:

[H3]: MXenes classified by stoichiometry

MXene stoichiometry significantly influences application focus, as evidenced by publication distribution (see Figure 5). M₃X₂(n=2) dominates the literature, reflecting its superior stability and ease of synthesis compared to M₂X(n=1) and M₄X₃(n=3), and it showed the highest growth in the last three years.

Figure 5: MXenes grouped by their stoichiometry. (A) Number of publications and percentage of patents; (B) Publication trends; (C) Distribution of the individual MXene groups in applications. Source: CAS Content Collection.

Energy storage leads all stoichiometries but shows varying preference with layer thickness of individual MXene layers: M₂X, M₄X₃, and M₃X₂. Thicker MXenes (M₄X₃) provide more interlayer galleries for ion intercalation, enhancing battery capacity. Conversely, M₂X's higher energy storage focus reflects fewer competing applications.

Catalysis favors M₂X over M₃X₂ and M₄X₃, as thinner structures offer higher surface-area-to-volume ratios and more exposed active edge sites for catalytic reactions. The larger surface area of M₂X facilitates electron transfer and reactant accessibility.  Electromagnetic shielding strongly favors M₃X₂ (11%) due to optimal balance between conductivity and processability. M₂X's lower representation suggests insufficient shielding effectiveness from single-layer structures.

M₄X₃'s distinctive strength in coatings stems from superior mechanical properties and thickness, providing better barrier protection. The rarity of M₄X₃ publications reflects challenging synthesis, requiring precise MAX phase etching control. The high percentage of patents in M₄X₃ can be attributed to its usage in patent-heavy applications such as energy storage, coatings, and membranes.

[H3]: MXenes classified by transition metals

Titanium-based MXenes overwhelmingly dominate the field, primarily due to Ti₃C₂Tₓ's accessible synthesis from commercially available Ti₃AlC₂ MAX phases, excellent stability, and well-characterized properties. Ti MXenes show balanced application distribution, serving as the versatile "workhorse" across all fields (see Figure 6). 

Figure 6: MXenes grouped by their transition metals. (A) Number of publications and percentage of patents; (B) Publication trends; (C) Distribution of the individual MXene groups in applications. Source: CAS Content Collection.

Catalytic activity correlates strongly with metal identity. Mo and W MXenes exhibit exceptional catalytic focus, attributed to their optimal hydrogen binding energies and multiple oxidation states favoring hydrogen evolution reactions. Mo-Ti double-metal MXenes achieve the highest catalytic representation, demonstrating synergistic effects from combining metals with different electronic structures.

Energy storage preferences vary systematically: V (60%) and Sc (57%) MXenes show the highest focus, reflecting their multiple accessible oxidation states enabling pseudocapacitive charge storage. Group V metals (V, Nb, Ta) consistently show 49-60% energy storage focus due to favorable redox activity and ionic intercalation properties.

Early transition metals (Sc, Y, Zr, Hf) receive less attention due to challenging MAX phase synthesis and higher reactivity. However, Hf and Zr MXenes show strong catalytic applications benefiting from high work functions and unique electronic structures. The scarcity of W and Y publications reflects difficult synthesis and limited MAX phase precursor availability, despite their promising catalytic performance.

[H3]: MXenes classified by anions

MXene research is overwhelmingly dominated by carbide-based compositions (97% of publications), while nitrides and carbonitrides remain relatively underexplored. This disparity reflects the synthetic accessibility of carbide MXenes, particularly Ti₃C₂Tₓ, which forms readily through selective etching of MAX phases. Carbides and nitrides show high growth in the last three years (see Figure 7).

Figure 7: MXenes grouped by their anions. (A) Number of publications and percentage of patents; (B) Publication trends; (C) Distribution of the individual MXene groups in applications. Source: CAS Content Collection.

Application patterns reveal distinct anion-dependent preferences. Energy storage dominates across all types, with nitrides showing the highest focus, likely due to their superior electronic conductivity and enhanced lithium-ion diffusion kinetics compared to carbides. Nitride MXenes also demonstrate exceptional catalytic activity, attributed to their optimal d-band center positioning and nitrogen-induced electronic modifications that enhance surface reactivity.  

Carbonitrides occupy a unique middle ground, showing balanced performance across energy storage  and electromagnetic shielding. Carbide MXenes exhibit the broadest application diversity, including significant representation in sensors, electromagnetic shielding, and biomedical applications, reflecting their versatile surface chemistry, hydrophilicity, and established functionalization protocols. The limited nitride research suggests substantial untapped potential in emerging applications.

[H3]: MXenes classified by surface terminations

Surface terminations in MXenes are functional groups that bind to the transition metal surface during the etching of MAX phases. These critically influence MXene properties and application suitability, as evidenced by distinct research patterns (see Figure 8). 

Figure 8: MXenes grouped by their surface terminations. (A) Number of publications and percentage of patents; (B) Publication trends; (C) Distribution of the individual MXene groups in applications. Source: CAS Content Collection.

Oxygen-terminated MXenes dominate the literature and demonstrate the highest catalytic activity among all terminations. This reflects oxygen's ability to create active redox sites and optimal binding energies for reaction intermediates, which are particularly beneficial for electrocatalysis and photocatalysis.  

Fluorine terminations show enhanced electrochemical stability and hydrophobic characteristics, making them preferred for energy storage where cycling stability is crucial. The strong C-F bonds resist oxidation and prolongs operational lifetime. Hydroxyl groups confer superior hydrophilicity and solution processability, enabling diverse applications across sensors and remediation. Their hydrogen-bonding capability facilitates interlayer spacing control and functional molecule anchoring.  

Notably, chlorine and sulfur terminations exhibit the highest energy storage focus, attributed to their weaker electronegativity compared to oxygen/fluorine, which enhances ion intercalation kinetics and pseudocapacitive behavior. However, their synthetic challenges and lower stability limit broader exploration and represent significant opportunities for emerging research in high-performance energy storage systems.

[H2]: What’s next in MXene innovation

With their high-performance properties and unique tunability, MXenes offer a level of versatility that few material families can match. They’re conductive, flexible, and can be dissolved in water, and researchers are using them in applications ranging from EV components and batteries to conductive inks and specialized membranes.

MXene research shows that substances are diversifying beyond Ti₃C₂ dominance. Emerging compositions, particularly double-transition-metal, M4X3(n=3),  carbonitride, and alternative-termination MXenes, are increasingly prevalent in patent-heavy applications despite limited publication numbers. This pattern signals potential commercial breakthroughs in specialized applications including electromagnetic shielding, advanced coatings, textiles, and next-generation energy storage. 

Future growth will likely emphasize scalable synthesis methods, long-term stability solutions, and application-specific compositional engineering to translate the laboratory promise of MXenes into industrial reality.

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