Phase change materials are deceptively simple in concept. When a paraffin wax, a salt hydrate, or a polyethylene glycol melts, it absorbs a large quantity of latent heat at a nearly constant temperature; when it solidifies again, that heat is released. This makes PCMs ideal for banking thermal energy and for passively regulating temperature in buildings, electronics, and batteries. Yet the classic formulations suffer from three chronic weaknesses. First, once molten, they leak, which means they must be contained or encapsulated before they can be deployed. Second, most organic PCMs conduct heat poorly, so charging and discharging the store is slow and temperature gradients build up inside the material. Third, conventional PCMs merely store heat; they do not convert other forms of energy into it, limiting their usefulness in systems that need to harvest sunlight or electricity directly.

MXenes, first reported in 2011 when researchers exfoliated the layered ceramic Ti3AlC2 into two-dimensional titanium carbide sheets, have rapidly become one of the most versatile nanomaterial platforms in materials science. These transition metal carbides and nitrides carry a chemically tunable surface terminated with functional groups, and they combine metallic electrical conductivity with strong in-plane thermal transport. The review emphasizes that this combination is precisely what leaky, sluggish PCMs need. Dispersed or structured within a phase change matrix, MXene nanosheets act simultaneously as a thermal bridge that accelerates heat distribution, an absorbent scaffold that locks the molten PCM in place by capillary forces and surface interactions, and in many designs as the actual energy converter that turns sunlight or electricity into stored heat.

The authors devote considerable attention to how these composites are made, beginning with MXene synthesis itself. The dominant route remains selective etching of the aluminum layers from MAX phase precursors, typically using hydrofluoric acid or gentler fluoride salt mixtures such as hydrochloric acid combined with lithium fluoride, followed by delamination into single-layer sheets. Newer protocols, including electrochemical etching, dry selective extraction guided by computation, and even ultrafast laser synthesis of MAX phases, are expanding the toolkit and reducing the environmental burden of the fluoride chemistry. The review notes that etching conditions directly control the surface terminations, defect density, and flake size of the resulting MXene, which in turn govern how well the nanosheets disperse in a PCM, how strongly they bind the melt, and how efficiently they conduct heat through the composite.

Encapsulation strategies form the second pillar of the review. The simplest approach is the form-stable composite, in which a porous MXene aerogel or hydrogel-derived framework is infiltrated with molten paraffin or polyethylene glycol, producing a monolith that holds its shape even above the melting point. Binderless MXene aerogels assembled without polymeric binders have achieved ultrahigh energy storage densities alongside exceptional electromagnetic interference shielding, a bonus property that stems from the electrical conductivity of the percolating nanosheet network. Hybrid frameworks that pair MXene with graphene or with copper nanowires exploit synergistic conduction pathways, while polymer partners such as polyvinyl alcohol, gelatin, cellulose nanofibers, and polyurethane add mechanical flexibility, producing composite films that can be bent, wrapped around pipes, or integrated into fabrics. Microencapsulation, in which PCM droplets are shelled in silica or polymer with MXene incorporated into the shell or coating, offers another route to leakage-proof, supercooling-suppressed particles suitable for slurries and coatings.

Solar photothermal conversion is where MXene composites deliver their most eye-catching performance. Broad absorption across the solar spectrum, combined with efficient conversion of absorbed photons into heat, allows MXene-loaded PCMs to charge rapidly under illumination. Paraffin infiltrated into Ti3C2Tx MXene and gelatin aerogels, MXene aerogel monoliths, diatomite ceramics coated with MXene, kapok fibers modified with the nanosheets, and composites decorated with gold nanorods or nano copper have all demonstrated high solar-thermal conversion efficiencies and strong shape stability. The review highlights designs that pair MXene with polydopamine for synergistic photothermal enhancement, with biochar from sorghum straw for sustainable scaffolds, and with liquid metal gallium modified on blackbody-inspired principles, extending the concept to interfacial evaporation and desalination where stored heat drives water purification after sunset.

Electrothermal applications form a complementary frontier. Because MXenes conduct electricity, a composite PCM can be charged simply by passing current through it, converting electrical energy into latent heat with near-total efficiency. Flexible films based on polyethylene glycol with two-dimensional MXene, aramid nanofiber composites, cellulose nanofiber materials, and sandwich-structured MXene and polyvinyl alcohol systems with barium sulfate have demonstrated dual-mode solar and electrothermal charging. Such films are candidates for wearable thermal management, defrosting surfaces, and electrically rechargeable heat packs, and the review notes that molecular dynamics studies of lauric acid in polylactic acid and MXene matrices are now providing atomistic insight into how the filler alters crystallization and heat transport.

Perhaps the most consequential application is thermal safety in batteries and electronics. Lithium-ion cells can enter catastrophic thermal runaway when heat accumulates faster than it is removed, and the review cites extensive work on MXene-based composite PCMs for passive battery cooling. Composites pairing MXene with carbon nanotubes, expanded graphite, hexagonal boron nitride nanosheets for electrical insulation, or VO2 for thermally triggered tunable conductivity can absorb heat spikes during fast charging or high discharge, delay the onset of runaway, and in flame-retardant formulations actively suppress fire propagation. Similar composites protect power electronics and LED systems, and some add electromagnetic interference shielding and even radiation protection, turning a simple heat sink into a multifunctional protective layer.

The review closes with a candid assessment of obstacles and a striking glimpse of the future. MXenes are vulnerable to oxidative degradation, which erodes their conductivity over time, and surface and edge passivation strategies are being developed to extend operational lifetimes. Large-scale, low-cost synthesis remains a hurdle, as does the long-term cycling stability of composites exposed to repeated melting. Yet the authors see these materials converging toward integrated platforms that convert, store, and manage energy in a single component: fabrics that harvest sunlight by day, warm the wearer at night, and hide the wearer’s infrared signature; battery packs that cool themselves and shield electronics; and building panels that smooth the intermittency of renewable power. Infrared camouflage, achieved by tuning emissivity and buffering surface temperature with phase change layers, illustrates how far the concept has traveled from simple heat storage. For a field racing to decarbonize, MXene-based composite PCMs, the review concludes, offer a rare combination of high latent heat, fast charging, and multifunctional intelligence that could define the next generation of thermal energy technologies.

Subject of Research: MXene-based composite phase change materials for thermal energy storage and management

Article Title: Review: MXene-based composite phase change materials for preparation, encapsulation, and thermal management

Article References: Wu, Y., Huang, Y., & Li, L. (2026). Review: MXene-based composite phase change materials for preparation, encapsulation, and thermal management. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13844-z

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13844-z

Keywords: MXene, phase change materials, thermal energy storage, encapsulation, photothermal conversion, electrothermal conversion, battery thermal management, infrared camouflage, two-dimensional materials, thermal conductivity, aerogels, renewable energy