Graphene’s isolation in 2004 did not merely produce a new material. It established that atomically thin crystals could exist as free-standing sheets at all, which opened a family of materials now numbering in the hundreds.
For anyone specifying materials, this matters practically. Several of graphene’s weaknesses — no bandgap, electrically conductive when you may need an insulator, chemically inert when you may need reactivity — are precisely the strengths of other 2D materials. Choosing correctly starts with knowing what else exists.
Hexagonal Boron Nitride: The Insulating Twin
h-BN has the same honeycomb lattice as graphene, with alternating boron and nitrogen atoms in place of carbon. The geometry is nearly identical; the electronic behaviour is opposite.
Where graphene is a semimetal with no bandgap, h-BN is a wide-bandgap insulator. Where graphene absorbs light strongly across the spectrum, h-BN is transparent. And where graphene conducts heat exceptionally well, so does h-BN — one of the few properties they share.
That combination makes h-BN valuable in exactly the situations where graphene’s conductivity is a problem:
- Thermally conductive but electrically insulating fillers. This is a genuinely large commercial market. Electronics packaging, thermal interface materials, and encapsulants frequently require heat removal without electrical pathways. Graphene cannot serve this need; h-BN can, and does, commercially today.
- Dielectric substrates and gate dielectrics in 2D electronics. Graphene on silicon dioxide performs poorly because the oxide surface has charge traps and roughness. Graphene on h-BN performs dramatically better, and this stacking is standard practice in device research.
- High-temperature lubrication. h-BN retains lubricity in oxidizing environments and at temperatures where graphite fails, because it does not oxidize the way carbon does.
h-BN is sometimes called “white graphene,” which captures the visual difference and understates the functional one.
MXenes: Conductive, Hydrophilic, and Reactive
MXenes are a family of transition metal carbides and nitrides, first reported from Drexel University in 2011. They are produced by selectively etching the A layer out of a layered MAX phase precursor, leaving stacked sheets of transition metal carbide with surface terminations — oxygen, hydroxyl, and fluorine groups — inherited from the etchant.
Titanium carbide, Ti₃C₂Tₓ, is the most studied member.
MXenes are interesting because they combine properties graphene has to be engineered into having:
- Metallic conductivity together with hydrophilicity. MXenes disperse in water without surfactants or oxidation, because their surface terminations are polar. Graphene must be oxidized to achieve water dispersibility, and oxidation destroys its conductivity. This is a fundamental advantage for solution processing.
- High volumetric capacitance. Because MXenes are denser than graphene and store charge through both double-layer and pseudocapacitive mechanisms, their volumetric energy storage performance is strong — addressing exactly the volumetric weakness discussed in our supercapacitor article.
- Excellent EMI shielding. Thin MXene films achieve shielding effectiveness competitive with metal foils, a result that has attracted substantial commercial interest.
- Tunable chemistry. Dozens of compositions with different transition metals and terminations give a compositional design space graphene does not have.
The limitations are real. MXenes oxidize in water and air over days to weeks, which is a serious shelf-life problem still being addressed through storage chemistry and surface passivation. Synthesis typically uses hydrofluoric acid or fluoride salts, which brings handling and waste considerations. And production volumes remain far below graphene’s, with correspondingly high prices and limited supply chains.
Transition Metal Dichalcogenides: The Semiconductors
MoS₂, WS₂, WSe₂ and related compounds are the semiconducting members of the 2D family. A monolayer of MoS₂ has a direct bandgap in the region of 1.8 eV, which is precisely what graphene lacks.
That bandgap enables what graphene cannot do:
- Transistors with a real off state. Graphene transistors cannot be switched off effectively because there is no gap, which is the fundamental obstacle to graphene digital logic. TMD transistors switch properly.
- Photodetectors and light emitters operating in the visible range, with strong light-matter interaction for such thin material.
- Valleytronics and spintronics, exploiting properties that arise from the broken symmetry of the monolayer structure.
Separately, MoS₂ and WS₂ have long histories as solid lubricants, well predating the 2D materials field. That application is mature, commercial, and largely independent of the recent research interest.
The limitations are carrier mobility well below graphene’s, sensitivity to defects and substrate interactions, and — as with all these materials — the difficulty of producing large-area films with uniform layer number.
Others Worth Knowing
Black phosphorus (phosphorene) has a thickness-tunable bandgap and high mobility, making it electronically attractive. It also degrades rapidly in air, which has confined it largely to encapsulated research devices.
Layered double hydroxides and clays are the cheap, mature end of the layered materials family, produced at industrial scale for a fraction of the price of any of the above. For barrier and rheological applications, they remain the default and often the correct choice — our sister site Nanoclay Guide covers them in detail.
Silicene, germanene, and stanene are elemental analogues of graphene with theoretically interesting properties and severe stability problems.
A Selection Guide
| Requirement | Best fit | Why |
|---|---|---|
| Electrical conductivity, low cost | Graphene | Cheapest conductive 2D material at scale |
| Thermal conduction, electrical insulation | h-BN | Wide bandgap with high thermal conductivity |
| Water-processable conductive films | MXene | Conductive and hydrophilic simultaneously |
| Volumetric energy storage | MXene | Higher density, pseudocapacitive contribution |
| EMI shielding, thin films | MXene or graphene | Both strong; MXene better per unit thickness |
| Digital logic transistors | TMD | Has a usable bandgap |
| Visible-range optoelectronics | TMD | Direct bandgap at monolayer thickness |
| Mechanical reinforcement | Graphene | Highest in-plane strength and modulus |
| Gas barrier, low cost | Nanoclay | Adequate performance at commodity price |
| High-temperature lubrication | h-BN or MoS₂ | Oxidation resistance |
The Practical Point
Graphene is the best-known 2D material, the cheapest, and the most widely available. It is not the right answer to every problem, and specifying it reflexively is a common and expensive error — particularly in thermal management, where the need for electrical insulation rules it out entirely and h-BN is sitting there, commercially available, doing exactly the job.
The useful discipline is to state the requirement in terms of properties rather than materials, then check the family. Sometimes the answer is graphene. Often it is a mixture, and increasingly the interesting engineering lies in combining them.
This article is part of our Fundamentals series. For the closest comparison within carbon materials, see Graphene vs. Carbon Nanotubes: When to Use Which and Why. For graphene itself as the reference point, see What Is Graphene?. For MoSâ‚ in its most established commercial role, see Graphene in Lubricants.
