About

Dr. Pulickel Ajayan is the leader of the Ajayan Research Group at Rice University, which focuses on advanced nanomaterials with applications in alternative energy, multifunctional nanocomposites, and electronics/sensor technologies. The group's ongoing projects emphasize the materials science and engineering of technologies that have the potential to impact society significantly in the future. Key research areas include energy generation and storage, chemical sensors, nanoelectronics, flexible displays, high-performance composites, membrane technologies, coatings, and biomedical technologies. Dr. Ajayan's group collaborates extensively both within Rice University and with external partners, engaging in multidisciplinary efforts to develop functional nanomaterials for a wide variety of applications. The Ajayan Research Group is dedicated to changing the world through discoveries and the development of new materials.

Research topics

• Materials science
• Nanotechnology
• Chemistry
• Optoelectronics
• Organic chemistry
• Engineering
• Physics
• Optics
• Metallurgy
• Crystallography
• Chemical engineering
• Composite material
• Computer Science
• Engineering physics
• Photochemistry
• Molecular physics
• Quantum mechanics
• Medicine
• Atomic physics
• Electrical engineering
• Embedded system
• Thermodynamics
• Waste management
• Computational chemistry

Selected publications

• Beyond DESs: Aqueous Redox‐Active Amino Chloride Salts for Efficient Hydrometallurgical Recycling of Lithium‐Ion Batteries

  Small · 2026-04-24

  articleSenior author

  ABSTRACT Recycling lithium‐ion batteries has gained momentum over the past few years owing to the escalating demand for critical materials, with Deep Eutectic Solvents (DES) being noted as alternative green lixiviants for hydrometallurgical pathways. While polarity, pH, and H‐bonding contribute to the high leaching efficiencies (LE) of these solvents, the exact role of the eutectic composition remains unclear. Moreover, high viscosities of DESs often lead to high temperature and time requirements, deterring their facile commercialization. Herein, we propose a new class of lixiviants, namely, aqueous amino chloride solutions, which mimic the necessary and sufficient properties of DESs while overcoming the constraints of high viscosity and low thermal conductivity. Among these, Hydroxylammonium chloride or hydroxylamine hydrochloride (HACl:H 2 O) solution shows remarkable ultrafast leaching performance, with ∼65% LE of all metals within 1 min at room temperature. Closer insights into the leaching pathway reveal that while pH balance and presence of a redox center play a crucial role in this rapid leaching, polarity and eutectic composition are not major contributors. A comparative study of different amino chloride solutions performed here leads to a better understanding of the leaching process and demonstrates that satisfying the necessary properties for leaching in different solvent systems can lead to the future design of smarter, more efficient, and sustainable lixiviant systems.

  PublisherDOI

• Flow-induced 2D nanomaterials intercalated aligned bacterial cellulose

  Nature Communications · 2025-07-01 · 17 citations

  articleOpen access

  Bacterial cellulose is a promising biodegradable alternative to synthetic polymers due to the robust mechanical properties of its nano-fibrillar building blocks. However, its full potential of mechanical properties remains unrealized, primarily due to the challenge of aligning nanofibrils at the macroscale. Additionally, the limited diffusion of other nano-fillers within the three-dimensional nanofibrillar network impedes the development of multifunctional bacterial cellulose-based nanosheets. Here, we report a simple, single-step, and scalable bottom-up strategy to biosynthesize robust bacterial cellulose sheets with aligned nanofibrils and bacterial cellulose-based multifunctional hybrid nanosheets using shear forces from fluid flow in a rotational culture device. The resulting bacterial cellulose sheets display high tensile strength (up to ~ 436 MPa), flexibility, foldability, optical transparency, and long-term mechanical stability. By incorporating boron nitride nanosheets into the liquid nutrient media, we fabricate bacterial cellulose-boron nitride hybrid nanosheets with even better mechanical properties (tensile strength up to ~ 553 MPa) and thermal properties (three times faster rate of heat dissipation compared to control samples). This biofabrication approach yielding aligned, strong, and multifunctional bacterial cellulose sheets would pave the way towards applications in structural materials, thermal management, packaging, textiles, green electronics, and energy storage. NCOMMS-24-62603C. The potential applications of bacterial cellulose (BC) have been limited by challenges in aligning nanofibrils at the macroscale and creating BC-based multifunctional nanosheets. Here, the authors report a strategy of using shear forces from fluid flow in a rotational culture device to biosynthesize strong BC sheets with aligned nanofibrils, and BC-based multifunctional hybrid nanosheets.

  PublisherOA PDFDOI

• Ray H. Baughman (1943–2025) – A tribute from the Carbon Journal

  Carbon · 2025-10-07

  articleOpen access
  PublisherOA PDFDOI

• Sustainable WO ₃ /rGO Nanocomposite Anode for Room and High‐Temperature Sodium‐Ion Storage

  Small · 2025-08-20 · 1 citations

  articleCorresponding

  Abstract The synthesis, structure, morphology, and electrochemical properties of tungsten trioxide (WO 3 ) and reduced graphene oxide (rGO) nanocomposites (WO 3 /rGO) are investigated for their potential as anode materials in sodium‐ion batteries (NIBs). Electrochemical analyses revealed that WO 3 /rGO outperformed bare WO 3 , demonstrating stable cycling, high‐rate capability, and enhanced performance. The composite delivered initial discharge/charge capacities of ≈285/350 mAh g −1 with an initial Coulombic efficiency of ≈81%, stabilizing at ≈285 mAh g −1 after 150 cycles. It exhibited a remarkable rate retention of ≈49% at 2000 mA g −1 and exceptional cycling stability over 600 cycles. High‐temperature testing improved ionic conductivity and stability, maintaining ≈99% Coulombic efficiency across all conditions. Further, the high‐temperature (70 °C) cycling stability of a cell is evaluated at 100 mA g 1 for 250 cycles, where, after initial stabilization, it maintained consistent performance with ≈180 mAh g 1 reversible capacity and ≈100% Coulombic efficiency. Density Functional Theory (DFT) calculations are carried out to investigate the electronic structure, sodium storage, and ion mobility, showing that rGO incorporation lowers the Na diffusion energy barriers, contributing to the higher Coulombic efficiency and reversibility. These results highlight the potential of WO 3 /rGO nanocomposites as efficient, durable anode materials for next‐generation NIBs under diverse operating conditions.

  PublisherDOI

• Polyanionic Materials-a New Class of Electrocatalysts for Alkaline Water/Seawater Electrolysis

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  In the field of electrocatalysis, a wide range of catalysts have been developed for water splitting applications. Noble metal-based catalysts, such as those containing Pt, Ru, or Ir, are regarded as benchmark materials for driving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, due to their high cost and scarcity, extensive research has focused on identifying cost-effective alternatives based on non-precious metals. Among these, transition metal (Ni, Fe, Co) polyanionic materials show great promise owing to their well-defined crystalline structures and versatile synthetic tunability. Polyanions (phosphate, sulfate, oxalate etc.) offer strong covalent bonding with oxygen, which stabilizes the structure of the material during harsh redox conditions in alkaline media. Moreover, the inductive effect from polyanions can modulate the electronic structure of the active metal centers, optimizing the adsorption energies of intermediates (e.g., *OH, *O, *OOH) in water splitting. Substituting different metal centers or varying the polyanionic group allows tunable redox activity and optimized electronic conductivity, making them good candidates for both OER and HER. Here, the transition metal cations act as primary active sites in electrochemical processes and exhibit significant catalytic activity. The fast transformations on electrochemically active surfaces result in accelerated kinetics, a decreased overpotential barrier, and increased stability. These catalysts are mostly investigated for alkaline water electrolysis. The presentation will focus on the design of transition metal-based oxalate and phosphate catalysts, highlighting their performance in both the OER and HER. It will also emphasize how tuning the composition can effectively modulate their catalytic activity.

  PublisherDOI

• From Glaphene to Glaphynes: A Hybridization of 2D Silica Glass and Graphynes

  ArXiv.org · 2025-09-17

  preprintOpen access

  Hybrid two-dimensional (2D) materials have attracted increasing interest as platforms for tailoring electronic properties through interfacial design. Very recently, a novel hybrid 2D material termed glaphene, which combines monolayers of 2D silica glass and graphene, was experimentally realized. Inspired by glaphenes, we proposed a new class of similar structures named glaphynes, which are formed by stacking SiO$_2$ monolayers onto $α$-, $β$-, and $γ$-graphynes. Graphynes are 2D carbon allotropes with the presence of acetylenic groups (triple bonds). The glaphynes' structural and electronic properties were investigated using the density functional tight-binding (DFTB) method, as implemented in the DFTB+ package. Our analysis confirms their energetic and structural stability. We have observed that in the case of glaphynes, the electronic proximity effect can indeed open the electronic band gap, but not for all cases, even with the formation of Si-O-C bonds between silica and graphynes.

  PublisherOA PDFDOI

• A Semiconductor Composite with High Solid‐State Lubrication and Low Thermal Conducting Properties

  Advanced Functional Materials · 2025-11-17 · 1 citations

  articleSenior authorCorresponding

  Abstract Ceramic composites exhibiting the combination of light‐weight, semiconducting behavior, low thermal conductivity, and solid‐state lubrication are crucial for advanced applications in electronics, thermal insulation, and wear‐resistant components, enabling efficient performance under demanding conditions. However, obtaining these functionalities simultaneously in a single material is nontrivial because these properties often require opposing structural and compositional features. Here, the synthesis of spark plasma sintered SiOC‐BN ceramic composite by combining amorphous silicon oxycarbide (SiOC) with crystalline hexagonal boron nitride (h‐BN) is reported. Comprehensive structural and microscopic characterizations confirm the existence of uniformly distributed h‐BN and cubic β ‐SiC phases throughout the bulk material. The composite exhibits a p ‐type semiconducting behavior with nearly isotropic electrical resistivity and low cross‐plane thermal conductivity at room temperature. Mechanical and tribological testing further reveal the excellent strength and solid‐state lubrication under high mechanical loads, with a low coefficient of friction. Comparative structure‐property correlations with individual SiOC and h‐BN ceramics highlights the synergistic effects of the combined phases, contributing to the composite's properties. These findings show the potential of SiOC‐BN ceramic composite as a promising material for future technologies.

  PublisherDOI

• Nitrogen-Terminated Diamond Films for Antiscaling Coatings

  ACS Nano · 2025-11-14 · 1 citations

  articleSenior authorCorresponding

  Mineral scaling, particularly gypsum deposition, remains a costly and persistent problem in industrial systems, lowering efficiency, raising energy demands, and accelerating equipment degradation. Conventional chemical and mechanical mitigation methods are temporary and often introduce secondary environmental or operational concerns, underscoring the need for intrinsically scale-resistant materials. Herein, we report a systematic investigation of polycrystalline diamond (PCD) films with varied surface terminations (oxygen, hydrogen, fluorine, or nitrogen) for their resistance to CaSO4 scaling. Nitrogen-terminated PCD (N-PCD) exhibits an order-of-magnitude reduction in Ca2+ accumulation compared with other terminations. Scanning electron microscopy (SEM) reveals that N-PCD supports only sparse, dendritic gypsum crystallites, in contrast to the dense, continuous scale layers observed on other surfaces. Consistently, adhesion force measurements confirm extremely low adhesion between the CaSO4 crystal and N-PCD. Molecular dynamics and density functional theory simulations show that a strongly bound, ordered water layer forms on N-PCD, creating an energetic barrier that repels CaSO4 ions and suppresses heterogeneous nucleation. Further enhancement is achieved by bulk nitrogen doping, which smooths the surface morphology and suppresses scale formation by up to 6-fold. Finally, applying nitrogen functionalization to commercial boron-doped diamond (BDD) electrodes yields seven times lower scale loading without compromising electrochemical performance. This combined experimental–theoretical study establishes nitrogen-functionalized diamond as a robust, durable platform for antiscaling coatings, with potential applications across water treatment, energy production, and other scaling-prone industries.

  PublisherDOI

• Attosecond inner-shell lasing at ångström wavelengths

  Nature · 2025-06-11 · 7 citations

  articleOpen access
  PublisherOA PDFDOI

• Challenges of Anodes in Sodium-Ion Batteries

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  Sodium-ion batteries (NIBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) due to sodium's abundance and low cost. However, developing high-performance anode materials remains a critical challenge due to sodium's larger ionic radius and sluggish kinetics Na⁺ than Li⁺. Traditional graphitic carbon, which has proven successful in lithium-ion systems, exhibits limited intercalation capacity for Na⁺ (~35 mAh g⁻¹) due to thermodynamically unfavorable Na-carbon intercalation into graphitic layers. As a result, graphitic carbon is mainly unsuitable for practical NIB anodes without significant structural modification. In contrast, hard carbon, a disordered, turbostratic form of carbon, has demonstrated superior Na⁺ storage capacity (>300 mAh g⁻¹), attributed to a combination of adsorption at defect sites, intercalation into nanopores, and sloping voltage profiles. Despite these advantages, hard carbon faces challenges, including poor initial Coulombic efficiency, limited rate capability, and cycling instability. [1] Understanding the complex Na⁺ storage mechanisms in hard carbon and optimizing its pore structure, surface chemistry, and conductivity is critical for advancing SIB anode performance. [2] This abstract highlights the fundamental and practical challenges in employing carbonaceous anodes for NIBs, emphasizing the need for advanced structural design, doping strategies, and hybrid composite approaches to unlock their full potential for next-generation energy storage systems. This study demonstrates the promise of graphitic carbon cones and discs as high-performance anodes for sodium-ion batteries (Figure 1a, b), leveraging their unique structures to overcome the limitations of conventional graphite and hard carbon and paving the way for viable beyond-lithium energy storage solutions. [3] References: [1] S. K. Saju, S. Chattopadhyay, J. Xu, S. Alhashim, A. Pramanik, P. M. Ajayan, Cell Rep Phys Sci. 2024, 5, 101851. [2] S. Chattopadhyay, A. Pramanik, T. Pieshkov, G. Chandrasekhar, S. Alhashim, R. Vajtai, P. M. Ajayan, Small 2025. DOI: 10.1002/smll.202500120. [3] A. Pramanik, S. Suriyakumar, T. Pieshkov, S. Chattopadhyay, S. K. Saju, V. Vijayan, B. Zechmann, D. Berti, M. M. Shaijumon, P. M. Ajayan, Adv. Funct. Mater. 2025, 2505848. Figure 1

  PublisherDOI

Recent grants

• Inter-American Materials Collaboration: Large Scale Synthesis of N-doped Carbon Nanotubes for the Fabrication of Novel Polymer Composites and Related Low Dimensional Materials

  NSF · $246k · 2003–2008

• EAGER/Collaborative Research: Coaxing Graphene to be Piezoelectric

  NSF · $24k · 2011–2012

• Materials World Network: Fabrication of Polymer Composites and Sensors using Doped Nanotubes

  NSF · $288k · 2008–2011

Frequent coauthors

• Róbert Vajtai

  Rice University

  622 shared

• Chandra Sekhar Tiwary

  238 shared

• Anand B. Puthirath

  Rice University

  200 shared

• Jun Lou

  186 shared

• A. Glen Birdwell

  DEVCOM Army Research Laboratory

  168 shared

• Jordan A. Hachtel

  Oak Ridge National Laboratory

  145 shared

• Abhijit Biswas

  Rice University

  143 shared

• Tony Ivanov

  DEVCOM Army Research Laboratory

  143 shared

Labs

• Ajayan Research GroupPI

  1-2 sentence research focus

Awards & honors

• Senior Humboldt Prize
• 2006 MRS Medal
• Scientific American 50 recognition in 2006
• RPI Senior Research Award (2003)
• Burton Award from the Microscopic Society of America (1997)