Catalytic graphitization | MATES Laboratory

General context

Catalytic graphitization is a process that transforms disordered carbon materials, known as hard carbons, into graphitic structures through the action of metal catalysts at significantly lower temperatures than conventional graphitization methods. Hard carbons, which include materials like coal-tar pitch, petroleum coke, and various biomass-derived carbons, naturally resist structural ordering even when heated to extreme temperatures above 2500°C. However, when certain transition metals such as iron, nickel, cobalt, or their compounds are introduced, they facilitate the conversion by dissolving carbon atoms at elevated temperatures (typically 1000-1500°C) and precipitating them in a more ordered, layered graphitic arrangement. This catalytic mechanism involves the formation of metastable metal carbides or the diffusion of carbon through molten metal particles, which act as templates for graphene layer formation.

The importance of catalytic graphitization for sustainable synthetic graphite production cannot be overstated, particularly given the rapidly growing demand for high-quality graphite in lithium-ion batteries for electric vehicles and energy storage systems. Traditional synthetic graphite production through the Acheson process requires temperatures exceeding 2800°C and consumes enormous amounts of electrical energy—approximately 10-15 kWh per kilogram of graphite produced. By reducing the processing temperature by more than 1000°C, catalytic graphitization can potentially cut energy consumption by 50-70%, dramatically lowering the carbon footprint of synthetic graphite manufacturing. This energy efficiency improvement is crucial as the global graphite market is projected to grow exponentially, with battery-grade graphite demand expected to increase several-fold by 2030.

Furthermore, catalytic graphitization opens pathways for converting low-value carbon waste streams and renewable biomass into high-value graphitic materials, contributing to circular economy principles. Agricultural residues, industrial carbon byproducts, and even plastic waste can potentially be transformed into battery-grade graphite through this approach, reducing dependence on mined natural graphite while addressing waste management challenges. This is particularly significant because natural graphite mining has substantial environmental and social impacts, including habitat destruction, water pollution, and labor concerns in certain regions. By enabling the production of synthetic graphite from diverse, domestically available carbon sources at lower energy costs, catalytic graphitization represents a key technology for building more resilient and sustainable supply chains for the clean energy transition.

Turning Waste into High-Tech Carbon

Carbon has been at the heart of human technological development since ancient times, but today, graphite has become a “critical material” due to its indispensable role in green energy and battery technology. However, traditional methods for producing synthetic graphite are incredibly energy-intensive, requiring temperatures exceeding 3000 °C.

This is where catalytic graphitization changes the game. By heating carbon-rich precursors in the presence of an abundant, non-toxic catalyst like iron, we can achieve this transformation at much lower temperatures—often around 800 °C to 900 °C. This process is not just a scientific shortcut; it is a gateway to sustainable, high-performance materials.

How Does It Work?

The process typically involves mixing an organic precursor (like sugar, polymers, or biomass) with an iron source. As the mixture heats up, the iron drives a transformation where disordered, “amorphous” carbon becomes ordered, partially layered graphite. Graphitization proceeds by several mechanisms:

Dissolution-Precipitation: Disordered carbon dissolves into a tiny iron particle and then “pops out” as perfectly structured graphite layers.
Carbide Formation: The iron reacts with carbon to form a “metal carbide” (like Fe$_3$C), which then decomposes to leave behind graphitic structures.

Our research group, in collaboration with Prof. Schnepp’s group at the University of Birmingham, has focused on bridging the gap between raw biological resources and high-end technology. We specialize in converting natural biomass—such as wood and other plant-derived materials—into advanced carbons for electrochemical energy storage and wastewater treatment.

We have demonstrated that by using iron catalysts, we can maintain the intricate, interconnected pore structures found in wood while transforming the material into conductive graphite. This “nature-built” architecture provides a significant advantage for devices like supercapacitors, where the ability for ions to move quickly through pores is critical. We have successfully synthesized unique nanostructures, such as onion-like graphitic shells and curved graphitic layers, from wood precursors at temperatures significantly lower than traditional industrial methods.

Furthermore, to understand exactly how these materials form, we utilize advanced synchrotron-based tools. By studying these reactions in situ we have been able to identify the mechanisms behind catalytic graphitization. We also discovered that as the material cools, secondary transitions occur that trigger additional carbon precipitation, a nuance that would be impossible to see without the specialized X-ray tools we use.

Depending on the starting material and the catalyst ratio, this process can create a variety of nanostructures:

Carbon Nanotubes: Hollow, super-strong cylinders that are excellent conductors.
Graphitic Shells: Layered “cages” that can encapsulate and protect metal nanoparticles.
Bamboo-like Nanotubes: Segmented tubes that offer unique properties for filtering and energy.

Potential Applications: A Greener Future

The materials produced through these methods are much more than just “lab samples”; they are essential for the next generation of technology:

Better Batteries: Graphitic carbons are the preferred material for Lithium-ion battery anodes because they are stable and can be cycled many times.
Clean Energy: These carbons can replace expensive noble metals like platinum as catalysts in fuel cells.
Environmental Remediation: Because these structures can be made highly porous, they act as powerful filters for removing pollutants and heavy metals from water.

While humans have unknowingly used catalytic graphitization for millennia—from ancient pottery to Damascus steel—modern science is finally giving us the tools to master it. By using sustainable precursors like waste biomass and optimizing the process through in situ monitoring, we can produce the high-performance carbon the world needs without the heavy environmental toll of traditional manufacturing.

In Situ TEM and Synchrotron SAXS/WAXS Study on the Impact of Different Iron Salts on Iron-Catalysed Graphitization of Cellulose

Emily C. Hayward, Masaki Takeguchi, Harry J. Lloyd, Joshua M. Stratford, Andrew J. Smith, Tim Snow, Joaquin Ramírez-Rico, and Zoe Schnepp

Journal of Materials Chemistry A, 2025

DOI
Iron-Catalyzed Graphitization for the Synthesis of Nanostructured Graphitic Carbons

R. D. Hunter, J. Ramírez-Rico, and Z. Schnepp

Journal of Materials Chemistry A, 2022

DOI
Correlation of Structure and Performance of Hard Carbons as Anodes for Sodium Ion Batteries

Aurora Gomez-Martin, Julian Martinez-Fernandez, Mirco Ruttert, Martin Winter, Tobias Placke, and Joaquin Ramirez-Rico

Chemistry of Materials, Sep 2019

Abs DOI

Hard carbons are the material of choice as negative electrode in sodium ion batteries. Despite being extensively studied, there is still debate regarding the mechanisms responsible for storage in low- and high-potential regions. This work presents a comprehensive approach to elucidate the involved storage mechanisms when Na ions insert into such disordered structures. Synchrotron X-ray total scattering experiments were performed to access quantitative information on atomic ordering in these materials at the nanoscale. Results prove that hard carbons undergo an atomic rearrangement as the graphene layers cross-link at intermediate temperatures (1200–1600 ^∘C), resulting in an increase of the average interplanar distance up to 1400 ^∘C, followed by a progressive decrease. This increase correlates with the positive trend in the reversible capacity of biomass-derived carbons when processed up to 1200–1600 ^∘C due to an increased capacity at low potential (≤0.1 V vs Na/Na+). A decrease in achievable sloping capacity with increasing heat-treatment temperature arises from larger crystalline domains and a lower concentration of defects. The observed correlation between structural parameters and electrochemical properties clearly supports that the main storage of Na ions into a hard-carbon structure is based on an adsorption–intercalation mechanism.
Iron-Catalyzed Graphitic Carbon Materials from Biomass Resources as Anodes for Lithium-Ion Batteries

Aurora Gomez-Martin, Julian Martinez-Fernandez, Mirco Ruttert, Andreas Heckmann, Martin Winter, Tobias Placke, and Joaquin Ramirez-Rico

ChemSusChem, Sep 2018

Abs DOI

Graphitized carbon materials from biomass resources were successfully synthesized with an iron catalyst, and their electrochemical performance as anode materials for lithium-ion batteries (LIBs) was investigated. Peak pyrolysis temperatures between 850 and 2000 ^∘C were covered to study the effect of crystallinity and microstructural parameters on the anodic behavior, with a focus on the first-cycle Coulombic efficiency, reversible specific capacity, and rate performance. In terms of capacity, results at the highest temperatures are comparable to those of commercially used synthetic graphite derived from a petroleum coke precursor at higher temperatures, and up to twice as much as that of uncatalyzed biomass-derived carbons. The opportunity to graphitize low-cost biomass resources at moderate temperatures through this one-step environmentally friendly process, and the positive effects on the specific capacity, make it interesting to develop more sustainable graphite-based anodes for LIBs.
Structural Evolution in Iron-Catalyzed Graphitization of Hard Carbons

Aurora Gomez-Martin, Zoe Schnepp, and Joaquin Ramirez-Rico

Chemistry of Materials, May 2021

Abs DOI

Despite the recent interest in catalytic graphitization to obtain graphite-like materials from hard-carbon sources, many aspects of its mechanism are still poorly unknown. We performed a series of in situ experiments to study phase transformations during graphitization of a hard-carbon precursor using an iron catalyst at temperatures up to 1100 ^∘C and ex situ total scattering experiments up to 2000 ^∘C to study the structural evolution of the resulting graphitized carbon. Our results show that upon heating and cooling, iron undergoes a series of reductions to form hematite, magnetite, and wüstite before forming a carbide that later decomposes into metallic iron and additional graphite and that the graphitization fraction increases with increasing peak temperature. Structural development with temperature results in decreasing sheet curvature and increased stacking, along with a decrease in turbostratic disorder up to 1600 ^∘C. Higher graphitization temperatures result in larger graphitic domains without further ordering of the graphene sheets. Our results have implications for the synthesis of novel biomass-derived carbon materials with enhanced crystallinity.
Elucidating the Mechanism of Iron-Catalyzed Graphitization: The First Observation of Homogeneous Solid-State Catalysis

Robert D. Hunter, Masaki Takeguchi, Ayako Hashimoto, Kannan M. Ridings, Shaun C. Hendy, Dmitri Zakharov, Nils Warnken, Jack Isaacs, Sol Fernandez-Muñoz, Joaquín Ramirez-Rico, and Zoe Schnepp

Advanced Materials, May 2024

Abs DOI

Carbon is a critical material for existing and emerging energy applications and there is considerable global effort in generating sustainable carbons. A particularly promising area is iron-catalyzed graphitization, which is the conversion of organic matter to graphitic carbon nanostructures by an iron catalyst. In this paper, it is reported that iron-catalyzed graphitization occurs via a new type of mechanism that is called homogeneous solid-state catalysis. Dark field in situ transmission electron microscopy is used to demonstrate that crystalline iron nanoparticles “burrow” through amorphous carbon to generate multiwalled graphitic nanotubes. The process is remarkably fast, particularly given the solid phase of the catalyst, and in situ synchrotron X-ray diffraction is used to demonstrate that graphitization is complete within a few minutes.

General context

Turning Waste into High-Tech Carbon

How Does It Work?

Potential Applications: A Greener Future

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