Catalytic Conversion of Waste Plastics to Hydrogen and Carbon Nanomaterials

The catalytic conversion of waste plastics into hydrogen and carbon nanomaterials represents an integrated approach to both mitigate plastic pollution and generate value-added products. At its core, the process employs thermochemical routes—most commonly pyrolysis coupled with steam reforming—to break down long-chain polymers into smaller molecules. Metal catalysts, notably Ni, Fe or Ni-Fe alloys supported on oxides or zeolites, facilitate dehydrogenation and reforming reactions, enhancing hydrogen yield while promoting the formation of graphitic carbon. Control of reaction parameters such as temperature, steam-to-plastic ratio and catalyst composition allows co-production of hydrogen and carbon nanotubes, nanofibres or graphene-like sheets. Emerging strategies extend beyond purely thermal processes, exploring photocatalytic and electrocatalytic routes that exploit light or electrical energy to activate polymer fragments at lower temperatures. The resulting hydrogen can serve in fuel cells or chemical synthesis, while the carbon nanomaterials find applications in composite reinforcement, energy storage and electronics. By closing the loop on plastic wastes and harvesting high-value commodities, catalytic conversion supports a circular carbon economy. Ongoing challenges include catalyst deactivation by coke deposition, scale-up of reactor designs and cost-effective catalyst synthesis. Advances in catalyst architecture and reactor engineering promise to accelerate the transition from laboratory demonstrations to industrial deployment.

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Catalytic Conversion of Waste Plastics to Hydrogen and Carbon Nanomaterials publication trend

The graph below shows the total number of articles in catalytic conversion of waste plastics to hydrogen and carbon nanomaterials across all publications each year (not limited to Nature Index journals).

Technical terms

Pyrolysis: Thermal decomposition of organic materials in the absence of oxygen to yield gas, liquid and solid residues.

Steam reforming: Endothermic reaction of hydrocarbons with water vapour over a catalyst to produce hydrogen and carbon monoxide.

Carbon nanotubes: Cylindrical nanostructures composed of rolled graphene sheets, valued for high strength and electrical conductivity.

Bimetallic catalyst: A catalyst comprising two different metals, which often exhibit enhanced activity or selectivity due to synergistic interactions.

Fixed-bed reactor: A reactor configuration in which catalysts are held stationary in a packed bed through which reactant gases flow.

References

1. Upcycling of plastic wastes for hydrogen production: Advances and perspectives. Renewable and Sustainable Energy Reviews (2024).
2. Co-production of hydrogen and carbon nanotubes from real-world waste plastics: Influence of catalyst composition and operational parameters. Applied Catalysis B Environment and Energy (2018).
3. Structure-oriented conversions of plastics to carbon nanomaterials. Carbon Research (2022).