Sustainable photocatalysis using carbon-based materials through interfacial and solvent engineering

With global warming and the energy crisis posing critical global challenges, the development of efficient, low-cost, and scalable photocatalytic systems for solar-fuel production has gained significant attention as a pathway toward a sustainable carbon economy. Among the wide range of semiconducting materials investigated, carbon-based nanomaterials have been considered as promising candidates due to their non-toxicity, scalability, cost-effectiveness, and distinctive optical and physicochemical properties. Nevertheless, despite considerable research efforts, photocatalytic fuel conversion using carbon-based nanomaterials remains insufficiently explored with limited commercial value. This limitation arises from intrinsic drawbacks such as rapid charge-carrier recombination, restricted charge transport, limited density of catalytically active sites, and poor electrical conductivity. To overcome these limitations, this thesis explores interfacial and solvent engineering strategies aimed at suppressing charge recombination and improving charge transfer efficiency in solar-fuel conversion systems, where carbon-based nanomaterials serve as primary light harvesters in combination with transition metals, molecular catalysts, and biocatalysts. A homogeneous photocatalytic CO2 reduction system was established using graphitic nitrogen-doped carbon dots with a cobalt molecular catalyst, where rational electrostatic interactions enhanced interfacial electron transfer and modified the catalytic pathway for efficient CO2 reduction. Furthermore, interfacial interaction between carbon dots and methyl viologen enabled efficient and robust charge extraction from carbon dot, which subsequently generated ultra-long-lived radical species, achieving an oxidative quenching pathway. In addition, covalent modification of carbon dots with methyl viologen was employed to develop an efficient biohybrid system with Shewanella oneidensis MR-1 for ethanol and H2 co-production from glycerol upcycling, enhancing extracellular charge transfer between bacteria and abiotic nanomaterials. Finally, an air-tolerant solar reforming system for biomass and plastics was demonstrated by tailoring the reaction medium, which suppressed side reactions and improved photocatalytic performance. Overall, this thesis introduces interfacial (electrostatic interaction and covalent modification) and solvent engineering approaches to unlock the potential of carbon-based nanomaterials in solar-fuel conversion. The combination of earth-abundant materials, tuneable surface chemistry, and broad co-catalyst compatibility provides a versatile platform for developing next-generation photocatalytic systems to address global energy and environmental challenges.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Kim, Dongseok

Advisor dc:contributor.advisor

• Reisner, erwin

• Sustainable energy
• Photocatalysis
• Carbon-based materials
• Interfacial engineering
• Solvent engineering

Licence

• https://www.repository.cam.ac.uk/bitstreams/a57e1e9a-069b-4846-a624-73e4a1aeff9c/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.123372

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/392768