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Title: CO2 capture and photoconversion using multifunctional materials
Author: Crake, Angus
ISNI:       0000 0004 7658 6968
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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The sustainable production of energy is an exciting area for researchers requiring the development of improved technologies in both carbon dioxide (CO2) capture and CO2 utilization. This thesis presents the development and applications of bifunctional materials for CO2 capture by adsorption and utilization by photocatalytic conversion. Composite materials of solid sorbents and photocatalysts were designed primarily to increase CO2 abundance at the active sites and promote charge separation to aid photocatalytic activity. All materials were characterised using various structural, chemical and optoelectronic techniques. The materials were tested for CO2 capture and photoreduction using a gas-solid photoreactor. Composites of TiO2 and carbon nitride nanosheets (CNNS) were synthesised with control of the exposed TiO2 facets. When evaluated for CO2 adsorption and photocatalytic reduction the exposed TiO2 facets had significant influence in photocatalytic performance, the composite with more {001} facets exposed showed >10 fold higher activity than TiO2. TiO2 composites with metal organic frameworks (MOFs) were also designed; MOFs are an attractive class of materials for CO2 adsorption and their applications as photocatalysts are more recent. TiO2 and MOF (NH2-UiO-66) composites of various composition were evaluated for photocatalytic reduction of CO2 for the first time. The nanocomposites exhibited nanoparticle morphologies, maintained the CO2 adsorption capacity from the MOF component, and photocatalytically, the optimum composite was 1.5 times more active than TiO2 in conversion of CO2 to CO. Further enhancements in the TiO2/MOF composites were made by improving the TiO2-MOF interfaces by forming the MOF onto TiO2 nanofibers to promote more charge transfer. This resulted in a further 2.5-fold increase in photocatalytic reduction of CO2 to CO. A crucial phenomenon behind the improved photocatalytic activity of the composites was revealed by investigations of the charge dynamics, this showed successful formation of heterojunctions had facilitated interfacial charge transfer.
Supervisor: Petit, Camille Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral