{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/289717"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/289717","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Photoelectrochemical tandem cells with enzymes wired to hierarchically-structured electrodes for solar fuel synthesis","abstract":"In photosynthesis, solar energy drives the conversion of CO2 and H2O into chemical energy carriers and building blocks, releasing O2 as a by-product. Artificial photosynthesis attempts to mimic this process to produce a renewable and storable fuel, such as H2. Semi-artificial photosynthesis combines the strengths of natural photosynthesis with synthetic chemistry and materials science to develop model systems that overcome Nature’s limitations, such as low-yielding metabolic pathways and non-complementary light absorption by photosystem (PS) I and II. PSII, the first photosynthetic enzyme, is capable of photocatalytic water oxidation, a bottleneck reaction in artificial photosynthesis. The study of PSII in protein film photoelectrochemical (PF-PEC) platforms sheds light into its biological function and provides a blueprint for artificial water-splitting systems. However, the integration of biomolecules into electrodes is often limited by inefficient wiring at the biotic−abiotic interface. In this thesis, a range of tuneable hierarchically-structured electrodes was developed, constituting a versatile platform to accommodate a variety of biotic guests for PF-PEC cells. A new benchmark PSII−electrode system was assembled, that combined the efficient wiring afforded by redox-active polymers with the high loading provided by hierarchically-structured inverse opal indium tin oxide (IO-ITO) electrodes. A fully-integrated host−guest system showed a substantially improved wiring of PSII to the IO-ITO electrode with an Os complex-based and a phenothiazine-based polymer. Subsequently, a bias-free tandem semi-artificial cell was assembled, that wired PSII to hydrogenase for overall solar-driven water splitting. This PEC cell integrated the red and blue light-absorber PSII with a green light-absorbing diketopyrrolopyrrole dye-sensitised TiO2 photoanode enabling complementary panchromatic solar light absorption. Effective electronic communication at the enzyme−material interface was engineered using an Os complex-modified polymer on a hierarchically-structured IO-TiO2. Finally, a semi-artificial tandem device was designed, which performed solar-driven CO2 reduction to formate with formate dehydrogenase by coupling to the PSII−dye photoanode. The system achieved a metabolically-inaccessible pathway of light-driven CO2 fixation to formate and demonstrated a precious metal-free model for solar-driven selective CO2 to formate conversion using water as an electron donor. These semi-artificial platforms demonstrate the translatability and versatility of coupling selective and efficient electrochemical reactions to create challenging models and proof-of- principle devices for solar fuel synthesis. They provide a design protocol for bias-free semi-artificial Z-schemes and an extended toolbox of biotic and abiotic components to reengineer photosynthetic pathways. The assembly strategies presented here may form the basis of all-integrated electrode designs for a wide range of biological and synthetic catalysts.","abstract_html":"In photosynthesis, solar energy drives the conversion of CO2 and H2O into chemical energy carriers and building blocks, releasing O2 as a by-product. Artificial photosynthesis attempts to mimic this process to produce a renewable and storable fuel, such as H2. Semi-artificial photosynthesis combines the strengths of natural photosynthesis with synthetic chemistry and materials science to develop model systems that overcome Nature’s limitations, such as low-yielding metabolic pathways and non-complementary light absorption by photosystem (PS) I and II. PSII, the first photosynthetic enzyme, is capable of photocatalytic water oxidation, a bottleneck reaction in artificial photosynthesis. The study of PSII in protein film photoelectrochemical (PF-PEC) platforms sheds light into its biological function and provides a blueprint for artificial water-splitting systems. However, the integration of biomolecules into electrodes is often limited by inefficient wiring at the biotic−abiotic interface. In this thesis, a range of tuneable hierarchically-structured electrodes was developed, constituting a versatile platform to accommodate a variety of biotic guests for PF-PEC cells. A new benchmark PSII−electrode system was assembled, that combined the efficient wiring afforded by redox-active polymers with the high loading provided by hierarchically-structured inverse opal indium tin oxide (IO-ITO) electrodes. A fully-integrated host−guest system showed a substantially improved wiring of PSII to the IO-ITO electrode with an Os complex-based and a phenothiazine-based polymer. Subsequently, a bias-free tandem semi-artificial cell was assembled, that wired PSII to hydrogenase for overall solar-driven water splitting. This PEC cell integrated the red and blue light-absorber PSII with a green light-absorbing diketopyrrolopyrrole dye-sensitised TiO2 photoanode enabling complementary panchromatic solar light absorption. Effective electronic communication at the enzyme−material interface was engineered using an Os complex-modified polymer on a hierarchically-structured IO-TiO2. Finally, a semi-artificial tandem device was designed, which performed solar-driven CO2 reduction to formate with formate dehydrogenase by coupling to the PSII−dye photoanode. The system achieved a metabolically-inaccessible pathway of light-driven CO2 fixation to formate and demonstrated a precious metal-free model for solar-driven selective CO2 to formate conversion using water as an electron donor. These semi-artificial platforms demonstrate the translatability and versatility of coupling selective and efficient electrochemical reactions to create challenging models and proof-of- principle devices for solar fuel synthesis. They provide a design protocol for bias-free semi-artificial Z-schemes and an extended toolbox of biotic and abiotic components to reengineer photosynthetic pathways. The assembly strategies presented here may form the basis of all-integrated electrode designs for a wide range of biological and synthetic catalysts.","abstract_has_math":false,"creators":["Sokol, Katarzyna"],"institution":"University of Cambridge","degree_name":"PhD","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Reisner, Erwin"],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-03-23","date_published":"2019-03-23","updated_at":"2026-07-22T22:24:30Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/d8b08c6c-7701-47ff-b825-7c69177fe0df/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.36705","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Reisner, Erwin"]},{"key":"dc:creator","label":"Author","values":["Sokol, Katarzyna"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2019-03-23"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/289717"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["PhD"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/d8b08c6c-7701-47ff-b825-7c69177fe0df/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.36705"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/903dd51e-4685-4162-abfb-3161e8429403/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In photosynthesis, solar energy drives the conversion of CO2 and H2O into chemical energy carriers and building blocks, releasing O2 as a by-product. 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A new benchmark PSII−electrode system was assembled, that combined the efficient wiring afforded by redox-active polymers with the high loading provided by hierarchically-structured inverse opal indium tin oxide (IO-ITO) electrodes. A fully-integrated host−guest system showed a substantially improved wiring of PSII to the IO-ITO electrode with an Os complex-based and a phenothiazine-based polymer. Subsequently, a bias-free tandem semi-artificial cell was assembled, that wired PSII to hydrogenase for overall solar-driven water splitting. This PEC cell integrated the red and blue light-absorber PSII with a green light-absorbing diketopyrrolopyrrole dye-sensitised TiO2 photoanode enabling complementary panchromatic solar light absorption. Effective electronic communication at the enzyme−material interface was engineered using an Os complex-modified polymer on a hierarchically-structured IO-TiO2. 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