The work performed in this project has covered several aspects related to the main scope, which is the development of molecular catalyst/semiconductor assemblies for carbon dioxide reduction.
Visible light driven carbon dioxide reduction (publication 1): A new hybrid photocatalyst was developed by polymerizing cobalt phthalocyanine on carbon nitride. While phthalocyanines are traditionally used as colorants in green and blue pigments, metal phthalocyanines are known for their interesting redox properties. We used cobalt phthalocyanine polymer as a the 'molecular catalyst' component in the hybrids. Porous carbon nitride, a highly stable solid semiconductor composed of carbon and nitrogen, served as the light harvester in the hybrid system. Upon visible light illumination, an electron/hole pair is generated in carbon nitride. The excited electron gets transferred to the cobalt phthalocyanine anchored on the surface to form reduced metal centre that subsequently catalyses conversion of carbon dioxide to carbon monoxide. The holes on carbon nitride is quenched by a sacrificial electron donor to complete the redox cycle. One milligram of hybrid material generated approximately 0.5 micromol of CO after 24 h visible light irradiation.
Coupled electrolyzer (publication 2): The same polymeric cobalt phthalocyanine catalyst was for electricity driven carbon dioxide reduction in an electrolyzer device. The prototype device consists of a novel anode that oxidizes alcohol to aldehyde and a cobalt phthalocyanine cathode that reduces carbon dioxide and water to syngas (mixture of CO and hydrogen). Electricity provides the energy for the coupled electrolyzer and the electron generated from alcohol oxidation (anode) is utilized for syngas production at cathode. The energy efficiency of the cell, defined as the ratio of the chemical energy stored in the products and the energy input, is estimated to be approximately 17%.
Photoelectrode for carbon dioxide reduction (manuscript 4): p-doped silicon is widely used photovoltaic industry and is considered as one of the most promising materials for fabrication of photoelectrodes. We therefore employed a silicon wafer as photoelectrode which contained a mesoporous titanium dioxide protection layer. A newly designed cobalt phthalocyanine catalyst with four phosphonic acid anchoring groups was immobilized on the titania surface. The photocathode assembly displayed good activity towards syngas generation from CO2 saturated aqueous solution under visible light illumination.
Publications:
1) Souvik Roy, Erwin Reisner, Light driven CO2 reduction by mesoporous carbon nitride modified with polymeric cobalt phthalocyanine, Angew. Chem. Int. Ed., 2019, 58, 12180–12184
2) Mark A. Bajada†, Souvik Roy†, Julien Warnan†, Kaltum Abdiaziz, Andreas Wagner, Maxie M. Roessler, Erwin Reisner, A Precious-metal-free Hybrid Electrolyzer for Alcohol Oxidation Coupled to CO2-to-syngas Conversion, Angew. Chem. Int. Ed., 2020, doi: 10.1002/anie.202002680
3) Stefan Vanicek, Markus Jochriem, Christopher Hassenrück, Souvik Roy, Holger Kopacka, Klaus Wurst, Thomas Müller, Rainer F. Winter, Erwin Reisner, Benno Bildstein, Redox-Rich Metallocene Tetrazene Complexes: Synthesis, Structure, Electrochemistry and Catalysis, Organometallics, 2019, 38, 1360–1371
4) Souvik Roy, Melanie Miller, Julien Warnan, Jane Leung, Erwin Reisner, Electrocatalytic and Solar-Driven Reduction of Aqueous CO2 with Immobilized Molecular Cobalt-Phthalocyanine Catalyst, in preparation
5) Arjun Vijeta, Souvik Roy, Erwin Reisner, Nickel modified mesoporous carbon nitride for organic transformations, in preparation
Conference Talks:
1) Visible-light driven carbon dioxide reduction by metal-organic polymer integrated carbon nitride (ISF-3), Electrocatalytic hydrogen evolution from a cobaloxime-Based metal–organic framework thin film (ISF-3 Young); 3rd International Solar Fuels Conference (ISF-3/ICARP2019); Hiroshima, Japan; November 19-24, 2019
2) Visible-light driven CO2 reduction by carbon nitride modified with polymeric cobalt-phthalocyanine; 7th UK Solar Fuel Network Symposium (UK-SFN); St. John’s College, Cambridge, UK; March 28-29, 2019
Invited Seminars:
1) When molecule meets materials: Developing hybrid organic/inorganic catalysts for sustainable energy applications; King’s College London (KCL), Research Seminar; London, UK; August 1, 2019
