Covalently immobilised cobalt-based molecular catalyst for carbon dioxide electroreduction
The electrocatalytic reduction of carbon dioxide (CO2) to value-added products is an attractive ‘green’ way to mitigate global warming and resolve energy crisis issues. Nowadays, molecular catalysts are considered to be promising for industrial CO production due to their high atom efficiency and versatile ligand environment. Heterogenisation method has a significant effect on their performance, yet it is one of the least studied fields. In this thesis, for the first time, cobalt(II) phthalocyanine was covalently linked to carbon-based electrode with C-C bond. Compared to noncovalently immobilized CoPc, covalently grafted catalyst produced 2 times more CO with 2-fold higher turnover frequency TOF(CO) and 33 % higher Faradaic efficiency towards CO (FE(CO)). After a 24 h electrolysis, covalently grafted CoPc retained 50 % of the active sites as opposed to 35 % for noncovalently immobilised CoPc. Based on the experimental data, the mechanism involving the Co0 as a catalytically active site is proposed. The improved catalytic performance may be attributed to a more facile electron transfer through the C-C bond. This work is a great addition to heterogenised molecular catalysts active in CO2-to-CO electroreduction and it lays the foundation of a new subclass of covalently attached Pc based catalysts.