Codeposition of cobalt phthalocyanine (CoPc) with axially-coordinating poly(4-vinylpyridine) (P4VP) from DMF inhibits aggregate formation in the deposition solution and in the resulting CoPc-P4VP composite layer. Surface-immobilized CoPc is an active and selective catalyst for the electrochemical reduction of CO<sub>2</sub> to CO. However, like most phthalocyanines CoPc is susceptible to formation of stacked aggregates, limiting the number of possible catalytic active sites in a deposited layer. Dissolution with axially-coordinating solvents is an established method for hindering phthalocyanine aggregation in solution. In this research, we use transmission UV-Vis, UV-Vis ATR, and electron microscopy to quantify aggregation through variation in the CoPc Q-band absorbance. CoPc-P4VP/DMF solutions have less aggregation at high CoPc concentration compared to solutions of equivalent concentration without a polymer or with a non-coordinating polymer. Similarly, when dropcast onto an electrode surface, CoPc-P4VP composite films have lower levels of aggregation than films of CoPc without a polymer or with non-coordinating polymers. These results suggest that codeposition with an axially-coordinating polymer is an effective strategy for increasing the availability of catalytic active sites for surface-immobilized CoPc electrocatalysts.

Mitigating cobalt phthalocyanine aggregation through codeposition with an axially-coordinating polymer

ACS Fall 2021

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