( Invited ) New Approaches to Catalyzing CO 2 R with Cobalt Phthalocyanine Integrated with Carbon Nanotubes

Cobalt phthalocyanine (CoPc) is an established molecular catalyst for the electrochemical reduction of carbon dioxide (CO 2 R) to CO. Recent studies have shown that CoPc immobilized on carbon nanotubes can enable direct CO 2 R to methanol at highly reducing potentials, enabling remarkable demonstrations of selectivity in electrochemical CO 2 R. Here, we present a recent application of CoPc to the cascade production of methanol as well as fundamental work on the integration of the catalyst with carbon nanotubes. Most CO 2 R pathways feature CO as an intermediate, making product selectivity vs CO production challenging. However, it may be possible to design cascading reactions where CO 2 is first reduced to CO and then CO is subsequently consumed to selectively generate a desired product. Implementing cascading reactions in a PEC device would be challenging given the need to co-locate catalytic microenvironments on a mm scale. We recently demonstrated the use of a three-terminal tandem (3TT) photocathode with CoPc coupled to multi-walled carbon nanotubes (MWCNT). The 3TT photocathode generated two operating potentials, allowing the CoPc/MWCNT catalyst to drive both the generation of CO and the subsequent reduction of CO to methanol. The champion integrated photocathode produced methanol with 3.8± 0.4% Faradaic efficiency (FE), and methanol production continued over repeated experiments with the same photocathode. Methanol production ceased when the 3TT subcell driving CO reduction was deactivated, supporting the assignment of a cascade mechanism. Although there are now several examples of CoPc integrated with carbon nanotubes, which strains the CoPc and alters the catalytic pathway for methanol production, there has been little exploration of mechanisms of charge transfer from the carbon nanotubes to CoPc. Furthermore, this work has not taken advantage of advances in carbon nanotube design which may enable fine-tuning of integrated catalytic properties. We will discuss progress on the integration of CoPc with carbon nanotubes and their influence on fundamental reactivity of this catalyst.