Efficient carbon dioxide (CO2) conversion strategies are critically important to alleviate global warming and energy shortage issues. The electrochemical CO2 reduction reaction (CO2RR), powered by renewable energy resources, offers sustainable pathways for long-term energy storage. Metal phthalocyanines (MePcs) are an attractive class of electrocatalysts due to cost-effectiveness, accessibility, and superior thermal and chemical stabilities. More importantly, the well-defined M-N4 structure in MePcs is considered a well-established model to understand the CO2RR mechanism. However, the CO2RR activity and selectivity of MePcs are inferior to state-of-art catalysts which limit their future applications. Herein, we developed an axial ligand modification strategy on cobalt phthalocyanine (CoPc) molecules to raise the CO2RR efficiency and selectivity. In this work, organic molecules, which elevated Co dz2 orbital energy by changing the Co coordination geometry from square planar to square pyramidal, was anchored at the axial positions of CoPc. Simultaneously, a reduced Co oxidation state was noticed due to the change of electron density through the electron pulling effect implemented by the presence of axial ligands. The aforementioned synergistic effect effects enhanced the interactions between Co active sites and CO2. Axial ligand modified CoPc molecules (CoPc-py and CoPc-im) exhibited excellent catalytic activity and selectivity in converting CO2 into CO.

Axial ligand-induced d orbital reordering and electron pulling effect on metal phthalocyanine to enhance CO2 conversion performance

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.