Asymmetric Push–Pull Type Co(II) Porphyrin for Enhanced Electrocatalytic CO2 Reduction Activity

Abstract

Molecular electrocatalysts for electrochemical carbon dioxide (CO2) reduction has received more attention both by scientists and engineers, owing to their well-defined structure and tunable electronic property. Metal complexes via coordination with many π-conjugated ligands exhibit the unique electrocatalytic CO2 reduction performance. The symmetric electronic structure of this metal complex may play an important role in the CO2 reduction. In this work, two novel dimethoxy substituted asymmetric and cross-symmetric Co(II) porphyrin (PorCo) have been prepared as the model electrocatalyst for CO2 reduction. Owing to the electron donor effect of methoxy group, the intramolecular charge transfer of these push–pull type molecules facilitates the electron mobility. As electrocatalysts at −0.7 V vs. reversible hydrogen electrode (RHE), asymmetric methoxy-substituted Co(II) porphyrin shows the higher CO2-to-CO Faradaic efficiency (FECO) of ~95 % and turnover frequency (TOF) of 2880 h−1 than those of control materials, due to its push–pull type electronic structure. The density functional theory (DFT) calculation further confirms that methoxy group could ready to decrease to energy level for formation *COOH, leading to high CO2 reduction performance. This work opens a novel path to the design of molecular catalysts for boosting electrocatalytic CO2 reduction.

A universal route to graft highly dispersed cobalt phthalocyanine on porous carbon for efficient CO2 electroreduction

“…The Tafel slopes (Fig. 3g) for all CoPc/PC- x catalysts were very similar to previous reported values on metal porphyrins and phthalocyanines, 32–34 presenting values much closer to 110 mV dec −1 . The results indicated that the CO 2 RR process over CoPc/PC- x was limited by initial electron–proton transfer to generate a *COOH intermediate.…”

Artificial Photosynthesis: Current Advancements and Future Prospects

“…To this end, catalysts based on metal-containing phthalocyanines or porphyrins have been developed, which have demonstrated considerable efficacy for this process [ 140 , 141 , 142 ]. In this regard, Qiu et al [ 143 ] synthesized two novel electrocatalysts for CO 2 reduction by employing dimethoxy-substituted Co(II) porphyrin. The authors suggested that the methoxy group’s electron donor effect facilitated the intramolecular charge transfer, thereby promoting electron mobility.…”

“…The authors suggested that the methoxy group’s electron donor effect facilitated the intramolecular charge transfer, thereby promoting electron mobility. Furthermore, theoretical calculations using density functional theory (DFT) confirmed that the methoxy group could substantially affect the energy levels of the process, thereby enhancing CO 2 reduction efficiency [ 143 ]. In another study, Shi et al [ 144 ] synthesized a hybrid cobalt(II) phthalocyanine-COOH/carbon nanotube (CNT) catalyst by anchoring CoPc-COOH onto the surface of carbon nanotubes.…”