Carbon Dioxide Electrocatalytic Reduction Using Porphyrin/Graphene Systems

Yair Bochlin, Chemical Engineering, Ben Gurion University, Beer Sheva, Israel
Eli Korin, Chemical Engineering, Ben Gurion University, Beer Sheva, Israel
Armand Bettelheim, Chemical Engineering, Ben Gurion University, Beer Sheva, Israel

The CO₂ levels in air have been increasing over the past few decades. The conversion of CO₂ back to fuels is a critical goal that would restore balance to the rising CO₂ levels. CO₂ is a very stable, linear molecule, and returning it to a useful state in the form of fuels is a challenging problem. CO₂ reduction is possible through chemical catalysis, electrochemistry, photo-chemistry and biological processes. Chemical catalytic processes generally operate at high temperatures and pressures which lead to high energy cost.

The electrocatalytic capabilities toward CO₂ reduction of some cobalt porphyrins have been reported. The present work deals with the spectroscopic and electrochemical examination of the interactions occurring between such porphyrins and graphene derivatives, and their effect on CO₂ reduction. Such self-assembled systems formed between 5,10,15,20-Tetrakis(1-methyl-4-pyridinio) porphyrin (CoTMPyP) and carboxyl-rich graphene were deposited on electrode surfaces (such as glassy carbon) by means of adsorption or electrodeposition. TEM images show a homogeneously distributed CoTMPyP in the graphene sheets.

The electrodeposited system showed increased activity for CO₂ reduction compared to water reduction (1.2 mA/cm² and 0.25 mA/cm², respectively, at -1.2V vs. Ag/AgCl), as examined in an aqueous 0.1 M Na₂CO₃ solution at pH 11.5.