Electrochemical Reduction of Carbon Dioxide to Fuels Using Graphene-Cobalt Porphyrin Catalytic Coatings

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 carbon dioxide levels in the air have been increasing over the past few decades and passed 400 ppm in 2016. CO₂ is the most significant greenhouse gas which has major effects on the environment such as global warming and ocean acidification. The capture and conversion of atmospheric CO₂ is a critical goal that would have a significant impact on earth’s atmosphere.

CO₂ reduction is possible through chemical catalysis, electrochemistry, photochemistry and biological processes. Chemical catalytic processes generally operate at high temperatures and pressures which lead to high energy cost. Electrochemical methods, however, operate at ambient conditions which offer a simple and effective route for CO₂ reduction.

The major difficulty associated with the electrochemical reduction of CO₂ is the formation of CO₂^.- anion radical, a reaction intermediate, which is more energetic compared to the stable linear CO₂ molecule. This reaction intermediate leads to significant overpotentials required for CO₂ reduction. In addition, water reduction is a competing reaction when operating in aqueous solution, which lowers the efficiency. Thus an efficient and selective electrocatalytic system is required.  

Metalloporphyrins are an important class of organometallic materials that are based on natural catalysts found in nature. The electrocatalytic capabilities toward CO₂ reduction of some cobalt based porphyrins have been reported in the literature. The present work deals with the spectroscopic, microscopic and electrochemical examination of the interactions occurring between such porphyrins and graphene derivatives, and their effect on CO₂ reduction. Such self-assembled systems which are formed between Co(II)5,10,15,20-Tetrakis(1-methyl-4-pyridinio)porphyrin (CoTMPyP) and graphene oxide (GO) were deposited on electrode surfaces by means of electrodeposition. The electrodeposited GO-CoTMPyP system showed increased activity for CO₂ reduction vs. water reduction (1.4 and 0.8mA/cm², respectively, at -1.2V vs. Ag/AgCl), as examined in aqueous 0.1M Na₂CO₃ solution at pH 11.5. Examination of other graphene derivatives for CO₂ reduction is in progress.