The electrocatalytic capabilities toward CO2 reduction of some cobalt porphyrins have been reported in the literature, although at considerable overpotentials and low current densities. The present work aims to assemble an electrocatalytic system composed of cobalt porphyrins and graphene derivatives. Spectroscopic, microscopic and electrochemical methods are used to analyze the interactions occurring between such porphyrins and graphene derivatives, and their effect on CO2 reduction. Such self-assembled systems are formed between 5,10,15,20-Tetrakis(1-methyl-4-pyridinio) porphyrin (CoTMPyP) and graphene oxide (GO). This combination was electrodeposited on electrode surfaces, from aqueous solutions, using concessive cyclic voltammetry scans. Cross-section TEM-EELS images found dense distribution of CoTMPyP between the graphene sheets throughout the coating (figure 1). This arrangement of dense cobalt porphyrins between large conducting graphene sheets leads to enhanced electrocatalytic activity and formation of liquid-phase methanol as determined from GC-MS analysis.
The electrodeposited CoTMPyP-GO system showed increased electrochemical activity toward CO2 reduction vs. water reduction (0.7 and 0.3 mA/cm2, respectively, at -1.2V vs. Ag/AgCl), as examined in aqueous 0.1 M Na2CO3 solution at pH 11.5.