Cyanide-Coordinated Fe(III) Meso-Tetra(4-carboxyphenyl) Porphyrin as a Possible Electrocatalytic Material for Selective H2S Oxidation

Abstract

Electrodeposited Fe(III) meso-Tetra(4-carboxyphenyl) porphyrin with cyanide ligands coordinated to the central iron ion was investigated as a possible material capable of selectively oxidizing H2S in the presence of CO and NO in physiologically relevant solutions. Preliminary results suggest this to be an attractive material as it oxidized H2S at low potentials (0.15 V vs. Ag/AgCl) while exhibiting only mild activity toward both CO and NO. While this is a step in the right direction, the selectivity is currently inadequate for practical applications. Additionally, the electrocatalyst also exhibited a limited response at elevated sulfide concentrations, presumably due to the deposition of S0 on the electrode surface. However, a cathodic-post run treatment was able to regenerate the electrochemical activity of the porphyrin-modified electrode surface by stripping any S0 that deposited on the electrode surface during the H2S oxidation. The imperfect porphyrin coverage of the electrode surface and incomplete coordination of cyanide are suspected as the primary reasons for these shortcomings. Research is ongoing to remedy these limitations.