High Efficiency Production of Urea from Electrochemical Coreduction of Carbon Dioxide and Nitrite at Carbon Supported Iron(III) Tetrasulfophthalocyanine Under Ambient Conditions

Abstract

Electrochemical coreduction of carbon dioxide with nitrite can potentially be used to remove two serious pollutants from the environment while producing urea as an essential fertilizer and valuable fuel. However, efficiencies are currently much too low due to the high overpotentials required and/or low faradaic efficiency (FE) for urea formation. Although metal phthalocyanine catalysts can provide reasonably high FE (≤42%), high negative potentials (≤−0.75 V vs RHE) are required. Here it is shown that a water soluble, sulfonated iron(III) phthalocyanine can produce a higher FE for urea (54%) at +0.053 V vs RHE, with 25% coproduction of ammonia. Urea production was measured by the diacetyl monoxime (DAM) method, and verified by liquid chromatography–mass spectrometry. Electrodes prepared with a carbon black support and Nafion binder exhibited good stability in the 0.1 M NaHCO _3 electrolyte.