Enhanced performance of molecular electrocatalysts for CO2 reduction in a flow cell following K+ addition

Electrocatalytic CO2 reduction is a key aspect of artificial photosynthesis systems designed to produce fuels. Some molecular complexes can act as electrocatalysts for CO2 reduction and the performance of these compounds can be controlled by varying their ligands and substituents. However, these compounds also suffer from poor durability and energy conversion efficiency. The present work demonstrates the drastically improved CO2 reduction activity exhibited by molecular catalysts in a membrane electrode assembly cell. These catalysts were composed of a cobalt-tetrapyridino-porphyrazine complex supported on carbon black together with a potassium salt, and were both stable and efficient. These systems were found to promote electrocatalytic CO2 reduction with a current density of 100 mA/cm2 and generated CO over a span of at least one week with a selectivity of approximately 95%. The optimal catalyst gave a turnover number of 3,800,000 and an energy conversion efficiency more than 62% even at 200 mA/cm2.