Reduction of CO2 on Metals

Nevertheless, all proposed mechanisms share the common intermediate species C02 ads which is the product of a highly energetic one-electron process (reactirai 10). This explains the high overpotentials required for successful reduction of CO2 on metal electrodes with high and medium HER overpotentials. 

On the other hand, the electrochemical reduction of CO2 on metal electrodes with low HER overpotential is completely different. It has been shown that CO2 reacts with Hads> leading to tightly bound COads (reactions 15-16) [14—16]. Since the formation of Hads on the Pt surface requires litde overpotential, the overall CO2 reduction reaction is achieved very efficiently, though only stoichiometrically. The formed COads binds very tightly to the Pt and poisons the surface of the metal, a problem well known in catalysis on Pt surfaces. 

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