When CO2 is encapsulated in clathrate hydrate, where the concentration is nearly two orders of magnitude greater than in saturated aqueous solution, the rate of the CO2 reduction reaction (CO2RR) increases, and the corresponding Faradaic efficiency becomes up to three times higher than that of the competing hydrogen evolution reaction (HER) at applied potential of -0.5 to -0.7 VRHE. The energy efficiency of the CO2RR is correspondingly increased. When the magnitude of the applied voltage is increased further the advantage of the clathrate encapsulation is diminished. The enhanced CO2RR in clathrate is ascribed to non-equilibrium release of the CO2 due to the electric field near the electrode, analogous to what has been observed recently for tetrahydrofuran [Li et al. J. Phys. Chem. Letters 125, 13802 (2021)]. This raises the chemical potential of CO2 beyond that of saturated aqueous solution, thereby reversing the relative rate of the CO2RR and the HER. The results reported here demonstrate this release mechanism for the application of CO2 up-conversion.
1. Improved the resolution of the main figures. 2. Changed some typos in the reference, for example, in reference (3), there was an extra 'i.,', and 'Co 2' should be CO2.
Clathrate Hydrates Increase the Efficiency of Electrochemical CO2 Reduction