1.1. Why electrochemical reduction of CO2 and associated challenges The electrochemical reduction of CO2 (CO2RR), driven by electrical energy from renewable sources, holds significant promise in mitigating the escalating levels of atmospheric CO2 and the resulting impact on Earth's climate. Moreover, such process presents an alternative avenue to traditional fossil resources as a sustainable carbon source9. To achieve efficient electrochemical CO2 reduction, substantial advancements in catalyst properties 10-12, electrode design (such as gas diffusion electrodes)13-15, and electrolyte composition16-18 have been reported. However, several challenges still need to be addressed before the technology becomes commercially viable19-20 , particularly in the context of aqueous electrolytes. These challenges encompass the low solubility of CO2 in water 21-23 , the acidification of the electrolyte due to CO2 dissolution (resulting in bicarbonate/carbonate formation and salt precipitation) 24-26, the concurrent occurrence of the competing hydrogen evolution reaction27-28, and the instability of metal and metal oxide catalysts in acidic aqueous environments29-30. 1.2. CO2 reduction in non-aqueous solvents The electrochemical inertness of organic solvents, such as acetonitrile, presents potential solutions to alleviate some of the issues mentioned earlier with aqueous media21, 23, 31. Notably, CO2 solubility in acetonitrile is approximately eight times higher than in water 32, a critical parameter that promotes enhanced CO2 utilization within the context of reactor design. The absence of water ensures a high selectivity towards CO2 reduction products. This is further reinforced by the consideration of the broad electrochemical window (electrochemical stability) of organic media, as well as the fact that CO2 becomes the sole redox-active species on the electrode-catalyst surface. For instance, acetonitrile and propylene carbonate have been reported to exhibit electrochemical windows of 6.1 V and 6.6 V, respectively 33.
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