Now, Ib Chorkendorff and co-workers have identified diethylene glycol dimethyl ether (DG) as a candidate solvent with a high boiling point (162 °C) and excellent electrochemical stability that facilitates the formation of a compact catalytic SEI on the gas diffusion electrode (GDE). The designed continuous-flow reactor, featuring a 25 cm2 electrode, achieved energy efficiency values of 17%, ammonia Faradaic efficiency (FE) of 64%, and in total produced more than 4.6 g of ammonia after 300 h of continuous operation at ambient pressure and room temperature. Notably, more than 95% (4.5 g) of the produced ammonia was in the gas phase.
The researchers conducted screening of ether-based solvents, encompassing two categories of ring-ether-based solvents, namely THF and 1,3-dioxolane (DOL), as well as two types of chain-ether-based solvent, dimethoxyethane (DME) and DG. Their investigation revealed that DG exhibited the most promising results. Notably, they found that controlling the resting potential, rather than resting time, is critical for enhancing performance in the new solvent system, a strategy they defined as controlled cycling. By implementing controlled cycling with DME and DG, FE values of 81 ± 1% and 76 ± 1% were achieved, respectively, surpassing the FE obtained with THF (63 ± 1%). Moreover, the gas-phase distribution of ammonia exceeded 60% when using DG with controlled cycling.
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