The article discusses the role of phenol as a proton shuttle in lithium-mediated ammonia electrosynthesis (Li-NRR). Phenol is found to exhibit the highest Faradaic efficiency (72 ± 3%) for ammonia production, surpassing the commonly used ethanol. The study evaluates various proton shuttles in a continuous-flow reactor with hydrogen oxidation at the anode, systematically screening and validating their effectiveness. Key design principles for effective proton shuttles are established, including the need for functional groups that can donate or accept protons, proper pKa values, and good electrochemical and chemical stability. The deprotonated form of phenol is shown to act as the primary species responsible for proton transfer during the Li-NRR process. The findings contribute to the understanding of the mechanistic aspects and design principles for efficient proton shuttles in practical Li-NRR applications, paving the way for sustainable and environmentally friendly ammonia production methods.The article discusses the role of phenol as a proton shuttle in lithium-mediated ammonia electrosynthesis (Li-NRR). Phenol is found to exhibit the highest Faradaic efficiency (72 ± 3%) for ammonia production, surpassing the commonly used ethanol. The study evaluates various proton shuttles in a continuous-flow reactor with hydrogen oxidation at the anode, systematically screening and validating their effectiveness. Key design principles for effective proton shuttles are established, including the need for functional groups that can donate or accept protons, proper pKa values, and good electrochemical and chemical stability. The deprotonated form of phenol is shown to act as the primary species responsible for proton transfer during the Li-NRR process. The findings contribute to the understanding of the mechanistic aspects and design principles for efficient proton shuttles in practical Li-NRR applications, paving the way for sustainable and environmentally friendly ammonia production methods.