Electrolyte and gas flow rate balance in flow cell for lithium-mediated ammonia electrosynthesis

Abstract

Electrochemical lithium-mediated nitrogen reduction (Li-NRR) has emerged as a leading approach for ammonia electrosynthesis under mild conditions, particularly in continuous flow-cell configurations. Despite the rapid progress of this strategy, as well as the remarkable efforts in electrolyte composition engineering and solid electrolyte interphase layer understanding, the impact of cell archicecture-level parameters remains unclear and is often entangled with the intrinsic process reactivity and selectivity. Here, we systematically investigate the influence of electrolyte and nitrogen gas flow rates on Li-NRR performance in a flow cell, attempting to decouple the effect of device-level parameters from reaction chemistry in determining activity, selectivity, and stability of the system. By balancing liquid and gas flows, we demonstrate stable device operation even at high electrolyte flow rates (18 mL min⁻¹), allowing for a complete exchange of the electrolyte in the liquid chamber twice per minute. This electrolyte flow rate results in a simultaneous improvement of Faradaic efficiency, productivity, and ammonia recovery in the gas phase. Overall, our results highlight the critical influence of cell architecture-related parameters on Li-NRR and emphasize the need to disentangle device engineering from electrolyte tailoring to enable a rational mechanism understanding, towards the translation of Li-NRR to a scalable process.