Enhanced electrochemical ammonia synthesis enabled by an intermediate-temperature dual-ion conducting electrolyte

Electrochemical ammonia synthesis in solid oxide cells (SOCs) is a promising process, but its practical application is limited by the low ammonia production rate and insufficient efficiency. While electrolyte is known to affect performance, its precise role in modulating the catalytic reaction remains unclear. Here, we demonstrate that a proton/oxygen dual-ion conducting electrolyte-composed of BaZr_0.7Ce_0.2Y_0.1O_3-δ (BZCY) and Sm_0.2Ce_0.8O_2-δ (SDC)-can profoundly enhance the catalytic activity of the ammonia synthesis at the SOC cathode. The composite electrolyte exhibits an ionic transport number of 92% at 550 °C, with contributions of 52% from proton conduction and 40% from oxygen-ion conduction. The unique electrolyte properties create a proton-rich surface region and favorable oxygen-mediated during steam electrolysis, which accelerates the hydrogenation of nitrogen species. As a result, the SOC integrated with this dual-ion electrolyte achieves an order-of-magnitude increase in ammonia formation rate and a sixfold improvement in Faradaic efficiency over pure BZCY-based SOCs. This study demonstrates that rational electrolyte design is a powerful strategy for engineering the catalytic microenvironment, thereby enabling highly efficient ammonia synthesis.