Tuning nitrate reduction reaction selectivity via selective adsorption in electrified membranes

Improving electrochemical reactions by manipulating the properties of catalyst active sites often involves tradeoffs in activity, selectivity, stability and material costs. Here we incorporate a nitrite-adsorbing ionophore as a cooperative nitrite-enriching component into an electrified membrane to achieve high nitrate conversion (94.6%) and ammonia selectivity (91.9%) with a treatment time of only a few seconds (6 s). The ionophore enriched nitrite within the local electrocatalyst environment, facilitating conversion of unreacted nitrite to ammonia to inhibit overall nitrite formation (1.1%) without directly modifying the catalytic active sites. Integrating the ionophore as a selective adsorption component into a copper/carbon nanotube-based electrified membrane led to long-term selective ammonia production from low-concentration nitrate in real surface water and wastewater effluent without using precious metals. The concept of employing cooperative adsorption components to manipulate the local electrocatalyst environment and control reaction selectivity without precious metals or complex synthesis, especially when coupled with the stability and efficiency of scalable electrified membranes, could be extended to advance diverse electrocatalytic applications beyond nitrate. This study integrates a nitrite-adsorbing ionophore into a copper/carbon nanotube electrified membrane, enabling ultrafast and highly selective ammonia production from low-concentration nitrate in real water sources. This cooperative adsorption approach tunes the local catalyst environment to achieve high activity, selectivity and stability without using precious metals or complex synthesis methods.