Elevating Nitrate Reduction through the Mastery of Hierarchical Hydrogen-Bond Networks

To effectively resolve environmental and industrial dilemmas, electrochemical reduction of nitrate (NO₃^–) to ammonia (NH₃) offers a brilliant strategy for tackling pollution and creating economic value, but the scarcity and reduced reactivity of available interfacial water and reactive adsorbates represent ongoing obstacles. Here, we reform the water–ion networks via electrolyte concentration manipulation and electrode construction on atomically flat Au single-crystal surfaces. With the combination of in situ Raman spectroscopy and multifidelity theoretical simulations, we pinpoint H₂O with dual hydrogen-bond donors as an observable indicator for nitrate electroreduction (NO₃RR). A hierarchical configuration characterized by structured Li⁺·NO₃^– planes coupled with enriched hydrogen-bond networks is verified to streamline the reactive intermediates activation and proton transport, thus synergistically boosting NO₃RR. We highlight the cooperative modulation of the interfacial water–ion interactions and the hydrogen-bond networks in optimizing NO₃RR. Our findings unveil microscale viewpoint of synergy between the local ion–water interactions and connectivity of the hydrogen-bonding network.