(Invited) Curvature-Enhanced Hydrophobicity: A Counter-Intuitive Strategy for Efficient Electroreduction of Nitrate into Ammonia

The electrochemical upcycling of nitrate (NO 3 − ) to ammonia (NH 3 ) holds promise for synergizing both wastewater treatment and NH 3 synthesis. Efficient stripping of gaseous byproducts (NH 3 , H 2 , and N 2 ) from electrocatalysts is crucial for continuous and stable electrochemical reactions. This study evaluated a layered electrocatalyst structure using copper (Cu) dendrite to enable a high curvature and hydrophobicity and achieve a stratified liquid contact at the gas-liquid interface of the electrocatalyst layer. As such, gaseous product desorption or displacement from electrocatalysts was enhanced due to the separation of a wetted reaction zone and a non-wetted zone for gas-transfer. Consequently, this electrocatalyst structure yielded a 1.9-fold boost in per active site activity compared to that with a low curvature and high hydrophilic counterpart. Moreover, a high NH 3 Faradaic efficiency of 90.9 ± 2.3% was achieved with nearly 100% NO 3 − conversion. This high-curvature hydrophobic Cu dendrite was further integrated with a gas-extraction membrane, which demonstrated outstanding NH 3 yield from the real reverse osmosis retentate brine.