Nature Water, Published online: 10 August 2026; doi:10.1038/s44221-026-00694-x Phase engineering of high-entropy nanoalloys can enhance electrocatalysis. A one-pot synthesized 2H RhCuNiInSb nanoalloy outperformed its face-centred cubic counterpart for nitrate reduction, enabling efficient NH3 production and wastewater denitrification through an optimized electronic structure.