Boron phosphide (BP) is first explored as an efficient metal-free catalyst towards the NO 3 RR, delivering the highest NH 3 -faradaic efficiency of 96.3% with a corresponding NH 3 yield rate of 3.1 mg h -1 cm -2 , outperforming most reported metal-based NO 3 RR catalysts. Theoretical calculations unravel that active B centers not only enable the efficient NO 3 - activation and hydrogenation with a low energy barrier, but also preferentially absorb NO 3 - over H adatoms to prohibit the competing hydrogen evolution, enhancing both NO 3 RR activity and selectivity.