Boron phosphide as an efficient metal-free catalyst for nitrate electroreduction to ammonia.

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