Interfacial Polarization Triggered by Covalent‐Bonded MXene and Black Phosphorus for Enhanced Electrochemical Nitrate to Ammonia Conversion

Abstract MXenes have recently emerged as a new class of electrocatalysts for diverse energy conversion reactions, but they are generally considered to be catalytically inert. Herein, a strategy of interfacial polarization is put forward to improve the catalytic activity of MXenes, with the construction of an interfacial structure consisting of black phosphorus (BP) nanoflakes and Nb 2 C MXene nanosheets for electrochemical nitrate reduction to ammonia as a proof of concept. The experimental and computational results reveal that a strong interfacial polarization is built between BP nanoflakes and Nb 2 C nanosheets in the prepared BP/Nb 2 C composite. The polarization of Nb centers by adjacent BP sites gives rise to the formation of positively centered Nb atoms and BP‐polarized Nb atoms, which synergistically catalyze the cleavage of N–O bonds in HNO 2 * to form NO*. In addition, the stabilization of monatomic *N by the BP/Nb 2 C composite is also enhanced compared with BP nanoflakes and Nb 2 C nanosheets. As a result, both the ammonia yield rate and Faraday efficiency of the BP/Nb 2 C composite are much higher than that of BP nanoflakes and Nb 2 C nanosheets. Overall, this work shows the great potential for constructing a strong interfacial polarization to improve the catalytic performance of MXenes‐based electrocatalysts.