Modulating Electronic Structure of Cobalt Ion Via MXene-Supported Mesoporous Carbon for Enhanced Nitrate Reduction and Ammonia Synthesis in Zn-NO3− Batteries

Abstract

The nitrate reduction reaction (NO3RR) is an eight-electron/nine-proton process that proceeds through multiple nitrogen-containing intermediates with distinct electronic and spin configurations. This intrinsic complexity poses a major challenge for the rational design of highly efficient electrocatalysts. Herein, we report an MXene-supported mesoporous carbon heterostructure containing dispersed Co species, denoted as MXene/MC-Co, in which support-Co interactions modify the local electronic environment of Co and its interactions with key adsorbed intermediates. As a result, the MXene/MC-Co catalyst delivers an ammonia yield rate of 5500 μg h−1 mgcat.−1 with a Faradaic efficiency of 80.12% for NO3RR. Furthermore, a Zn−NO3− battery assembled with MXene/MC-Co as the cathode achieves a high power density of 8 mW cm−2 and a Faradaic efficiency of 87.4% at a current density of 12 mA cm−2, enabling simultaneous ammonia synthesis and electrical energy output. This work demonstrates a support-engineering strategy for tuning the local electronic environment of metal species and highlights the role of metal−support interactions in promoting nitrate electroreduction.