Boron‐Doped Ti3C2Tx MXene for Effective and Durable High‐Current‐Density Ammonia Synthesis

Abstract

AbstractAmmonia (NH3) synthesis via the nitrate reduction reaction (NO3RR) offers a competitive strategy for nitrogen cycling and carbon neutrality; however, this is hindered by the poor NO3RR performance under high current density. Herein, it is shown that boron‐doped Ti3C2Tx MXene nanosheets can highly efficiently catalyze the conversion of NO3RR‐to‐NH3 at ambient conditions, showing a maximal NH3 Faradic efficiency of 91% with a peak yield rate of 26.2 mgh−1 mgcat.−1, and robust durability over ten consecutive cycles, all of them are comparable to the best‐reported results and exceed those of pristine Ti3C2Tx MXene. More importantly, when tested in a flow cell, the designed catalyst delivers a current density of ‒1000 mA cm−2 at a low potential of ‒1.18 V versus the reversible hydrogen electrode and maintains a high NH3 selectivity over a wide current density range. Besides, a Zn–nitrate battery with the catalyst as the cathode is assembled, which achieves a power density of 5.24 mW cm−2 and a yield rate of 1.15 mgh−1 mgcat.−1. Theoretical simulations further demonstrate that the boron dopants can optimize the adsorption and activation of NO3RR intermediates, and reduce the potential‐determining step barrier, thus leading to an enhanced NH3 selectivity.