Niobium oxide/MXene heterostructure for simultaneous production of ammonia and energy via rechargeable Zn-N2 battery system

A high-stable Nb 2 O 5 /Nb 2 CT X heterostructure as electrocatalytic N 2 reduction reaction (ENRR) catalyst is fabricated. It enables a Zn-N 2 battery system with a high-power density of 1.25 mW cm −2 and a continuous net NH 3 production capacity. Aqueous Zn-N 2 batteries with unique configuration are of potential for simultaneous N 2 electroreduction and electricity generation, in which the electrocatalysts are critical for improving the NH 3 yield and the energy efficiency. Herein, a heterostructure Nb 2 O 5 /Nb 2 CT X with abundant exposed Nb active sites and tuned electron density has been synthesized by in situ formation and anchoring of Nb 2 O 5 nanoparticles on the surface of Nb 2 CT X MXene, which shows an enhanced N 2 adsorption/activation capacity. The heterostructure Nb 2 O 5 /Nb 2 CT X was used as the cathode of Zn-N 2 battery that can deliver a peak power density of 1.25 mW cm −2 in 1.0 M KOH and can continuously produce NH 3 with a yield of 3.62 μg h −1 mg cat −1 . The NH 3 formed in the battery system can be easily collected as a net product without circulating the electrolyte. Moreover, the Nb 2 O 5 /Nb 2 CT X has a long durability, evidenced by 70 h of operation at −0.4 V vs. reversible hydrogen electrode, which is the highest among the MXene-based electrocatalysts reported thus far. This work may provide a new methodology based on Zn-N 2 battery for sustainable and large-scale NH 3 production with minimal energy consumption.