Electronic Modulation of Bi-Decorated Ti3C2Tx MXene Toward Highly Efficient Electrocatalytic Nitrate Reduction to Ammonia

Abstract

Electrochemical nitrate reduction (NO₃RR) provides a sustainable route for ammonia (NH₃) synthesis while also enabling the treatment of nitrogen-containing wastewater. Herein, Bi nanoparticles were anchored on Ti₃C₂T_x MXene through an in situ reduction strategy to form Bi–NP/MXene. Compared with pristine MXene, Bi–NP/MXene exhibits markedly improved NO₃RR activity and NH₃ selectivity, achieving a Faradaic efficiency of 93.2% at −1.2 V versus reversible hydrogen electrode (RHE) and an NH₃ yield rate of 195.3 μmol h⁻¹ cm⁻² at −1.4 V versus RHE. The catalyst retains stable performance over six consecutive cycles and 1200 min of continuous electrolysis. Density functional theory calculations reveal that Bi incorporation regulates nitrate-derived intermediate adsorption, suppresses H* binding, and reduces the energy barrier of the potential-determining step from 1.36 to 0.74 eV. Moreover, a Zn–NO₃⁻ battery employing Bi–NP/MXene enables simultaneous NH₃ production and electricity generation.