Anderson-Type Polyoxometalate/Mxene Heterostructures for Efficient Electrochemical Nitrate Reduction to Ammonia

Abstract

The electrocatalytic conversion of nitrate into ammonia (NO3RR) represents a sustainable strategy for tackling nitrate pollution and simultaneously generating valuable ammonia. However, this process is often hindered by low Faradaic efficiency (FE) and insufficient ammonia yield rate. Herein, we report a novel class of 2D hybrid materials, NMo6-Tris@MXC (N = Fe, Co, Ni), synthesized through a "functionalize-then-condense" strategy that combines tris(hydroxymethyl)methane-modified Anderson-type polyoxometalates (NMo6-Tris) with carboxylated Ti3C2Tx MXene (MXC) via covalent amide linkages. This approach not only overcomes the intrinsic limitations of individual components but also substantially strengthens the antioxidative stability of the composite. Among the synthesized materials, CoMo6-Tris@MXC demonstrates enhanced NO3RR performance, attaining an NH3 yield of 4.993 mg h–1 mgcat.–1 and a FE of 98.7% at –1.0 V (vs. RHE), surpassing both pristine NMo6 and MXene. The composite maintains >95% of its initial activity over 12 h of continuous operation, showcasing remarkable stability. Research on the mechanism demonstrates that the covalent integration of NMo6 clusters suppresses the formation of undesirable intermediates, thereby promoting selective NH3 generation. This work not only provides a generalizable platform for designing POM-MXene hybrids but also advances the development of efficient electrocatalysts for sustainable nitrate remediation and ammonia synthesis.

Keywords: Polyoxometalate, Anderson-type polyoxometalate, MXene, Functionalization, Nitrate reduction reaction