Interfacial Engineering Promoting Electrosynthesis of Ammonia over Mo/Phosphotungstic Acid with High Performance

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Abstract
Electrochemical nitrogen reduction reaction (eNRR) is recognized as a promising approach for ammonia synthesis, which is, however, impeded by the inert nitrogen and the unavoidable competing hydrogen evolution reaction (HER). Here, a Mo‐PTA@CNT electrocatalyst in which Mo species are anchored on the fourfold hollow sites of phosphotungstic acid (PTA) and closely embedded in multi‐walled carbon nanotubes (CNT) for immobilization is designed and synthesized. Interestingly, the catalyst presents a high ammonia yield rate of 51 ± 1 µg h−1 mgcat.−1 and an excellent Faradaic efficiency of 83 ± 1% at −0.1 V versus RHE under ambient conditions. The concentrations of NH4+ are also quantitatively calculated by 1H NMR spectra and ion chromatography. Isotopic labeling identifies that the N atom of the formed NH3 originates from N2. The controlled experiments confirm a strong interaction between Mo‐PTA and N2 with an adsorption energy of 50.46 kJ mol−1 and activation energy of 21.36 kJ mol−1. More importantly, due to CNT's gas storage and hydrophobicity properties, there is a fourfold increase in N2 content. The concentration of H2O is reduced by more than half at the interface of the electrode. Thus, the activity of eNRR can be significantly improved with ultrahigh electron selectivity.
Funding Information
  • National Natural Science Foundation of China (22078063, 21825801, 21922813)

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