The construction of an electrocatalytic NO3 − reduction and polyacrylamide (HPAM) oxidation coupled reaction system represents a promising approach for simultaneously achieving ammonia synthesis and HPAM degradation. In this work, FeCo@N-CNTs with a well-defined heterojunction structure were successfully synthesized and employed as an efficient bifunctional electrocatalyst in the NO3 − reduction and HPAM oxidation coupled reaction. In the coupled reaction system, The FeCo@N-CNTs catalyst delivered a maximum ammonia yield rate and Faradaic efficiency of 6097.96 ± 15.83 μg h− 1 mgcat −1 and 92.03 ± 1.48%, respectively, while achieving an HPAM degradation rate of 89.99 ± 0.37% within 2 h. In-situ ATR-SEIRAS and in-situ DEMS analyses identified *NHOH as a key intermediate during the ammonia synthesis process and revealed that the heterojunction structure effectively regulates charge distribution and active-site exposure on the catalyst surface. This study offers a new strategy for designing coupled electrochemical systems toward efficient NO3⁻ reduction and organic pollutant oxidation, providing valuable insights for sustainable nitrogen-cycle conversion and wastewater treatment.

Construction of FeCo@N-CNTs heterojunction structures for efficient electrocatalytic cathodic nitrate reduction coupled with anodic HPAM oxidation reactions
    Abstract
    1 Introduction
    2 Experimental section
    3 Results and discussion
        3.1 The structure and morphology of FeCo@N-CNTs and its comparison samples
        3.2 Performance of FeCo@N-CNTs and comparison samples in the electrocatalytic oxidative degradation of HPAM
        3.3 Unraveling the origin of electrocatalytic activity and reaction mechanisms
    4 Conclusions
    References

• Lijie Qi(Shenyang Fire Research Institute of MEM, Shenyang 110034, China)
• Shujun Liu(Shenyang Fire Research Institute of MEM, Shenyang 110034, China) Corresponding author
• Yu Fu(Kazakh-British Technical University, Almaty 050000, Kazakhstan)