1 School of Civil Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China.
2 School of Civil Engineering and Architecture, Taizhou University, Taizhou 318000, China.
3 School of Environmental Science and Engineering, Hebei Key Laboratory of Pollution Prevention Biotechnology, Hebei University of Science and Technology, Shijiazhuang 050018, China.
4 Department of Building, Civil, and Environmental Engineering, Concordia University, 1455 de Maisonneuve Blvd. W. Montreal, Quebec, Canada.
5 School of Environmental Science and Engineering, Hebei Key Laboratory of Pollution Prevention Biotechnology, Hebei University of Science and Technology, Shijiazhuang 050018, China; School of Civil Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China. Electronic address: lianjing@hebust.edu.cn.
6 School of Civil Engineering and Architecture, Taizhou University, Taizhou 318000, China. Electronic address: jianbguo@163.com.

Inefficient electron transfer is one of the main challenges in practical denitrification applications. To address this issue, a novel ternary mediator functional material (Mxene@Fe-TA) was successfully synthesized, which exhibited pseudocapacitive properties to facilitate electron mediation and distribution. Batch experiments revealed that 50 mg/L MXene@Fe-TA achieved 2.04-fold nitrate degradation. This superior performance originated from three integrated mechanisms: (1) MXene@Fe-TA served as a pseudocapacitor, which stored electrons from substrate metabolism by electrochemical structure; (2) it fostered a microenvironment that selectively enriched electroactive bacteria (EAB), which boosted secretion of redox-active substances to accelerate extracellular electron transfer (EET); and (3) the battery function of MXene@Fe-TA facilitated the stored electrons flowed directionally to denitrification, thereby optimizing energy utilization and reducing metabolic demands. This study introduced an innovative strategy for denitrification and guided the design of multifunctional materials to improve the efficiency of biological wastewater treatment.