Construction of electron-deficient Co on the nanoarrays enhances absorption and direct electron transfer to accelerate electrochemical nitrate reduction

Abstract

Electrochemical nitrate reduction is a promising remediation strategy for nitrate-contaminated wastewater treatment, in which nitrate adsorption is a prerequisite step in the overall process. Herein, the iron-induced cobalt phosphide was grown in situ on porous nickel foam (Fe-CoP/NF) for the electrochemical nitrate reduction. Structural characterization verified doping of Fe and the uniform nanotube arrays of Fe_0.03CoP/NF. Remarkably, the Fe_0.03CoP/NF exhibited a high efficiency nitrate removal efficiency (99.3%) and excellent ammonia selectivity (100% selectivity and 0.485 mg·h^-1cm^-2 NH₃ yield rate). Both experimental and theoretical results reveal that Fe doping alters the local charge distribution of the Co active centers to form electron-deficient Co. The Co electron-deficient regions were constructed due to the difference in electronegativity between Co and Fe. Furthermore, the formation of electron-deficient centers facilitates the reduction of charge transfer resistance. In particular, Fe_0.03CoP/NF maintained an excellent conversion efficiency of nitrate to N₂ (99.8%) with 60 mM Cl⁻, and the selectivity of N₂ is maintained above 99.1% during long-term operation. This system possesses a low electrical consumption of 1.79 kWh·mol_N^-1. This study designed an enhanced electrocatalyst through enhanced nitrate absorption and direct electron transfer strategies, thus providing a promising and low-power consumption approach for addressing nitrate pollution.