Tuning the d-band centers of bimetallic FeNi catalysts derived from layered double hydroxides for selective electrocatalytic reduction of nitrates

Electrochemical cathode with high activity and durability is crucial for the treatment of nitrate-polluted water bodies. Herein, we developed an approach to grow the bimetallic FeNi catalyst derived from layered double hydroxides (FeNi LDM) on carbon cloth as the cathode for efficient electrocatalytic nitrate-N (NO3−-N) reduction. Through tuning the d-band centers of the bimetallic catalysts, the FeNi LDM cathode achieved an optimal nitrate removal rate of 98% with a reaction rate up to 1.4 h−1 and a nitrogen (N2) selectivity of 100% in 3 h at an initial NO3−-N concentration of 30 ppm and 250 ppm NaCl. Electrochemical measurements demonstrated that the electrical conductivity of FeNi LDM was improved due to the synergistic effects of the bimetallic composition. Density function theory (DFT) calculations showed that the alloying of Fe and Ni could adjust the d-band centers of FeNi LDM, facilitating the balance of adsorption and desorption of intermediates and resulting in a rapid conversion of nitrate. And FeNi LDM showed the superior operational durability over five consecutive cycle tests. Additionally, the FeNi LDM catalyst was capable of treating the high-concentration effluent (500 ppm NO3−-N) with a NO3−-N removal efficiency of 95% within 5 h at a current utilization efficiency (η) of 81%. Most importantly, the catalytic system maintained the superior performance towards treating with real industrial wastewater (effluent of a coking wastewater treatment plant), indicating the great potentials for real applications.