Functionalized Fe/Ni@g-C3N4 nanostructures for enhanced trichloroethylene dechlorination and successive oxygen reduction reaction activity

Mesoporous graphitic carbon nitride (g-C3N4) with open channels and high electron transport properties is in the limelight to serve as a catalyst support for environmental and energy applications. Herein, we have developed novel and environmentally friendly Fe/Ni@g-C3N4 nanocomposites for dual application in hydrodechlorination of trichloroethylene (TCE) and the consecutive oxygen reduction reaction (ORR). A homogeneous distribution of 2-3 nm Ni nanoparticles aligned onto the Fe-0 nanoparticles is observed to form bimetallic Fe/Ni nanocomposites. The decoration of Fe/Ni onto a few layers of lamellar g-C3N4 provides large surface area and accelerated electron transfer properties, resulting in the enhanced hydrodechlorination efficiency and rate of TCE. An 8-fold increase in the rate constant for TCE dechlorination by Fe/Ni@g-C3N4 is observed when the external voltage of -0.4 V is applied. Moreover, the generated iron oxides on the surface of Fe/Ni@g-C3N4 after the dechlorination exhibit superior electrocatalytic ORR activity with an electron transfer number of 3.9. In addition, the current density and onset potential of Fe/Ni@g-C3N4 are 3.6 mA cm(-2) and 0.84 V, respectively, which are close to those of standard Pt/C electrode materials. Results obtained in this work clearly demonstrate the excellence of Ni/Fe@g-C3N4 nanocomposites in consecutive applications to dechlorination and the ORR, which can open an avenue to design multifunctional metal@carbon nanocomposites as excellent electrochemical activity materials for water-energy nexus applications.