Efficient reduction of Cr(VI) and elimination of total Cr with S-bridged Ni3S2/MoS2 nanowire electrode

Abstract

Electrochemical reduction of Cr(VI) is eco-friendly and cost-effective for eliminating the environmental risk of Cr-contaminated water. Herein, a novel Ni3S2/MoS2 nanowire electrode with a unique stem-leaf structure was synthesized for this purpose. Self-supported ultra-long Ni3S2 nanowires bearing MoS2 nanoflakes were in-situ grown from Ni foam with a hydrothermal method, in which Ni3S2 and MoS2 grow accompanied with each other by sharing some S atoms. Consequently, highly conductive out-stretched MoS2 nanoflakes wrap the Ni3S2 nanowires, providing aligned pathways for directional electron transfer and huge networks for the efficient reduction of Cr(VI) and high uptake of generated Cr(OH)3. The highest Cr(VI) removal rate attained at − 1.2 V approaches 0.005 mg/cm2 min, and elimination efficiency of total Cr is high up to 90.81 %. Although the adsorbed Cr(OH)3 on Ni3S2/MoS2 decreases the activity after repeated runs, the electrode can be restored by a simple pickling process with dilute acid, which has promising application prospects in the electrochemical reduction of Cr-contained wastewater.