Sulfur vacancy-rich ultrathin NiCo2Sx nanosheet arrays as a high-performance electrocatalytic reduction catalyst for nitrate to dinitrogen

Nitrate (NO3- ) electrocatalytic reduction is one of the most promising technologies for solving NO3- pollution in natural water. Nonprecious electrocatalysts with satisfactory cost and stable catalytic performance is essential to NO3- electrocatalytic reduction. Herein, a sulfur vacancy-rich ultrathin NiCo2Sx nanosheet arrays supported on a nickel foam electrode (denoted as U-NiCo2Sx/NF) is synthesized via simply a one-step constant current deposition strategy. The obtained U-NiCo2Sx/NF displays unique ultrathin sulfide nanosheet arrays, providing abundant infiltration space for NO3- transport, rich catalytic active site and enhanced structure stability. As such, the U-NiCo2Sx/NF exhibits outstanding NO3- electrocatalytic reduction performance with a high NO3- removal rate of 90.60 +/- 0.16 % at the conduction of 50 mg L- 1 initial NO3 - concentration (in terms of NO3 - -N), 120 min reaction time and 1.0 mA cm-2 working current density. Meanwhile, the N2 is the main final NO3- reduction product with a high N2 selectivity of 98.48 +/- 0.29 %. In addition, the U-NiCo2Sx/NF presents excellent chloride ion tolerance (<= 5000 mg L- 1) and electrochemical stability (20 electrolysis times). The cyclic voltammetry, i-t chronoamperometric and Tafel test further demonstrate the preeminent NO3- electrocatalytic reduction activity of U-NiCo2Sx/NF. This work may enlighten a simple paradigm to design stable and effective nonprecious electrocatalyst for NO3- electrocatalytic reduction.