Heterostructured assembly of ternary SnS/Mo2S3/g-C3N4 nanocomposites for high-performance hybrid supercapacitors, photodegradation of organic dyes and Cr(<sc>vi</sc>) reduction

Abstract

Designing heterostructure-based nanocomposites has gained considerable interest in solving energy scarcity and environmental contamination issues. Herein, a heterojunction assembly of ternary SnS/Mo2S3/g-C3N4 nanocomposites with varying Sn and Mo weight ratios was synthesized through a single-step hydrothermal method. At an optimized ratio of tin to molybdenum (1 : 2), denoted as SM-3, promising electrochemical and photocatalytic performances were observed compared to bare SnS/g-C3N4 and Mo2S3/g-C3N4. It displayed a maximum specific capacity of 200 C g-1 at a current density of 1.0 A g-1 and the lowest equivalent series resistance among the prepared electrodes, as revealed by electrochemical measurements. For real-time applications, the fabricated device SM-3(+)||activated carbon(-) delivered an energy density of 37.24 Wh kg-1 at a power density of 756 W kg-1 with a capacity retention of 85% for continuous 5000 cycles of charge-discharge. The remarkable energy storage performance was evident by powering a 3 V blue light-emitting diode when three such devices were connected in series. Photocatalytic studies revealed a photoreduction of 95.2% of Cr(vi) (20 mg L-1) to non-toxic Cr(iii) and photodegradation of 91% of eosin yellow dye (20 mg L-1) with a minimal catalyst dosage (0.3 g L-1) within 120 min of irradiation through a first-order kinetic process. The negative conduction band potential (-1.21 eV) of SM-3, as estimated by Mott-Schottky analysis, confirmed the involvement of O2(center dot)- radicals and photogenerated electrons in the degradation process, which was further confirmed by radical trapping experiments. Charge carriers followed a double Z-scheme pathway that lowered the recombination rate.