Exploration of the g-C₃N₄ Heterostructure with Ag–In Sulfide Quantum Dots for Enhanced Photocatalytic Activity

Abstract

Photocatalysis is an effective technology to convert solar energy into chemical energy, which has attracted great attention for the degradation of water pollutants and the hydrogen production by water splitting. The nonmetallic polymer g-C3N4 (GCN) can meet the thermodynamic conditions of photocatalytic water splitting, but its performances are not satisfying due to its narrow light absorption range and high recombination rate of photogenerated charge carriers. Among metal sulfide semiconductors, Ag–In sulfide quantum dots (AIS QDs), such as AgInS2, show excellent visible light absorption and promising photoactivity. In this work, AIS QDs-modified GCN is synthesized by an in situ growth method in mild conditions. The photocatalytic activity of the AIS-QDs/GCN nanocomposite is notably higher than that of the pure phase g-C3N4. Especially, the sample containing 10 wt % AIS QDs has the best activity in both tetracycline degradation and hydrogen generation, reaching 48.5% degradation efficiency in 1 h of visible light exposure (3.2 times that of GCN) and a hydrogen evolution rate of 62.3 μmol·g–1·h–1 (that of bare GCN being negligible). The optical and photoelectrochemical characterization highlights the interplay between the two components, suggesting that the enhanced photocatalytic activity of AIS-QDs/GCN is mainly due to the broadening of the light absorption range, the acceleration of charge transfer, and the reduction of the carrier pair recombination rate due to the formation of a type-II heterojunction inside the composite catalyst. This work is among the first attempts to modify g-C3N4 with polysulfide quantum dots to improve its catalytic performance, and the results provide an important step for advances in the application of these systems.

Activities of BiFeO3/carbon-dots catalysts in piezo-photocatalytic degradation of ciprofloxacin upon light/ultrasonic excitation

“…S5 , the spectral shapes and peaks of the emission band for the BiFeO 3 barely changes after the incorporation of CQDs, but the emission intensity decreases obviously. It means that the recombination of charge carrier pairs in CODs decorated BiFeO 3 is reduced [26] . Among all the prepared catalysts, the BiFeO 3 /C-0.12 catalyst has the lowest emission intensity, indicating the lowest recombination probability of photoinduced pairs in the photocatalyst.…”

“…For obtaining more active sites, the widely used methods are size and morphological control [18] , [20] , [21] , as well as integration with organic materials [22] , [23] , [24] . For suppressing recombination of photoinduced pairs, a widely used method is to form heterojunction structure with other materials [17] , [19] , [22] , [25] , [26] , [27] , [28] .…”

Regulating Deep and Shallow Defects of CuInS2 Quantum Dots To Enhance Photocatalytic Hydrogen Production

“…The use of fossil fuels also releases large amounts of greenhouse gases (CO 2 ), and the concentration of carbon dioxide in the atmosphere has increased from 280 ppm before preindustrial period to 413.2 ppm. , As an efficient and clean energy source, hydrogen energy has the advantages of being storable and renewable and has the highest energy density (142 MJ·kg –1 ) among all chemical fuels, which makes it a hot research topic for alleviating energy shortage and environmental pollution . Using photocatalytic decomposition of water to produce H 2 is one of the most ideal ways to fundamentally solve the energy and environmental problems and also the way to prevent the environmental pollution caused by fossil energy. − Semiconductor QDs are a widely studied new catalyst in the field of solar hydrogen production. − Recently, various semiconductor QDs have been widely studied as photoabsorbers in heterogeneous or homogeneous photocatalytic systems. − Unfortunately, early QDs maintained a low photocatalytic efficiency due to excessive electron–hole recombination, poor exciton separation efficiency, and limited active sites. Thereafter, strategies such as surface engineering, element doping, , loading cocatalyst, defect engineering, − and heterojunction have been developed to improve the photocatalytic efficiency.…”

Comprehensive analysis of NiFe2O4/MWCNTs nanocomposite to degrade a healthcare waste – tetracycline

“…9 These photocatalysts can degrade organic molecules when exposed to visible light, but they are constrained by their broad bandgap and low quantum efficiency. 9,10 Therefore, creating materials with outstanding photocatalytic efficiency and a robust sensitivity to visible light is crucial for breaking down organic contaminants in water. 11,12…”