Photocatalytic Activity of S-Scheme Heterostructure for Hydrogen Production and Organic Pollutant Removal: A Mini-Review

Abstract

Finding new technologies and materials that provide real alternatives to the environmental and energy-related issues represents a key point on the future sustainability of the industrial activities and society development. The water contamination represents an important problem considering that the quantity and complexity of organic pollutant (such as dyes, pesticides, pharmaceutical active compounds, etc.) molecules can not be efficiently addressed by the traditional wastewater treatments. The use of fossil fuels presents two major disadvantages: (1) environmental pollution and (2) limited stock, which inevitably causes the energy shortage in various countries. A possible answer to the above issues is represented by the photocatalytic technology based on S-scheme heterostructures characterized by the use of light energy in order to degrade organic pollutants or to split the water molecule into its components. The present mini-review aims to outline the most recent achievements in the production and optimization of S-scheme heterostructures for photocatalytic applications. The paper focuses on the influence of heterostructure components and photocatalytic parameters (photocatalyst dosage, light spectra and intensity, irradiation time) on the pollutant removal efficiency and hydrogen evolution rate. Additionally, based on the systematic evaluation of the reported results, several perspectives regarding the future of S-scheme heterostructures were included.

H2-production and electron-transfer mechanism of a noble-metal-free WO3@ZnIn2S4 S-scheme heterojunction photocatalyst

“…Recently, an emerging S-scheme heterojunction has been proposed, which usually consists of both oxidation and reduction photocatalysts. [26][27][28][29][30][31][32][33] The useless photogenerated electrons and holes in the S-scheme heterojunction recombine, while the useful electrons in the reduction photocatalyst CB and holes in the oxidation photocatalyst valence band (VB) are preserved to participate in photocatalytic reactions. Such a transfer pathway of charge carriers facilitates efficient electron/hole separation and also enables stronger redox capability of the surviving photocarriers.…”

Main Hydrogen Production Processes: An Overview

“…In the last years different configurations have been proposed, including CuS-and NiS-based heterojunctions, titanium dioxide based core-shell structures and periodical structures with excellent adsorption ability, and imogolite hollow cylinders [90], as well as S-scheme heterostructure [91]. Among them, the titanium dioxide based ones are the most interesting, due to the chemical resistance properties, accessibility, and affordability [92].…”

Rational Construction of a 0D/1D S-Scheme CeO2/CdWO4 Heterojunction for Photocatalytic CO2 Reduction and H2 Production

“…In such hybrid systems, the separation of photoinduced charge carriers follows different pathways, among which the S-scheme model has been proven to be the most effective one . In the S-scheme heterojunction, electrons with more positive potential recombine with the holes possessing more negative potential, resulting in a heterojunction photocatalyst with a higher redox ability . Also, the presence of two desired semiconductors with useful optical and structural properties enables the heterojunction to absorb a broader range of irradiated light as well as improve the physical adsorption of reactant molecules, which accelerates the rate of photocatalytic reactions. − In this regard, various CdWO 4 -based heterojunctions were fabricated and applied for the photocatalytic production of solar fuels.…”