Highly Efficient Photocatalyst Based on a CdS Quantum Dots/ZnO Nanosheets 0D/2D Heterojunction for Hydrogen Evolution from Water Splitting

Abstract

A novel CdS/ZnO heterojunction constructed of zero-dimensional (0D) CdS quantum dots (QDs) and two-dimensional (2D) ZnO nanosheets (NSs) was rationally designed for the first time. The 2D ZnO NSs were assembled into ZnO microflowers (MFs) via an ultrasonic-assisted hydrothermal procedure (100 °C, 12 h) in the presence of a NaOH solution (0.06 M), and CdS QDs were deposited on both sides of every ZnO NS in situ by using the successive ionic-layer absorption and reaction method. It was found that the ultrasonic treatment played an important role in the generation of ZnO NSs, while NaOH was responsible to the assembly of a flower-like structure. The obtained CdS/ZnO 0D/2D heterostructures exhibited remarkably enhanced photocatalytic activity for hydrogen evolution from water splitting in comparison with other CdS/ZnO heterostructures with different dimensional combinations such as 2D/2D, 0D/three-dimensional (3D), and 3D/0D. Among them, CdS/ZnO-12 (12 deposition cycles of CdS QDs) exhibited the highest hydrogen evolution rate of 22.12 mmol/g/h, which was 13 and 138 times higher than those of single CdS (1.68 mmol/g/h) and ZnO (0.16 mmol/g/h), respectively. The enhanced photocatalytic activity can be attributed to several positive factors, such as the formation of a Z-scheme photocatalytic system, the tiny size effect of 0D CdS QDs and 2D ZnO NSs, and the intimate contact between CdS QDs and ZnO NSs. The formation of a Z-scheme photocatalytic system remarkably promoted the separation and migration of photogenerated electron-hole pairs. The tiny size effect effectively decreased the recombination probability of electrons and holes. The intimate contact between the two semiconductors efficiently reduced the migration resistance of photogenerated carriers. Furthermore, CdS/ZnO-12 also presented excellent stability for photocatalytic hydrogen evolution without any decay within five cycles in 25 h.

Metal Nanoclusters: New Paradigm in Catalysis for Water Splitting, Solar and Chemical Energy Conversion

“…For photoinduced water splitting, semiconductors such as TiO 2 , ZnO have been studied extensively . But corrosion of these catalysts, recombination of charges, and the wide band gap of such materials decreases their stability.…”

“…For photoinduced water splitting, semiconductors such as TiO 2 , ZnO have been studied extensively. [201,202] But corrosion of these catalysts, recombination of charges, and the wide band gap of such materials decreases their stability.T oo vercome these problems, mostly NPs of noble metals (Au, Ag, and Pd) have been used. [203][204][205] In addition, the efficiency of these catalysts can be improved by using small-and monodisperse metal NPs as aco-catalyst to increasethe lifetimeofseparated charges and achieve good compatibility with the band gap of the semiconductors.…”

Structure and Band Alignment Engineering of CdS/TiO2/Bi2WO6 Trilayer Nanoflake Array for Efficient Photoelectrochemical Water Splitting

“…[31][32][33][34][35][36][37][38] In such geometry, semiconductors with large specific surface area and high conductivity usually serve as host skeletons, while the narrow band gap semiconductors with high visible light absorption coefficient coat on the host skeleton surface as guest materials. [31][32][33][34][35][36][37][38] In such geometry, semiconductors with large specific surface area and high conductivity usually serve as host skeletons, while the narrow band gap semiconductors with high visible light absorption coefficient coat on the host skeleton surface as guest materials.…”

Magnetically Separable Fe3O4@CdS Type‐II Nanohybrids with Excellent Photocatalytic Activity and Antibacterial Properties

“…Moreover, single‐phase CdS QDs are not photostable and photocorrosion may take place during photocatalysis. Diverse approaches implemented to overcome these issues include forming a heterostructure of CdS QDs with other semiconductors, polymers, and/or surface loading of noble‐metal cocatalysts . Kandi et al.…”

“…Moreover,s ingle-phase CdS QDs are not photostable and photocorrosion may take place during photocatalysis. Diverse approaches implemented to overcome these issues include formingaheterostructure of CdS QDs with other semiconductors, [8][9][10] polymers, [11] and/or surfacel oading of noble-metalc ocatalysts. [12][13][14] Kandi et al reported the synthesis of CdS QD/BiOI composites to study their photocatalytic activities for rhodamine Bd egradation and hydrogen production under solar-and visible-light irradiation, respectively.…”