Fabrication of hierarchical ZnO/CdS heterostructured nanocomposites for enhanced hydrogen evolution from solar water splitting

Abstract

ZnO/CdS heterostructured nanocomposites were fabricated with enhanced light harvesting capability and photostability using sequential sonochemical and hydrothermal methods from ZnO rods and particles. Interestingly, in the composite made up of CdS sensitized ZnO rods, both ZnO and CdS exist in the hexagonal wurtzite form with different morphologies. On the other hand, in the composite made up of CdS sensitized ZnO particles, ZnO exists in the hexagonal wurtzite form, whereas CdS in the cubic form but with a similar morphology. The synthesized photocatalysts under simulated solar irradiation exhibited hydrogen evolution rates of 870 and 1007 μmol h(-1) g(-1) for the ZnO rod/CdS and ZnO nanoparticle/CdS composites, respectively, compared to the native ZnO (40 μmol h(-1) g(-1) for rods and 154 μmol h(-1) g(-1) for particles) and CdS (208 μmol h(-1) g(-1)) structures. The apparent quantum yield of CdS was only 1.2%, whereas the composites exhibited much higher quantum yields of 4.9% and 5.7%. Our results confirmed that the morphology of the host matrix ZnO played a crucial role in forming ZnO/CdS heterostructures with improved interface for the direct Z-scheme mechanism with enhanced hydrogen evolution efficiency.

A Review of Direct Z‐Scheme Photocatalysts

“…For example, Mukhopadhyay et al reported hierarchical ZnO/CdS nanocomposites with enhanced photocatalytic water‐splitting performance . ZnO nanorods and mesoporous ZnO nanoflowers were firstly prepared through sequential sonochemical and hydrothermal methods.…”

“…For example, Mukhopadhyay et al reported hierarchical ZnO/CdS nanocomposites with enhanced photocatalytic water splitting performance. [59] ZnO nanorods and mesoporous ZnO nanoflowers were firstly prepared through sequential sono chemical and hydrothermal methods. Then, the prepared ZnO nanorods and mesoporous ZnO nanoflowers were coupled with CdS NPs to form ZC1 and ZC2 direct Zscheme photo catalysts, respectively (Figure 18a-d).…”

A prototype reactor for highly selective solar-driven CO2reduction to synthesis gas using nanosized earth-abundant catalysts and silicon photovoltaics

“…Enhanced H 2 production through the decoration of ZnO nanoparticles has already been observed for ZnS and CdS nanocomposites as well. 46,47…”

Enhanced hydrogen evolution from water splitting based on ZnO nanosheet/CdS nanoparticle heterostructures

“…Previous literatures have reported the syntheses of ZnO and CdS heterostructures to form respective hybrid systems, which are used to improve the efficiency of hydrogen production and stability. [24][25][26] For instance, X. W. Wang , which is 13 and 138 times higher than that of single ZnO. 3 S. Mukhopadhyay et al prepared disk ZnO by an ultrasonic chemical method, then deposited CdS nanoparticles on the disk surface using a hydrothermal method.…”

“…The hydrogen production efficiency of the composite was 22 times higher than that of single ZnO in visible light. 26 Although these results of the above works are promising, the synthesis of ZnO/CdS heterostructures requires high temperatures and complex preparation methods, which are energy-consuming procedures.…”