Efficient and Stable Photocatalytic Hydrogen Evolution Activity of Multi-Heterojunction Composite Photocatalysts: CdS and NiS2 Co-modified NaNbO3 Nanocubes.

Jingjing Xu,Jiawei Zhu,Junfeng Niu,Junpeng Yue,Mindong Chen

doi:10.3389/fchem.2019.00880

Abstract

In this study, a NaNbO3/CdS/NiS2 ternary composite photocatalyst containing no precious metals was successfully prepared by a simple hydrothermal method. The prepared ternary photocatalyst has a significant improvement in photocatalytic performance of hydrogen production from water splitting under visible light irradiation. The best sample NCN40% hydrogen production rate is 4.698 mmol g−1 h−1, which is about 24.7 times that of pure CdS sample. In addition, the stability of the composite catalyst in the long-term photocatalytic hydrogen production cycle is also improved. The reason for the enhanced hydrogen production performance may be the optimization of the microstructure of the catalyst and the reduction of photogenerated electron-hole recombination. The construction of multi-heterojunctions (NaNbO3-CdS, CdS–NiS2, and NaNbO3-NiS2) helps to reduce the recombination of carriers. Furthermore, the in-situ-formed NiS2 nanoparticles can serve as active sites for hydrogen evolution. All of these factors induced the improved photocatalytic activity of the as-prepared ternary photocatalyst.

Highlights

Hydrogen is regarded as the clean energy with the greatest development potential in the twentyfirst century, with the advantages of high calorific value and no pollution (Esswein and Nocera, 2007; Dempsey et al, 2009; Wang et al, 2018; Mu et al, 2020a)
NaNbO3 has the advantages of redox ability due to large band gap, it has disadvantages like low charge separation efficiency and low photocatalytic activity (Xu et al, 2015)
Characteristic diffraction peaks of CdS and NaNbO3 were found in NC40% and NCN40% composites simultaneously, indicating the successful preparation of the target samples

Summary

INTRODUCTION

Hydrogen is regarded as the clean energy with the greatest development potential in the twentyfirst century, with the advantages of high calorific value and no pollution (Esswein and Nocera, 2007; Dempsey et al, 2009; Wang et al, 2018; Mu et al, 2020a). The as-synthesized NCN40% sample had a photocatalytic hydrogen evolution rate of 4.699 mmol g−1 h−1, which had great improvement compared to pure CdS. NaNbO3 itself has excellent electrical conductivity and chemical stability It acts as a carrier for CdS to increase the reaction surface with water and forms a heterojunction with CdS, which can improve light irradiation stability and accelerate charge separation (Al Balushi et al, 2018). For the preparation of NaNbO3/CdS-40% (NC40%), NaNbO3 (0.7224 g) was added into pure water (150 ml) and ultrasonically treated for 30 min to disperse entirely. A total of 25 mg of the photocatalyst, pure water (50 ml), and lactic acid (4 ml) were added into a glass reactor, and the suspension was ultrasonicated and stirred for 5 min for dispersion. The visible light source was a 300-W xenon lamp with a 400-nm filter, and room temperature was maintained at 25◦C

RESULTS AND DISCUSSION

CONCLUSIONS

DATA AVAILABILITY STATEMENT