Elsevier

Applied Surface Science

Volume 509, 15 April 2020, 145371
Applied Surface Science

Short Communication
Constructing Ni2P/Cd0.5Zn0.5S/Co3O4 ternary heterostructure for high-efficient photocatalytic hydrogen production

https://doi.org/10.1016/j.apsusc.2020.145371Get rights and content

Highlights

Abstract

Constructing heterostructure for efficient charge separation is a hopeful way for enhance photocatalytic hydrogen production. In this paper, we successfully construct the Ni2P/Cd0.5Zn0.5S/Co3O4 (Ni2P/CZS/Co3O4) heterostructure via three-step hydrothermal method. It is demonstrated that Ni2P/CZS/Co3O4 shows a prominent photocatalytic H2 generation activity of 39.66 mmol g−1 h−1, revealing about 2.42 times enhancement compared to that of the pure Cd0.5Zn0.5S (CZS) under visible light. The closely contacted CZS/Co3O4 forms a type-II heterostructure to accelerate the separation of photoinduced charge. The Ni2P acts as electron traps to capture the photoelectrons, and provide active sites for proton reduction. Moreover, the cooperative synergy of type-II heterostructure and active sites achieves an obvious improvement for photocatalytic hydrogen production.

Introduction

During last few decades, hydrogen (H2) has always been evoked as an ideal energy carrier owing to its high combustion efficiency and low pollutant generation [1], [2]. Recently, photocatalytic water splitting hydrogen production has attracted intensive attention [3]. CdS-based semiconductors, such as CZS, have been intensively studied due to their narrow band gap and band gap tunability [4], [5]. However, bulk CZS still suffer from fast recombination of photogenerated charge. Consequently, it is still a challenging task to exploit the suitable CZS based photocatalysts for hydrogen production [6], [7].

Tricobalt tetraoxide (Co3O4) is nontoxic p-type semiconductor, have been intensity studied due to its outstanding optical properties [8], [9], [10]. However, bare Co3O4 was inactive during the process of photocatalytic H2 evolution because the band position is improper for water splitting. Accordingly, several methods have already been made for water splitting, including element doping [11], and semiconductor coupling [12]. As we all know, p-n heterostructure possessing suitable band structures could enhance the photocatalytic performance. Construction of p-n heterostructure by coupling CZS and Co3O4 is a promising strategy to enhance their photocatalytic activity. Nevertheless, considering the low charge separation ability of p-n heterostructure, maximizing photocatalytic activity is difficult to achieve. Therefore, introducing cocatalysts to promote the separation of photoinduced carriers has been demonstrated to be an effective way to improve the photocatalytic activity of semiconductor [13]. To date, transition metal phosphides (including Cu3P, FeP, and Ni2P), have been proven as co-catalyst candidates due to their low cost and high conductivity for photocatalytic H2 production [14], [15]. Here in, we rationally design the noble-metal-free Ni2P/CZS/Co3O4 heterostructure based on three-step hydrothermal method. The photocatalytic performances of the Ni2P/CZS/Co3O4 were carefully analyzed under visible light irradiation. The influences of Ni2P and Co3O4 contents were investigated in details. In addition, a plausible photocatalytic mechanism was proposed.

Section snippets

Preparation of pure CZS

0.6663 g Cd(CH3COO)2·3H2O and 0.5488 g Zn(CH3COO)2·2H2O were dissolved in 20 mL of deionized water under vigorous stirring. Thereafter, 10 mL Na2S·9H2O (1.25 g) aqueous solution was slowly added into the above solution to obtain a yellow suspension. The suspension was transferred into a 50 mL Teflon stainless steel autoclave and heated at 200℃ for 12 h. The product was centrifuged, washed with ethanol and distilled water three times, and then dried in air at 60 °C for 12 h.

Preparation of Ni2P-x%/CZS composites

0.5 g of as-prepared

Results and discussion

XRD patterns of samples were shown in Fig. 1. Obviously, the diffraction peaks at 19°, 31.3°, 36.8°, 44.8°, 59.3° and 65.2° are attributed to the (1 1 1), (2 2 0), (3 1 1), (4 0 0), (5 1 1) and (4 4 0) planes of Co3O4, respectively. The peaks of the CZS are shifted toward higher-angle and side lower-angle, respectively, comparting with the patterns of pure hexagonal CdS and cubic ZnS, suggesting the formation of CZS solid solution rather than the CdS and ZnS simple mixing [16]. The peaks at

Conclusions

In this work, a novel noble-metal-free Ni2P/CZS/Co3O4 composite photocatalyst has been successfully fabricated via three hydrothermal method. The Ni2P/CZS/Co3O4 ternary heterostructure achieves the highest photocatalytic H2 production rate (39.66 mmol g−1 h−1), compared to CZS, Ni2P/CZS and CZS/Co3O4. In addition, the Ni2P-0.3%/CZS/Co3O4-1% photocatalyst also exhibits an excellent stability. The results demonstrate that CZS/Co3O4 heterostructure can accelerate the separation of photoinduced

CRediT authorship contribution statement

Tianpeng Yu: Conceptualization, Methodology, Data curation, Writing - original draft. Zihan Li: Visualization, Software, Investigation. Zunhang Lv: Visualization, Software, Investigation. Xin Liu: Visualization, Software, Investigation. Guixue Wang: Visualization, Software, Investigation. Guangwen Xie: Supervision, Validation, Resources. Luhua Jiang: Supervision, Validation, Resources.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The work was financially supported by the Taishan Scholar Program of Shandong (ts201712046) and the National Natural Science Foundation of China (Grant No.51672145).

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