Limits...
ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution.

Wu A, Jing L, Wang J, Qu Y, Xie Y, Jiang B, Tian C, Fu H - Sci Rep (2015)

Bottom Line: Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE.As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition.The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin 150080 (P. R. China).

ABSTRACT
The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

No MeSH data available.


(a) The energy band structure of ZnO/ZnS heter-junctions; (b) the schematic structure of ZnO-dotted ZnS; (c) the structure evolution from ZnO to PCMS.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4352920&req=5

f1: (a) The energy band structure of ZnO/ZnS heter-junctions; (b) the schematic structure of ZnO-dotted ZnS; (c) the structure evolution from ZnO to PCMS.

Mentions: ZnS is one of the important II-VI group semiconductors with promising application in the photocatalytic field. The energy gap of ZnS is 3.7 eV with a CB of −1.04 eV22, more negative than reduction potential of H+ to H2. So, ZnS is a suitable catalyst for PHE in principle. The studies have indicated the certain activity of ZnS for PHE, but the activity needs to be further enhanced by the assistance of Pt and Au2324. It is proposed to integrate ZnS with other materials to form a heterostructure for accelerating the separation of the photogenerated e−/h+ based on the virtues of the heterostructure. Zinc oxide (ZnO), another semiconductor containing Zn element, has a relatively positive position of conduction band (−0.31 eV) and valence band (2.89 eV) compared with ZnS. Thus, the combination of ZnO with ZnS is helpful to accelerate the separation of e−/h+ for improving the PHE activity due to their matched energy band (Figure 1a). Recent two works have demonstrated that the combination of ZnO and ZnS can catalyze hydrogen evolution even without Pt co-catalysts2526. However, the large size of both ZnS and ZnO in the composites can result in less contact of the catalyst with agents, thus not favorable for promoting the catalytic activity of the catalyst27. Especially, the origin of active catalytic sites for hydrogen evolution is not elucidated. Based on the principle of the heterogeneous catalysis, the activity will be largely enhanced by the high dispersion of ZnO on ZnS, typically, by the formation of ZnO-dotted ZnS. Therefore, it is designed and necessary to build a ZnO/ZnS heterjunction for highly effective, Pt-free PHE, and to elucidate the origin of active catalytic sites for hydrogen production.


ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution.

Wu A, Jing L, Wang J, Qu Y, Xie Y, Jiang B, Tian C, Fu H - Sci Rep (2015)

(a) The energy band structure of ZnO/ZnS heter-junctions; (b) the schematic structure of ZnO-dotted ZnS; (c) the structure evolution from ZnO to PCMS.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4352920&req=5

f1: (a) The energy band structure of ZnO/ZnS heter-junctions; (b) the schematic structure of ZnO-dotted ZnS; (c) the structure evolution from ZnO to PCMS.
Mentions: ZnS is one of the important II-VI group semiconductors with promising application in the photocatalytic field. The energy gap of ZnS is 3.7 eV with a CB of −1.04 eV22, more negative than reduction potential of H+ to H2. So, ZnS is a suitable catalyst for PHE in principle. The studies have indicated the certain activity of ZnS for PHE, but the activity needs to be further enhanced by the assistance of Pt and Au2324. It is proposed to integrate ZnS with other materials to form a heterostructure for accelerating the separation of the photogenerated e−/h+ based on the virtues of the heterostructure. Zinc oxide (ZnO), another semiconductor containing Zn element, has a relatively positive position of conduction band (−0.31 eV) and valence band (2.89 eV) compared with ZnS. Thus, the combination of ZnO with ZnS is helpful to accelerate the separation of e−/h+ for improving the PHE activity due to their matched energy band (Figure 1a). Recent two works have demonstrated that the combination of ZnO and ZnS can catalyze hydrogen evolution even without Pt co-catalysts2526. However, the large size of both ZnS and ZnO in the composites can result in less contact of the catalyst with agents, thus not favorable for promoting the catalytic activity of the catalyst27. Especially, the origin of active catalytic sites for hydrogen evolution is not elucidated. Based on the principle of the heterogeneous catalysis, the activity will be largely enhanced by the high dispersion of ZnO on ZnS, typically, by the formation of ZnO-dotted ZnS. Therefore, it is designed and necessary to build a ZnO/ZnS heterjunction for highly effective, Pt-free PHE, and to elucidate the origin of active catalytic sites for hydrogen production.

Bottom Line: Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE.As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition.The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin 150080 (P. R. China).

ABSTRACT
The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

No MeSH data available.