CdS@MoS2异质结催化剂可见光光催化产氢和选择性氧化苯甲醇的耦合反应

Visible-light-driven photocatalytic hydrogen production coupled with selective oxidation of benzyl alcohol over CdS@MoS2 heterostructures

光催化产氢,并同时选择性氧化有机底物、生产高附加值精细化学品,引起了科学家的广泛关注.在本文中,我们报道了一种无贵金属的Cd S@Mo S2异质结光催化剂,在可见光下可以高效地产氢并同时将苯甲醇选择性氧化为苯甲醛.在0.3 mmol苯甲醇底物的条件下,Cd S@Mo S2能够产生4233μmol g^-1h^-1的氢气,比纯的Cd S纳米棒高约53倍,并且苯甲醇选择性氧化为苯甲醛具有很高的选择性;当苯甲醇增加到1.0 m m o l时,产生氢气的量高达9033μmol g^-1h^-1.通过扫描电子显微镜和透射电子显微镜图像表征,发现p型Mo S2具有花状结构并紧密粘附在n型Cd S半导体纳米棒上,从而形成p-n异质结.作为潜在的Z型光催化剂,Cd S@Mo S2异质结催化剂在可见光下有效地产生和分离电子-空穴对,其中电子用于还原以产生氢气,而空穴则将苯甲醇氧化为苯甲醛.此外,我们提出了光生电荷转移和分离的机理,并通过荧光光谱、电化学阻抗谱、光电流和莫特-肖特基测量进行了验证.结果表明,Cd S@Mo S2异质结具有快速的电荷分离和转移效率,极大地提高了苯甲醇的脱氢性能.这项工作为高性能Z型光催化剂的合理设计,以及利用空穴和电子同时获得两种有价值的化学物质提供了思路.

Photocatalytic hydrogen production coupled with selective oxidation of organic substrates to produce highvalue-added fine chemicals has drawn increasing attention.Herein,we report a noble metal-free photocatalyst for the highly efficient and simultaneous generation of hydrogen and the selective oxidation of benzyl alcohol into benzaldehyde over Cd S@Mo S2 heterostructures under visible light.Without the need for a sacrificial agent,Cd S@Mo S2 displayed an excellent hydrogen production rate of 4233μmol g^-1h^-1with0.3 mmol benzyl alcohol,which is approximately 53 times higher than that of bare Cd S nanorods(80μmol g^-1h^-1).The reaction system was highly selective for the oxidation of benzyl alcohol into benzaldehyde.When the amount of benzyl alcohol increased to 1.0 mmol,the hydrogen production reached9033μmol g^-1h^-1.Scanning electron microscopy and transmission electron microscopy images revealed that p-type Mo S2 sheets with a flower-like structure closely adhered to n-type semiconductor Cd S nanorods through the formation of a p-n heterojunction.As a potential Z-scheme photocatalyst,the Cd S@Mo S2 heterostructure effectively produces and separates electron-hole pairs under visible light.Thus,the electrons are used for reduction to generate hydrogen,and the holes oxidize benzyl alcohol into benzaldehyde.Moreover,a mechanism of photogenerated charge transfer and separation was proposed and verified by photoluminescence,electrochemical impedance spectroscopy,photocurrent and Mott-Schottky measurements.The results reveal that the Cd S@Mo S2 heterojunctions have rapid and efficient charge separation and transfer,thereby greatly improving benzyl alcohol dehydrogenation.This work provides insight into the rational design of high-performance Z-scheme photocatalysts and the use of holes and electrons to obtain two valuable chemicals simultaneously.