Noble-metal-free carbon nanotube-Cd0.1Zn0.9S composites for high visible-light photocatalytic H2-production performance

Abstract

Visible light photocatalytic H(2) production from water splitting using solar light is of great importance from the viewpoint of solar energy conversion and storage. In this study, a novel visible-light-driven photocatalyst multiwalled carbon nanotube modified Cd(0.1)Zn(0.9)S solid solution (CNT/Cd(0.1)Zn(0.9)S) was prepared by a simple hydrothermal method. The prepared samples exhibited enhanced photocatalytic H(2)-production activity under visible light. CNT content had a great influence on photocatalytic activity and an optimum amount of CNT was determined to be ca. 0.25 wt%, at which the CNT/Cd(0.1)Zn(0.9)S displayed the highest photocatalytic activity under visible light, giving an H(2)-production rate of 78.2 μmol h(-1) with an apparent quantum efficiency (QE) of 7.9% at 420 nm, even without any noble metal cocatalysts, exceeding that of pure Cd(0.1)Zn(0.9)S by more than 3.3 times. The enhanced photocatalytic activity was due to CNT as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. Furthermore, the prepared sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our findings demonstrated that CNT/Cd(0.1)Zn(0.9)S composites were a promising candidate for the development of high-performance photocatalysts in photocatalytic H(2) production. This work not only shows a possibility for the utilization of low cost CNT as a substitute for noble metals (such as Pt) in the photocatalytic H(2)-production but also for the first time shows a significant enhancement in the H(2)-production activity by using metal-free carbon materials as effective co-catalysts.

Enhanced Visible‐Light Photocatalytic H2 Production by ZnxCd1−xS Modified with Earth‐Abundant Nickel‐Based Cocatalysts

“…Remarkably, a very high quantum efficiency (QE) of 29.5 % at 420 nm is achieved by Ni(OH) 2 -ZCS, which represents one of the most efficient metal sulfide photocatalysts without the assistance of noblemetal co-catalysts to date. [5,11,17,18,21,22] This result shows clearly that Ni(OH) 2 could be a substitute for Pt as a highly efficient, low-cost co-catalyst. However, NiO, which has been applied successfully as a powerful co-catalyst on many photocatalysts to promote H 2 evolution, [26,29] deactivated the photocatalytic activity of ZCS and reduced its H 2 -production rate to only 117 mmol h À1 g…”

“…[13,14] However, only a few studies have focused on the integration of Zn x Cd 1Àx S with an earthabundant and inexpensive co-catalyst as a substitute for a Pt co-catalyst to achieve highly efficient photocatalytic H 2 production. [11,[20][21][22][23] In recent years, co-catalysts composed of earth-abundant elements have been explored aggressively to replace Pt as the extreme scarcity and high price of Pt restricts the massive application of photocatalysts such as Zn x Cd 1Àx S for large-scale solar H 2 production. [24] Especially, materials based on Ni, such as Ni, [25,26] NiS, [27,28] NiO, [26,[29][30][31] and Ni(OH) 2 , [5,32,33] are among the most active co-catalysts loaded on various semiconductor photocatalysts to achieve highly efficient and cost-effective photocatalytic H 2 production.…”

Design and fabrication of semiconductor photocatalyst for photocatalytic reduction of CO2 to solar fuel

“…CNT possesses many unique properties such as a large electron-storage capacity, good electron conductivity, good chemical stability, excellent mechanical strength, a large specific surface area (> 150 m 2 g −1 ), and mesoporous character which favors the diffusion of reacting species [224][225][226]. Consequently, as a good support for semiconductors, CNT has been widely used to construct semiconductor-CNT nanocomposite photocatalysts in the past few years [227,228]. However, there are very restricted reports on semiconductor-CNT nanocomposite photocatalysts for photocatalytic CO 2 reduction.…”

Enhanced Photocatalytic Hydrogen‐Production Performance of Graphene–ZnxCd1−xS Composites by Using an Organic S Source

“…This is because graphene in the composite has high electrical conductivity and high electron-storage capacity and can thus act as an effective electron sink to trap electrons, which are then released and participate in the H 2 -production reaction. [64,65] However, a further increase in the graphene content led to a dramatic deterioration of the photocatalytic performance. In particular, at a graphene content of 5.0 % (5.0G-ZCS), the H 2 -production rate decreased to 0.42 mmol h À1 g À1 .…”