Precise Tuning of Bilayer Ultrasmall MoS2 Featuring Inhibition of Carrier Recombination and Fast Surface Chemistry for Green H2 Evolution.

Achieving water splitting to produce green H2 , using the noble-metal-free MoS2 , has attracted huge interest from researchers. However, tuning the number of MoS2 layers precisely while obtaining small lateral sizes to surge the H2 -evolution rate is a tremendous challenge. Here, a bottom-up strategy is designed for the in situ growth of ultrasmall lateral-sized MoS2 with tunable layers on CdS nanorods (CN) by controlling the decomposition temperature and concentration of substrate seed (NH4 )2 MoS4 . Here, the bilayer MoS2 and CN coupling (2L-MoS2 /CN) exhibits the optimum photocatalytic activity. Compared to thicker MoS2 , the 2L-MoS2 has sufficient reduction capacity to drive photocatalytic H2 evolution and the ultrasmall lateral size provides more active sites. Meanwhile, the indirect bandgap, in contrast to the direct bandgap of the monolayer MoS2 , suppresses the carrier recombination transferred to 2L-MoS2 . Under the synergistic effect of both, 2L-MoS2 /CN has fast surface chemical reactions, resulting in the photocatalytic H2 -evolution rate of up to 41.86 mmol g-1 h-1 . A novel strategy is provided here for tuning the MoS2 layers to achieve efficient H2 evolution.

In Situ Construction of BiO(ClBr)(1-x)/2Ix-n Solid Solution with Appropriate Surface Iodine Vacancies for Synergistically Boosting Visible-Light Photo-Oxidation Capability.

A proposed BiO(ClBr)(1-x)/2Ix-n solid solution containing abundant iodine vacancies has been constructed through a facile solvothermal treatment strategy. Fascinatingly, the iodine-vacancy BiO(ClBr)(1-x)/2Ix-n solid solution exhibits an outstanding visible-light photocatalytic degradation property for the environmentally hazardous pollutants of methyl orange, tetracycline, and phenol solutions, which is credited to the synergistic effect of iodine vacancies and the solid solution. By manipulating the molar ratios of Cl, Br, and I, the band structure of the solid solution attained is controlled, enabling the samples to maximize the harvest of visible light and to possess strong oxidation features. More importantly, the construction of iodine vacancies is bound to modulate the local surface atomic structure and promotes the efficiency of the separation of photogenerated carriers. Given these, the microstructure and physicochemical and photoelectrochemical properties of the photocatalysts are fully characterized in a series. In addition, the iodine-vacancy BiO(ClBr)(1-x)/2Ix-n solid solution has a stable crystal structure that permits favorable recyclability even after multiple cycles of degradation. This study sheds light on the significance of the simultaneous existence of vacancy and the solid solution for the enhanced performance of photocatalysts and opens up new insights for sustainable solar-chemical energy conversion.

Cadmium Sulfide 3D Photonic Crystal with Hierarchically Ordered Macropores for Highly Efficient Photocatalytic Hydrogen Generation.

Cadmium sulfide is a potential candidate for photocatalytic water splitting. However, CdS nanoparticles have a high recombination rate of photoinduced carriers induced by aggregation. Therefore, decreasing the recombination rate and increasing the migration rate of photogenerated carriers are essential to drive the development and application of CdS in hydrogen production. In this study, we design CdS with a three-dimensional ordered macroporous (3DOM) structure using polymethylmethacrylate as a template. It not only retains the excellent visible light response of CdS but also improves the easy recombination of photogenerated carriers in CdS nanoparticles by taking advantage of the unique ability of mass transfer, charge separation, and migration in the 3DOM structure. Meanwhile, the highly ordered periodic structure of 3DOM CdS can produce a slow photon effect of photonic crystals to obtain more photoinduced carriers. In particular, we found that a suitable stop-band position is beneficial to maximize the utilization of the slow photon effect. The photocatalytic hydrogen evolution rate of Pt-CdS is considerably improved after constructing the 3DOM structure. This study provides a new design strategy of ordered macroporous sulfide catalysts to achieve high photocatalytic activity.

Indirect Substitution Constructing Halogen-Vacancy BiOCl1-xIn Solid Solution with a Suitable Surface Structure for Enhanced Photoredox Performance.

Photocatalytic technology has made a series of breakthroughs in environmental remediation, but the degradation performance of persistent heavy metal ions and organic pollutants is not particularly excellent. In addition, the layered structure of bismuth oxyhalides (BiOX, X = I, Br, and Cl) has been a popular material for photodegradation and photoelectrochemistry. Accordingly, with a view to construct a suitable band structure and control the surface structure, it is necessary to develop a strategy to synthesize a BiOCl1-xIn solid solution with halogen vacancies. In this study, halogen vacancies are in situ introduced into the BiOCl1-xIn solid solution through constructing chemical bonds between the hydroxyl groups in glycerol and the I ions during the growth process. The band of the halogen-vacancy BiOCl1-xIn solid solution is widened and active sites centered at halogen vacancies are formed in the direction favorable for the photocatalytic reaction, resulting in enhanced performance in the reduction of Cr(VI) and the oxidation of phenol. The results obtained can provide a new idea for the design of efficient photocatalysts by controlling the formation of halogen vacancies.

Interfacial elaborating In2O3-decorated ZnO/reduced graphene oxide/ZnS heterostructure with robust internal electric field for efficient solar-driven hydrogen evolution.

Solar-driven hydrogen evolution over ZnO-ZnS heterostructures is considered as a promising strategy for sustainable-energy issues. However, the industrialization of this strategy is still constrained by suppressed carrier migration, rapid charge recombination, and the inevitable utilization of noble-metal particles. Herein, we envision a novel strategy of successfully introducing In2O3 into the ZnO-ZnS heterostructure. Benefiting from the optimized internal electric field and the charge carrier migration mode based on the direct Z-scheme, the interfacial elaborating In2O3-decorated ZnO/reduced graphene oxide (rGO)/ZnS heterostructure manifests smooth charge migration, suppressed electron-hole pair recombination, and increased surface active sites. More importantly, the in situ introduction of In2O3 optimizes the construction of the internal electric field, favoring directional light-triggered carrier migration. As a result, the light-induced electrons generated from the heterostructure can be efficiently employed for the hydrogen evolution reaction. Hence, this work would shed light on the in situ fabrication of noble-metal-free photocatalysts for solar-driven water splitting.

Three-dimensionally ordered Macroporous perovskite sodium tantalum for robust hydrogen and hydrogen peroxide production.

Constructing photocatalytic materials into three-dimensionally ordered macroporous (3DOM) is considered an effective strategy for improving mass transfer behaviors and shortening the electron migration path. However, this strategy is challenging for ternary semiconductors because they cannot be directly synthesized by traditional thermal decomposition methods. Ternary systems need to face the structural instability caused by the construction of macroporous morphology, which limits the application of the ordered macroporous structure. In this work, we designed a novel and efficient two-step crystal nucleation strategy for constructing a highly stable ternary ordered macroporous structure. Here, 3DOM NaTaO3 was reported as a promising candidate. Compared with nonporous NaTaO3, which has no catalytic activity in pure water, 807.9 and 280.1 µmol g-1h-1 of H2 and H2O2 production rates were first achieved on the 3DOM NaTaO3. Furthermore, the rate of photocatalytic H2 evolution over the 3DOM NaTaO3 improved sharply to 3.9 mmol g-1h-1 in methanol aqueous solution, which was 139 times that of nonporous NaTaO3. The construction of 3DOM NaTaO3 enables the participation of the bulk interior in photochemical reaction and provides more options for later decoration. This work opens a new door for constructing more 3DOM ternary semiconductors for catalytic reactions.