Self-surface charge exfoliation and electrostatically coordinated 2D hetero-layered hybrids

MoS2 Quantum Dot Growth Induced by S Vacancies in a ZnIn2S4 Monolayer: Atomic-Level Heterostructure for Photocatalytic Hydrogen Production

It is highly demanded to steer the charge flow in photocatalysts for efficient photocatalytic hydrogen reactions (PHRs). In this study, we developed a smart strategy to position MoS₂ quantum dots (QDs) at the S vacancies on a Zn facet in monolayered ZnIn₂S₄ (Vs-M-ZnIn₂S₄) to craft a two-dimensional (2D) atomic-level heterostructure (MoS₂QDs@Vs-M-ZnIn₂S₄). The electronic structure calculations indicated that the positive charge density of the Zn atom around the sulfur vacancy (Vs) was more intensive than other Zn atoms. The Vs confined in monolayered ZnIn₂S₄ established an important link between the electronic manipulation and activities of ZnIn₂S₄. The Vs acted as electron traps, prevented vertical transmission of electrons, and enriched electrons onto the Zn facet. The Vs-induced atomic-level heterostructure sewed up vacancy structures of Vs-M-ZnIn₂S₄, resulting in a highly efficient interface with low edge contact resistance. Photogenerated electrons could quickly migrate to MoS₂QDs through the intimate Zn-S bond interfaces. As a result, MoS₂QDs@Vs-M-ZnIn₂S₄ showed a high PHR activity of 6.884 mmol g^-1 h^-1, which was 11 times higher than 0.623 mmol g^-1 h^-1 for bulk ZnIn₂S₄, and the apparent quantum efficiency reached as high as 63.87% (420 nm). This work provides a prototype material for looking into the role of vacancies between electronic structures and activities in 2D photocatalytic materials and gives insights into PHR systems at the atomic level.

MOF-derived porous Fe2O3 with controllable shapes and improved catalytic activities in H2S selective oxidation

Porous Fe₂O₃ architectures with controllable shapes are synthesized by the MOF-template method and show excellent catalytic activity for H₂S selective oxidation.

Engineering graphene and TMDs based van der Waals heterostructures for photovoltaic and photoelectrochemical solar energy conversion

This review provides a systematic overview of the integration, surface, and interfacial engineering of 2D/3D and 2D/2D homo/heterojunctions for PV and PEC applications.

Unique physicochemical properties of two-dimensional light absorbers facilitating photocatalysis

The emergence of two-dimensional (2D) materials with a large lateral size and extremely small thickness has significantly changed the development of many research areas by producing a variety of unusual physicochemical properties.

Ultrathin 2D Photocatalysts: Electronic-Structure Tailoring, Hybridization, and Applications

As a sustainable technology, semiconductor photocatalysis has attracted considerable interest in the past several decades owing to the potential to relieve or resolve energy and environmental-pollution issues. By virtue of their unique structural and electronic properties, emerging ultrathin 2D materials with appropriate band structure show enormous potential to achieve efficient photocatalytic performance. Here, the state-of-the-art progress on ultrathin 2D photocatalysts is reviewed and a critical appraisal of the classification, controllable synthesis, and formation mechanism of ultrathin 2D photocatalysts is presented. Then, different strategies to tailor the electronic structure of ultrathin 2D photocatalysts are summarized, including component tuning, thickness tuning, doping, and defect engineering. Hybridization with the introduction of a foreign component and maintaining the ultrathin 2D structure is presented to further boost the photocatalytic performance, such as quantum dots/2D materials, single atoms/2D materials, molecular/2D materials, and 2D-2D stacking materials. More importantly, the advancement of versatile photocatalytic applications of ultrathin 2D photocatalysts in the fields of water oxidation, hydrogen evolution, CO₂ reduction, nitrogen fixation, organic syntheses, and removal pollutants is discussed. Finally, the future opportunities and challenges regarding ultrathin 2D photocatalysts to bring about new opportunities for future research in the field of photocatalysis are also presented.

Multichannel Charge Transfer and Mechanistic Insight in Metal Decorated 2D-2D Bi2 WO6 -TiO2 Cascade with Enhanced Photocatalytic Performance

Promising semiconductor-based photocatalysis toward achieving efficient solar-to-chemical energy conversion is an ideal strategy in response to the growing worldwide energy crisis, which however is often practically limited by the insufficient photoinduced charge-carrier separation. Here, a rational cascade engineering of Au nanoparticles (NPs) decorated 2D/2D Bi₂ WO₆ -TiO₂ (B-T) binanosheets to foster the photocatalytic efficiency through the manipulated flow of multichannel-enhanced charge-carrier separation and transfer is reported. Mechanistic characterizations and control experiments, in combination with comparative studies over plasmonic Au/Ag NPs and nonplasmonic Pt NPs decorated 2D/2D B-T composites, together demonstrate the cooperative synergy effect of multiple charge-carrier transfer channels in such binanosheets-based ternary composites, including Z-scheme charge transfer, "electron sink," and surface plasmon resonance effect, which integratively leads to the boosted photocatalytic performance.

Hierarchical ZnIn2 S4 /MoSe2 Nanoarchitectures for Efficient Noble-Metal-Free Photocatalytic Hydrogen Evolution under Visible Light

A highly efficient visible-light-driven photocatalyst is urgently necessary for photocatalytic hydrogen generation through water splitting. Herein, ZnIn₂ S₄ hierarchical architectures assembled as ultrathin nanosheets were synthesized by a facile one-pot polyol approach. Subsequently, the two-dimensional-network-like MoSe₂ was successfully hybridized with ZnIn₂ S₄ by taking advantage of their analogous intrinsic layered morphologies. The noble-metal-free ZnIn₂ S₄ /MoSe₂ heterostructures show enhanced photocatalytic H₂ evolution compared to pure ZnIn₂ S₄ . It is noteworthy that the optimum nanocomposite of ZnIn₂ S₄ /2 % MoSe₂ photocatalyst displays a high H₂ generation rate of 2228 μmol g^-1  h^-1 and an apparent quantum yield (AQY) of 21.39 % at 420 nm. This study presents an unprecedented ZnIn₂ S₄ /MoSe₂ metal-sulfide-metal-selenide hybrid system for H₂ evolution. Importantly, the present efficient hybridization strategy reveals the potential of hierarchical nanoarchitectures for a multitude of energy storage and solar energy conversion applications.

In-situ synthesis of amorphous silver silicate/carbonate composites for selective visible-light photocatalytic decomposition

Coupling two different semiconductors to form composite photocatalysts is an extremely significant technique for environmental remediation. Here, a one-step in-situ precipitation method has been developed to prepare amorphous silver silicate/carbonate (AgSiO/Ag₂CO₃) nanoparticles (NPs) composites, which are well dispersed sphere-like particles with the sizes of around ~50–100 nm. The high-efficiency photocatalytic activities under visible light (VL) have been carefully evaluated, and the AgSiO/Ag₂CO₃ NPs composites exhibit selective photocatalytic degradations on Methylene Blue (MB) and Rhodamine B (RhB). The maximum degradation rate for MB can reach ~99.1% within ~40 min under VL irradiation, much higher than that of RhB (~12%) in the same condition, which can be ascribed to (I) the smaller molecule size of MB than that of RhB, (II) the fast charge separation between AgSiO NPs and Ag₂CO₃ NPs, abundant heterojunction interfaces as well as fully exposed reactive sites. These composites are proposed to be an example for the preparation of other silicate composite photocatalysts for practical applications in environmental remediation.

An unsaturated metal site-promoted approach to construct strongly coupled noble metal/HNb3O8 nanosheets for efficient thermo/photo-catalytic reduction

Creating two-dimensional (2D) crystal-metal heterostructures with an ultrathin thickness has spurred increasing research endeavors in catalysis because of its fascinating opportunities in tuning the electronic state at the surface and enhancing the chemical reactivity. Here we report a novel and facile Nb⁴⁺-assisted strategy for the in situ growth of highly dispersed Pd nanoparticles (NPs) on monolayer HNb₃O₈ nanosheets (HNb₃O₈ NS) constituting a 2D Pd/HNb₃O₈ NS heterostructure composite without using extra reducing agents and stabilizing agents. The Pd NP formation is directed via a redox reaction between an oxidative Pd salt precursor (H₂PdCl₄) and reductive unsaturated surface metal (Nb⁴⁺) sites induced by light irradiation on monolayer HNb₃O₈ NS. The periodic arrangement of metal Nb nodes on HNb₃O₈ NS leads to a homogeneous distribution of Pd NPs. Density functional theory (DFT) calculations reveal that the direct redox reaction between the Nb⁴⁺ and Pd²⁺ ions leads to a strong chemical interaction between the formed Pd metal NPs and the monolayer HNb₃O₈ support. Consequently, the as-obtained Pd/HNb₃O₈ composite serves as a highly efficient bifunctional catalyst in both heterogeneous thermocatalytic and photocatalytic selective reduction of aromatic nitro compounds in water under ambient conditions. The achieved high activity originates from the unique 2D nanosheet configuration and in situ Pd incorporation, which leads to a large active surface area, strong metal-support interaction and enhanced charge transport capability. Moreover, this facile Nb⁴⁺-assisted synthetic route has demonstrated to be general, which can be applied to load other metals such as Au and Pt on monolayer HNb₃O₈ NS. It is anticipated that this work can extend the facile preparation of noble metal/nanosheet 2D heterostructures, as well as promote the simultaneous capture of duple renewable thermal and photon energy sources to drive an energy efficient catalytic process.

Engineering a highly dispersed co-catalyst on a few-layered catalyst for efficient photocatalytic H2 evolution: a case study of Ni(OH)2/HNb3O8 nanocomposites

Ni(OH)₂ has been highly dispersed on HNb₃O₈ nanosheets and the composites exhibited greatly enhanced photocatalytic activity.