Atomic-Level Regulated 2D ReSe2 : A Universal Platform Boostin Photocatalysis

In Situ Atomic Tracking on the Interfacial Etching and Reconfiguration of Cu-ReSe2 Contact during Thermal Annealing

The Schottky barrier height can be greatly affected by the metal diffusion, reaction, and covalent bonding formation at the contact. Exploring novel methods and revealing the fundamental mechanisms for contact engineering are of vital importance for microelectronic devices. Here, the annealing induced interfacial reactions at Cu-ReSe2 contact are dynamically revealed from the atomic scale. Accompanied by the diffusion of Se to Cu, ReSe2 is gradually decomposed to a thin Re interlayer through a "chain-by-chain" manner. Theoretical calculations show that the Cu atoms can facilitate the chemical bond breaking of ReSe2, significantly lowering the Se diffusion energy barrier toward Cu. The formed Re/ReSe2 heterostructure presents a metal-like band structure, which underscores the critical role of Cu in altering the interfacial chemistry and promoting carrier transport across the interface. Our results can provide vital insights into the contact properties of ReSe2 and provide a possible method for fabricating high-performance ReSe2-based devices.

(ReMoV)X2 (X = S, Se) Ternary Alloy Nanosheets for Enhanced Electrocatalytic Hydrogen Evolution Reaction

Modulating the electronic structure of 2D transition metal dichalcogenides via alloying can extend their potential applications. In this study, composition-tuned ternary alloy nanosheets of (ReMoV)X2 (X = S and Se) are synthesized using solvothermal and colloidal reactions, respectively. Ternary alloying occurred with homogeneous atomic mixing over a wide range of compositions (xV = 0.16-0.80). Compared to (ReV)X2 binary alloying, ternary alloying produces a more metallic phase with less oxidation. Increasing xV induces a phase change into a more metallic 1T phase. The (ReMoV)S2 nanosheets demonstrate enhanced electrocatalytic activity toward the acidic hydrogen evolution reaction (HER) compared to (ReV)S2. Density functional theory calculations predict that ternary alloying increases the metallicity of the nanosheets. In addition, the Gibbs free energy calculation for hydrogen adsorption (ΔGH*) shows that ternary alloying effectively activates the basal S atoms for the HER, supporting the enhanced catalytic performance observed experimentally.

Modulation of Charge-Ordered Carriers Within 3D Fe3S4 Polyurethane Foam (Fe3S4-PUF) for Efficient Iron Redox Cycling and Continuous-Flow Photocatalytic Antibiotics Degradation

Photocatalytic antibiotic degradation is an energy-efficient and environmentally friendly approach with the potential for large-scale application but is severely constrained by the lack of efficient and stable catalysts to produce reactive oxygen species (ROS). This research introduces a charge-ordered 3D Fe3S4-PUF composite integrated into a custom-built photocatalytic tandem continuous-flow cylinder reactor (TCCR) for antibiotic degradation. The system consistently achieves 100% tetracycline (TC) degradation efficiency with Fe3S4-PUF during 130 h of continuous operation, benefiting from the charge-ordered 3D Fe3S4-PUF framework and the TCCR design. Mechanism investigations reveal that the abundant Lewis basic ≡SH site and light-induced sustainable Fe2+/Fe3+ redox cycling within Fe3S4 facilitates the production of H2O2 and ROS. Density functional theory (DFT) calculations indicate that Fe2+ acts as an active site for capturing and activating O2, leading to either one-electron (O2→O2 •-→H2O2→•OH) or two-electron transfer (O2→H2O2) pathways. Meanwhile, photogenerated electron and the oxygen atoms in H2O2 provide electrons to Fe3+, facilitating the reduction of Fe3+ to Fe2+, thus elucidating the Fe2+/Fe3+ redox cycling mechanism. Moreover, the 3D PUF structure enhances the mass transfer and pollutant-ROS interactions. The continuous-flow photocatalytic reaction validate the efficient antibiotic degradation of Fe3S4-PUF composite, suggesting its potential for implementation in large-scale antibiotic wastewater treatment systems.

Optimizing Interfacial Charge Dynamics and Quantum Effects in Heterodimensional Superlattices for Efficient Hydrogen Production

Superlattice materials have emerged as promising candidates for water electrocatalysis due to their tunable crystal structures, electronic properties, and potential for interface engineering. However, the catalytic activity of transition metal-based superlattice materials for the hydrogen evolution reaction (HER) is often constrained by their intrinsic electronic band structures, which can limit charge carrier mobility and active site availability. Herein, a highly efficient electrocatalyst based on a VS2-VS heterodimensional (2D-1D) superlattice with sulfur vacancies is designed addressing the limitations posed by the intrinsic electronic structure. The enhanced catalytic performance of the VS2-VS superlattice is primarily attributed to the engineered heterojunction, where the work function difference between the VS2 layer and VS chain induces a charge separation field that promotes efficient electron-hole separation. Introducing sulfur vacancies further amplifies this effect by inducing quantum localization of the separated electrons, thereby significantly boosting HER activity. Both theoretical and experimental results demonstrate that the superlattice achieves a ΔGH* of -0.06 eV and an impressively low overpotential of 46 mV at 10 mA·cm-2 in acidic media, surpassing the performance of commercial Pt/C while maintaining exceptional stability over 15 000 cycles. This work underscores the pivotal role of advanced material engineering in designing catalysts for sustainable energy applications.

A Strongly Coupled 1T'-ReSe2@2H-MoSe2 van der Waals Heterostructure for Efficient Electrocatalytic Hydrogen Evolution at High Current Densities

Developing efficient and durable non-noble metal electrocatalysts for high current-density hydrogen evolution reactions (HER) is a pressing requirement for commercial industrial electrolyzers. In this study, a vertical 1T'-ReSe2@2H-MoSe2 van der Waals heterostructure was developed through interface engineering to enhance the advantages of each component and expose numerous active sites. Experimental investigations and density functional theory calculations demonstrate significant electronic coupling at the interface between 1T'-ReSe2 and 2H-MoSe2, with suitable Gibbs free energy for hydrogen adsorption. The 1T'-ReSe2@2H-MoSe2 heterostructure catalyst achieves high current density HER with low overpotentials of 191 mV to generate up to 800 mA/cm2 in 0.5 M H2SO4, outperforming commercial 5 % Pt/C catalysts. Moreover, this catalyst exhibits rapid reaction kinetics and long-term durability, illustrating a successful approach to designing efficient heterostructure electrocatalysts for hydrogen production through interface engineering.

Defect-Induced Atomical Zn-O/N-C Bonding Promotes Efficient Charge Transfer in S-Scheme Interface for Bubble Level Solar Hydrogen Production

Establishing efficient and clear atomic-level charge transfer channels presents a significant challenge in the design of effective photocatalysts. A sound strategy has been developed herein involving the construction of defect-induced heterostructures that create chemical bonds serving as charge transfer channels at the heterojunction interface. In situ XPS, alongside theoretical calculations, demonstrates the successful construction of Zn-O/N-C as atomic charge transfer channels. Our findings reveal that the introduction of zinc vacancies (VZn) reduces the carrier transport activation energy (CTAE) from 155.2 meV for ZIS/CN to 128.7 meV for VZn-ZIS/CN. Consequently, the optimal VZn-ZIS/CN achieves a high hydrogen evolution rate of 22.26 mmol g-1 h-1 without Pt as a cocatalyst, which is approximately 57 times greater compared to that of ZIS/CN. Notably, hydrogen is generated at bubble levels under natural sunlight. This work provides insights into the mechanisms by which defect-induced heterostructure building strategies can introduce chemical bonds at the heterojunction interface.

Single atoms meeting 2D materials: an excellent configuration for photocatalysis

Photocatalysis has problems such as low light absorption efficiency and rapid recombination of photogenerated electron-hole pairs. Many studies have been conducted to improve these issues. This review encapsulates the progress and applications of two pioneering research fields in catalysis: single-atom and two-dimensional (2D) material catalysts. The advent of this new type of catalysts, which integrates single atoms onto 2D materials, has seen remarkable growth in recent years, offering distinctive advantages. The article delves into the array of synthesis methods employed for loading single atoms onto 2D materials, including the wet chemical approach, atomic layer deposition technique, and thermal decomposition method. A highlight of the review is the superior attributes of single-atom catalysts supported on 2D materials (SACs-2D) in photocatalysis, such as extending the light absorption wavelength range, enhancing the efficiency of photogenerated electron-hole pair separation, and accelerating redox kinetics. The review meticulously examines the diverse applications of SACs-2D photocatalysis, which encompass water splitting for hydrogen generation, carbon dioxide reduction, degradation of organic pollutants, nitrogen fixation and hydrogen peroxide synthesis. These applications demonstrate the potential of SACs-2D materials in addressing pressing environmental and energy challenges. Finally, this article evaluates the current state of this burgeoning field, discussing the opportunities and challenges ahead.

Modulating built-in electric field via Bi-VO4-Fe interfacial bridges to enhance charge separation for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting on semiconductor electrodes is considered to be one of the important ways to produce clean and sustainable hydrogen fuel, which is a great help in solving energy and environmental problems. Bismuth vanadate (BiVO4) as a promising photoanode for photoelectrochemical water splitting still suffers from poor charge separation efficiency and photo-induced self-corrosion. Herein, we develop heterojunction-rich photoanodes composed of BiVO4 and iron vanadate (FeVO4), coated with nickel iron oxide (NiFeOx/FeVO4/BiVO4). The formation of the interface between BiVO4 and FeVO4 (Bi-VO4-Fe bridges) enhances the interfacial interaction, resulting in improved performance. Meanwhile, high-conductivity FeVO4 and NiFeOx oxygen evolution co-catalysts effectively enhance bulk electron/hole separation, interface water's kinetics and photostability. Concurrently, the optimized NiFeOx/FeVO4/BiVO4 possesses a remarkable photocurrent density of 5.59 mA/cm2 at 1.23 V versus reversible hydrogen electrode (vs RHE) under AM 1.5G (Air Mass 1.5 Global) simulated sunlight, accompanied by superior stability without any decreased of its photocurrent density after 14 h. This work not only reveals the crucial role of built-in electric field in BiVO4-based photoanode during PEC water splitting, but also provides a new guide to the design of efficient photoanode for PEC.

Solar light driven atomic and electronic transformations in a plasmonic Ni@NiO/NiCO3 photocatalyst revealed by ambient pressure X-ray photoelectron spectroscopy

This work employs ambient pressure X-ray photoelectron spectroscopy (APXPS) to delve into the atomic and electronic transformations of a core-shell Ni@NiO/NiCO3 photocatalyst - a model system for visible light active plasmonic photocatalysts used in water splitting for hydrogen production. This catalyst exhibits reversible structural and electronic changes in response to water vapor and solar simulator light. In this study, APXPS spectra were obtained under a 1 millibar water vapor pressure, employing a solar simulator with an AM 1.5 filter to measure spectral data under visible light illumination. The in situ APXPS spectra indicate that the metallic Ni core absorbs the light, exciting plasmons, and creates hot electrons that are subsequently utilized through hot electron injection in the hydrogen evolution reaction (HER) by NiCO3. Additionally, the data show that NiO undergoes reversible oxidation to NiOOH in the presence of water vapor and light. The present work also investigates the contribution of carbonate and its involvement in the photocatalytic reaction mechanism, shedding light on this seldom-explored aspect of photocatalysis. The APXPS results highlight the photochemical reduction of carbonates into -COOH, contributing to the deactivation of the photocatalyst. This work demonstrates the APXPS efficacy in examining photochemical reactions, charge transfer dynamics and intermediates in potential photocatalysts under near realistic conditions.

Heteroatom-Doped Ag25 Nanoclusters Encapsulated in Metal-Organic Frameworks for Photocatalytic Hydrogen Production

Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light-induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg24 (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal-organic framework (MOF), UiO-66-NH2, affording MAg24@UiO-66-NH2. Strikingly, compared with Ag25@UiO-66-NH2, the MAg24@UiO-66-NH2 doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg24@UiO-66-NH2 presents the best activity up to 3.6 mmol g-1 h-1, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X-ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg24 NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z-scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production.

Schottky junction enhanced H2 evolution for graphitic carbon nitride-NiS composite photocatalysts

As one of the most promising photocatalysts for H2 evolution, graphitic carbon nitride (CN) has many appealing attributes. However, the activity of pristine CN remains unsatisfactory due to severe charge carrier recombination and lack of active sites. In this study, we report a two-step approach for the synthesis of CN nanotubes (TCN) loaded with NiS nanoparticles. The resulting composite photocatalysts gave a H2 evolution rate of 752.9 μmol g-1 h-1, which is 42.3 times higher compared to the pristine CN photocatalyst. Experimental and simulation results showed that the Schottky junction which was formed between TCN and NiS was key to achieving high activity. This is because the formation of Schottky junction prevented the backflow of electrons from NiS to TCN, which improved charge separation efficiency. More importantly, it also led to the accumulation of electrons on NiS, which significantly weakened the SH bond, such that the intermediate hydrogen species desorbed more easily from NiS surface to promote H2 evolution activity.

Recent advancement on photocatalytic plastic upcycling

More than 8 billion tons of plastics have been generated since 1950. About 80% of these plastics have been dumped in landfills or went into natural environments, resulting in ever-worsening contamination. Among various strategies for waste plastics processing (e.g., incineration, mechanical recycling, thermochemical conversion and electrocatalytic/photocatalytic techniques), photocatalysis stands out as a cost-effective, environmentally benign and clean technique to upcycle plastic waste at ambient temperature and pressure using solar light. The mild reaction conditions for photocatalysis enable the highly selective conversion of plastic waste into targeted value-added chemicals/fuels. Here, we for the first time summarize the recent development of photocatalytic plastic upcycling based on the chemical composition of photocatalysts (e.g., metal oxides, metal sulfides, non-metals and composites). The pros and cons of various photocatalysts have been critically discussed and summarized. At last, the future challenges and opportunities in this area are presented in this review.

Free-Electron Inversive Modulation to Charge Antibonding Orbital of ReS2 Cocatalyst for Efficient Photocatalytic Hydrogen Generation

The free electron transfer between cocatalyst and photocatalyst has a great effect on the bonding strength between the active site and adsorbed hydrogen atom (Hads ), but there is still a lack of effective means to purposely manipulate the electron transfer in a beneficial direction of H adsorption/desorption activity. Herein, when ReSx cocatalyst is loaded on TiO2 surface, a spontaneous free-electron transfer from ReSx to TiO2 happens due to the smaller work function of ReSx , causing an over-strong S-Hads bond. To prevent the over-strong S-Hads bonds of ReSx in the ReSx /TiO2 , a free-electron reversal transfer strategy is developed to weaken the strong S-Hads bonds via increasing the work function of ReSx by incorporating O to produce ReOSx cocatalyst. Research results attest that a larger work function of ReOSx than that of TiO2 can induce reversal transfer of electrons from TiO2 to ReOSx to produce electron-rich S(2+δ)- , causing the increased antibonding-orbital occupancy of S-Hads in ReOSx /TiO2 . Accordingly, the stability of adsorbed H on S sites is availably decreased, thus weakening the S-Hads of ReOSx . In this case, an electron-rich S(2+δ)- -mediated "capture-hybridization-conversion" mechanism is raised . Benefiting from such property, the resultant ReOSx /TiO2 photocatalyst exhibits a superior H2 -evolution rate of 7168 µmol h-1 g-1 .

Anisotropic Phonon Behavior and Phase Transition in Monolayer ReSe2 Discovered by High Pressure Raman Scattering

Re-based transition metal dichalcogenides have attracted extensive attention owing to their anisotropic structure and excellent properties in applications such as optoelectronic devices and electrocatalysis. The present study methodically investigated the evolution of specific Raman phonon mode behaviors and phase transitions in monolayer and bulk ReSe2 under high pressure. Considering the distinctive anisotropic characteristics and the vibration vectors of Re and Se atoms exhibited by monolayer ReSe2, we perform phonon dispersion calculations and propose a methodology utilizing pressure-dependent polarized Raman measurements to explore the precise structural evolution of monolayer ReSe2 under the stress fields. Varied behaviors of the Eg-like and Ag-like modes, along with their specific vector transformations, have been identified in the pressure range 0-14.59 GPa. The present study aims to offer original perspectives on the physical evolution of Re-based transition metal dichalcogenides, elucidating their fundamental anisotropic properties and exploring potential applicability in diverse devices.

Photocatalytic Applications of ReS2-Based Heterostructures

ReS2-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReS2 with other wide band-gap semiconductors, have shown promising performance in energy conversion and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReS2-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of CO2, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReS2-based heterostructures for photocatalysis.