Two-dimensional blue-phase CX (X = S, Se) monolayers with high carrier mobility and tunable photocatalytic water splitting capability

Ferroelectric polarization promotes a CdS/In2Se3 heterostructure for photocatalytic water splitting

The rapid recombination of photogenerated electrons and holes greatly limits the efficiency of photocatalyst based on semiconductor. In order to address this issue, we predicted a novel ferroelectric polarized heterojunction photocatalyst, CdS/In2Se3, which enables the spontaneous overall water splitting reaction. The CdS/In2Se3 heterojunction exhibits a band-edge staggered alignment and it is easy to form a direct Z-scheme charge transfer pathway. Besides, the built-in electric field (Eint) in the CdS/In2Se3 heterojunction promoted the charge transfer of CdS/In2Se3, leading to an improved separating efficiency of photo-generated carriers. Moreover, the vertical intrinsic polarized electric field (Ep) not only alters the position of the band edge but also reduces the bandgap limitations commonly associated with photocatalytic materials. Furthermore, the CdS/In2Se3 heterojunctions demonstrate separate catalytic activity for the hydrogen evolution reaction (HER) on the surface of the CdS monolayer and oxygen evolution reaction (OER) on the surface of In2Se3, respectively. Notably, the CdS/In2Se3-down configuration enables spontaneous photocatalytic water splitting in pH = 7, while the CdS/In2Se3-up configuration efficiently facilitates the HER process. This study highlights the significant advantages of CdS/In2Se3 heterojunctions as photocatalytic materials, offering unique insights into the development and research of this promising heterojunction architecture.

Can P3S and C3S monolayers be used as anode materials in metal-ion batteries? An answer from first-principles study

With the urgent need for efficient energy storage devices, significant attention has been directed to researching and developing promising anode materials for metal-ion batteries. Through density functional study, we successfully predicted the electrochemical performance of P3S and C3S monolayers for the first time, which could be used in alkali metal (Li, Na, and K)-ion batteries. Our study examines the energetic, dynamic, and thermal stabilities of pristine monolayers. The electronic structures of the pristine nanosheets are wide-gap semiconductors. After single metalation on the monolayers, the composite systems become metallic. Charge-density difference (CDD) analysis indicates that charge transfer occurs from alkali metal atoms to the P3S and C3S monolayers, and Bader charge analysis quantifies the amount of charge transfer. We analyzed how readily a single adatom diffuses within the 2D structures. One example is the diffusion of K on C3S, which has a low barrier value of 0.06 eV and seems practically barrierless. Our predicted composite systems report considerable theoretical storage capacity (C); for example, hexalayer K-adsorbed C3S shows a storage capacity of 1182.79 mA h g-1. The estimated open-circuit voltage (OCV) values suggest that the C3S monolayer is a promising anode material for Li-, Na-, and K-ion batteries, whereas the P3S monolayer is suitable as a cathode material for Li-, Na-, and K-ion batteries.

Photo-Induced C1 Substitution Using Methanol as a C1 Source

The development of sustainable and efficient C1 substitution methods is of central interest for organic synthesis and pharmaceuticals production, the methylation motifs bound to a carbon, nitrogen, or oxygen atom widely exist in natural products and top-selling drugs. In the past decades, a number of methods involving green and inexpensive methanol have already been disclosed to replace industrial hazardous and waste-generating C1 source. Among the various efforts, photochemical strategy is considered as a "renewable" alternative that shows great potential to selectively activate methanol to achieve a series of C1 substitutions at mild conditions, typically C/N-methylation, methoxylation, hydroxymethylation, and formylation. Herein the recent advances in selective transformation of methanol to various C1 functional groups via well-designed photochemical systems involving different types of catalysts or not is systematically reviewed. Both the mechanism and corresponding photocatalytic system were discussed and classified on specific methanol activation models. Finally, the major challenges and perspectives are proposed.

Enhanced Photocatalytic Activity of Two-Dimensional Polar Monolayer SiTe for Water-Splitting via Strain Engineering

A two-dimensional (2D) polar monolayer with a polarization electric field can be used as a potential photocatalyst. In this work, first principle calculations were used to investigate the stability and photocatalytic properties of 2D polar monolayer SiTe as a potential promising catalyst in water-splitting. Our results show that the 2D polar monolayer SiTe possesses an indirect band gap of 2.41 eV, a polarization electric field from the (001) surface to the (001¯) surface, a wide absorption region, and a suitable band alignment for photocatalytic water-splitting. We also discovered that the photocatalytic activity of 2D polar monolayer SiTe could be effectively tuned through strain engineering. Additionally, strain engineering, particularly compressive strain in the range from −1% to −3%, can enhance the photocatalytic activity of 2D polar monolayer SiTe. Overall, our findings suggest that 2D polar monolayer SiTe has the potential to be a promising catalyst for photocatalytic water-splitting using visible light.

One Stone Two Birds: Utilization of Solar Light for Simultaneous Selective Phenylcarbinol Oxidation and H2 Production over 0D/2D-3D Pt/In2S3 Schottky Junction

Precise regulation and control solar-light-driven charges photoexcited on photocatalysts for separation-transfer and target redox reactions is an attractive and challenging pathway toward sustainability. Herein, 0D/2D-3D Pt/In2S3 Schottky junction was fabricated for simultaneous selective phenylcarbinol conversion into value-added aldehydes and production of clean energy H2 by directly utilizing photoexcited holes and electrons in one reaction system under mild reaction conditions. In contrast to pure water splitting and pure In2S3, the reaction thermodynamics and kinetics of H2 evolution on the Pt/In2S3 were significantly enhanced. The optimized 0.3% Pt/In2S3 exhibited the highest and most stable photocatalytic activity with 22.1 mmol g−1 h−1 of H2 production rate and almost 100% selectivity of benzaldehyde production. Notably, this dual-function photocatalysis also exhibited superiority in contrast to sacrificial-agent H2 evolution reactions such as lactic acid, Na2S, methanol and triethanolamine. The turnover frequency (TOF) could reach up to ~2394 h−1. The Pt clusters anchored at the electron location and strong metal-support interactions (SMSI) between Pt and In2S3 synergistically improved the spatial charge separation and directional transportation (~90.1% of the charge transport efficiency could be achieved over the Pt/In2S3 hybrid), and thus result in significant enhancement of photocatalytic H2 evolution with simultaneous benzaldehyde production.

A semiconductor Sc2S3 monolayer with ultrahigh carrier mobility for UV blocking filter application

For humans, ultraviolet (UV) light from sun is harmful to our eyes and eye-related cells. This detrimental fact requires scientists to search for a material that can efficiently absorb UV light while allowing lossless transmission of visible light. Using an unbiased first-principles swarm intelligence structure search, we explored two-dimensional (2D) Sc-S crystals and identified a novel Sc₂S₃ monolayer with good thermal and dynamical stability. The optoelectronic property simulations revealed that the Sc₂S₃ monolayer has a wide indirect bandgap (3.05 eV) and possesses an ultrahigh carrier mobility (2.8 × 10³ cm² V^-1 s^-1). Remarkably, it has almost transparent visible light absorption, while it exhibits an ultrahigh absorption coefficient up to × 10⁵ cm^-1 in the ultraviolet region. Via the application of biaxial strain and thickness modulation, the UV light absorption coefficients of Sc₂S₃ can be further improved. These findings manifest an attractive UV blocking optoelectronic characteristic of the Sc₂S₃ configuration as a prototypical nanomaterial for the potential application in UV blocking filters.

Conductive C3NS Monolayer with Superior Properties for K Ion Batteries

K-ion batteries (KIBs) have been considered as appealing alternatives to Li ion batteries due to the high abundance of K, their high working voltages, and allowing the use of mature LIB technology. Thus far, anode materials that can meet the rigorous requirements of KIBs are still rather rare. Here, we have identified a desirable anode material, a metallic C₃NS monolayer with high stability, a high storage capacity of 980 mAh/g, a low diffusion barrier of 0.24 eV, and a low open-circuit voltage of 0.36 V, through first-principles calculations. Metallic C₃NSK_n (n = 1-3) can ensure a high electron conductivity during the charge/discharge process. Valence electrons of the N atom in a triangular bipyramid configuration favor the formation of a planar edge-sharing hexagonal C₄N₂ unit and delocalized π bonding with C 2p electrons. The lone pair electrons of the S atom induce strong interactions with K atoms, facilitating storage capacity. These interesting properties make the C₃NS monolayer a promising anode for KIBs.

NiO nanobelts with exposed {110} crystal planes as an efficient electrocatalyst for the oxygen evolution reaction

The electrocatalytic oxygen evolution reaction (OER) is necessary and challenging for converting renewable electricity into clean fuels, because of its complex proton coupled multielectron transfer process. Herein, we investigated the crystal plane effects of NiO on the electrocatalytic OER activity through combining experimental studies and theoretical calculations. The experimental results reveal that NiO nanobelts with exposed {110} crystal planes show much higher OER activity than NiO nanoplates with exposed {111} planes. The efficient OER activity of the {110} crystal planes comes from their intrinsically high catalytic ability and fast charge transfer kinetics. Density functional theory (DFT) shows that the {110} crystal planes possess a lower theoretical overpotential value for the OER, leading to a high electrocatalytic performance. This research broadens our vision to design efficient OER electrocatalysts by the selective exposure of specific crystal planes.

Hybrid density functional study on band structure engineering of ZnS(110) surface by anion–cation codoping for overall water splitting

The (Ru + C)-codoped ZnS(110) surface is predicted to be a potential candidate for solar-driven water splitting.

First-principles investigation of potential water-splitting photocatalysts and photovoltaic materials based on Janus transition-metal dichalcogenide/WSe2 heterostructures

In order to evaluate their potential for use in photocatalytic water splitting and photovoltaic solar cells, WSe2/JTMDC heterostructures with various stacking patterns are built. For the intended uses, the materials show promise.

Two-Dimensional TeB Structures with Anisotropic Carrier Mobility and Tunable Bandgap

Two-dimensional (2D) semiconductors with desirable bandgaps and high carrier mobility have great potential in electronic and optoelectronic applications. In this work, we proposed α-TeB and β-TeB monolayers using density functional theory (DFT) combined with the particle swarm-intelligent global structure search method. The high dynamical and thermal stabilities of two TeB structures indicate high feasibility for experimental synthesis. The electronic structure calculations show that the two structures are indirect bandgap semiconductors with bandgaps of 2.3 and 2.1 eV, respectively. The hole mobility of the β-TeB sheet is up to 6.90 × 10² cm² V^-1 s^-1. By reconstructing the two structures, we identified two new horizontal and lateral heterostructures, and the lateral heterostructure presents a direct band gap, indicating more probable applications could be further explored for TeB sheets.

Anisotropic and High-Mobility C3S Monolayer as a Photocatalyst for Water Splitting

Taking into account the high conductivity and stability of carbon materials, such as graphene, and the strong polar covalent bonding character of main-group compounds, we explore potential 2D materials in the C-S binary system through first-principles structure search calculations. Herein, a hitherto unknown semiconducting C₃S monolayer is identified, consisting of well-known n-biphenyl and S atom linked benzenes, exhibiting an obvious direction-dependent atomic arrangement. Thus, it exhibits anisotropic mechanical properties and carrier mobility. Its electron mobility reaches 2.14 × 10⁴ cm² V^-1 s^-1 in the b direction, along which n-biphenyl units are arranged, and is much higher than that in the well-used MoS₂ monolayer and black phosphorus. Meanwhile, the C₃S monolayer has high optical absorption coefficients (10⁵ cm^-1), high thermal and dynamical stabilities, and a moderate ability to split water. All these desirable properties make the C₃S monolayer a promising candidate for applications in novel optoelectronic devices.