Electron transfer in heterojunction catalysts

Heterojunction catalysis, the cornerstone of the modern chemical industry, shows potential to tackle the growing energy and environmental crises. Electron transfer (ET) is ubiquitous in heterojunction catalysts, and it holds great promise for improving the catalytic efficiency by tuning the electronic structures or building internal electric fields at interfaces. This perspective summarizes the recent progress of catalysis involving ET in heterojunction catalysts and pinpoints its crucial role in catalytic mechanisms. We specifically highlight the occurrence, driving forces, and applications of ET in heterojunction catalysis. For corroborating the ET processes, common techniques with measurement principles are introduced. We end with the limitations of the current study on ET, and envision future challenges in this field.

Electronic and optical properties of a novel two-dimensional semiconductor material TlPt2S3: a first-principles study

Two-dimensional (2D) materials have attracted widespread attention due to their unique physical and chemical properties. Here, by using density functional theory calculations, we suggest a novel 2D TlPt₂S₃ material whose layered bulk counterpart was synthesized in 1973. Theoretical calculation results indicate that the exfoliating energy of monolayer and bilayer TlPt₂S₃ is 34.96 meV Å^-2 and 36.03 meV Å^-2. We systematically studied the electronic and optical properties of monolayer and bilayer TlPt₂S₃, and revealed that they are indirect band gap semiconductors with band gaps of 2.26 eV and 2.10 eV, respectively. Monolayer and bilayer TlPt₂S₃ exhibit superior carrier mobility (901.63 cm² V^-1 s^-1 and 13635.04 cm² V^-1 s^-1 for electron mobility of the monolayer and bilayer, respectively) and photocatalytic performance (as high as 1 × 10⁵ light absorption coefficient in the visible light region). Interestingly, we find that monolayer TlPt₂S₃ has significant hydrogen evolution performance, while in the bilayer, the electron band distribution shows complete oxygen evolution ability, which indicates that the proposed monolayer and bilayer TlPt₂S₃ are potential novel 2D materials suitable for photocatalytic water splitting driven by visible light.

Boosting the photocatalytic H2 evolution activity of type-II g-GaN/Sc2CO2 van der Waals heterostructure using applied biaxial strain and external electric field

Two-dimensional (2D) van der Waals (vdW) heterostructures are a new class of materials with highly tunable bandgap transition type, bandgap energy and band alignment. Herein, we have designed a novel 2D g-GaN/Sc2CO2 heterostructure as a potential solar-driven photocatalyst for the water splitting process and investigate its catalytic stability, interfacial interactions, and optical and electronic properties, as well as the effects of applying an electric field and biaxial strain using first-principles calculation. The calculated lattice mismatch and binding energy showed that g-GaN and Sc2CO2 are in contact and may form a stable vdW heterostructure. Ab initio molecular dynamics and phonon dispersion simulations show thermal and dynamic stability. g-GaN/Sc2CO2 has an indirect bandgap energy with appropriate type-II band alignment relative to the water redox potentials. Meanwhile, the interfacial charge transfer from g-GaN to Sc2CO2 can effectively separate electron-hole pairs. Moreover, a potential drop of 3.78 eV is observed across the interface, inducing a built-in electric field pointing from g-GaN to Sc2CO2. The heterostructure shows improved visible-light optical absorption compared to the isolated g-GaN and Sc2CO2 monolayers. Our study demonstrates that tunable electronic and structural properties can be realised in the g-GaN/Sc2CO2 heterostructure by varying the electric field and biaxial strain. In particular, the compressive strain and negative electric field are more effective for promoting hydrogen production performance. Since it is challenging to tune the electric field and biaxial strain experimentally, our research provides strategies to boost the performance of MXene-based heterojunction photocatalysts in solar harvesting and optoelectronic devices.

Investigation of the mechanism of overall water splitting in UV-visible and infrared regions with SnC/arsenene vdW heterostructures in different configurations

Monolayer arsenene presents good stability and high photogenic carrier mobility. However, a high photogenic electron and hole pair recombination rate seriously reduces its photocatalytic activity. The photocatalytic activity can be effectively improved by building type II heterostructures. In this work, SnC/arsenene heterostructures in three configurations are studied using first-principles calculations. Their structure, stability, and electronic and photocatalytic properties are investigated. It is found that all SnC/arsenene heterostructures are stable, and form type-II band edges, which effectively promote the transfer of photogenerated electrons from the SnC monolayer to the arsenene sheet. The charge transfer between SnC and arsenene leads to a built-in electric field in the interface region, which is favorable for inhibiting photogenic electron and hole pair recombination. Compared with the monolayer arsenene, the photocatalytic activity is greatly improved and the absorption spectrum of SnC/arsenene heterostructures is expanded. Attractively, these three heterostructures present two different photocatalytic mechanisms. H1 and H3 configurations were taken as examples to study their photocatalytic properties for overall water splitting at varying pH values and external strains. We found that alkaline conditions were more favorable for photocatalysis of SnC/arsenene heterostructures. In particular, H3 can still achieve full photocatalytic water decomposition in the near infrared region. These results show that the SnC/arsenene heterostructures are a prospective material for photocatalysis application.

Computational insights into structural, electronic and optical characteristics of GeC/C2N van der Waals heterostructures: effects of strain engineering and electric field

Vertical heterostructures from two or more than two two-dimensional materials are recently considered as an effective tool for tuning the electronic properties of materials and for designing future high-performance nanodevices. Here, using first principles calculations, we propose a GeC/C2N van der Waals heterostructure and investigate its electronic and optical properties. We demonstrate that the intrinsic electronic properties of both GeC and C2N monolayers are quite preserved in GeC/C2N HTS owing to the weak forces. At the equilibrium configuration, GeC/C2N HTS forms the type-II band alignment with an indirect band gap of 0.42 eV, which can be considered to improve the effective separation of electrons and holes. Besides, GeC/C2N vdW-HTS exhibits strong absorption in both visible and near ultra-violet regions with an intensity of 105 cm-1. The electronic properties of GeC/C2N HTS can be tuned by applying an electric field and vertical strains. The semiconductor to metal transition can be achieved in GeC/C2N HTS in the case when the positive electric field of +0.3 V Å-1 or the tensile vertical strain of -0.9 Å is applied. These findings demonstrate that GeC/C2N HTS can be used to design future high-performance multifunctional devices.

Study of the GaAs/SiH van der Waals type-II heterostructure: a high efficiency photocatalyst promoted by a built-in electric field

The built-in electric field promotes GaAs/SiH as a high efficiency photocatalyst for water splitting in visible light.

Effects of different surface functionalization on the electronic properties and contact types of graphene/functionalized-GeC van der Waals heterostructures

Constructing vertical heterostructures by placing graphene (Gr) on two-dimensional materials has recently emerged as an effective way to enhance the performance of nanoelectronic and optoelectronic devices.

PtSe2/SiH van der Waals type-II heterostructure: a high efficiency photocatalyst for water splitting

PtSe₂/SiH type-II van der Waals heterostructure is a highly efficient photocatalyst for water splitting in visible light.

Band alignment and optical features in Janus-MoSeTe/X(OH)2 (X = Ca, Mg) van der Waals heterostructures

van der Waals heterostructures can be effectively used to enhance the electronic and optical properties and extend the application range of two-dimensional materials.