We propose a novel excellent two-dimensional photocatalyst SnN3 monolayer using first-principles calculations. The stability of SnN3 monolayer have been examined via formation energy, phonon spectrum and ab initio molecular dynamics calculations. Large optical absorption capacity plays significant role in the enhancement of photocatalytic splitting of water. The SnN3 monolayer have ultra-high optical absorption capacity in visible region, which is as three and four times as that of SnP3 and MoS2 monolayer, respectively. Available potential and appropriate band positions indicating the ability of overall water splitting even in a wide strain range. Electronic properties of SnN3 monolayer can also be engineered effectively via the external strain, such as the conversion from in-direct band gap to direct band gap. The applied electric field splits the energy levels due to Stark effect, resulting in states accumulation and smaller gap width
Using an organometallic precursor, TiO$_2$ coatings were fabricated on surfaces of quartz, zircon and rutile sands. X ray Diffraction, X ray Fluorescence, UV Vis spectroscopy and surface area measurement were used to characterise support materials. The phase composition and morphology of the coatings were characterised by laser Raman spectroscopy and SEM respectively. A packed bed reactor was used to study the inactivation of Escherichia coli in recirculating water by the supported photocatalysts. It was found that the sand grains were well coated with a homogenous layer of TiO2 and coatings w…
Investigation of a high-entropy oxide photocatalyst for hydrogen generation by first-principles calculations coupled with experiments: Significance of electronegativity
Perovskite SrTiO3 (STO) is an attractive photocatalyst for solar water splitting, but suffers from a limited photoresponse in the ultraviolet spectral range due to its wide band gap. By means of hybrid density functional theory calculations, we systematically study engineering its band gap via doping 4d and 5d transition metals M (M=Zr, Nb, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir and Pt) and chalcogen elements Y (Y=S and Se). We find that transition metal dopant M either has no effect on STO band gap or introduces detrimental mid-gap states, except for Pd and Pt that are able to reduce the S…
Visible-light photocatalyst titanium dioxide (TiO2) was successfully prepared via a novel and facile single-mode microwave assisted synthesis process. In this one-step synthesis, Ti as target material selectively oxides in magnetic field throughout rapid heating, whose process requires less energy consumption and short time. In obtained TiO2, self-doping of Ti3+ was confirmed, which makes TiO2 performed sufficient light absorption in visible region with wavelength above 400 nm. Such Ti3+ self-doped TiO2 exhibits much narrower optical bandgap (2.14 eV) to compare with stoichiometric TiO2 (3.0-3…
We study the surface stability of the layered bismuth-oxide Bi$_2$WO$_6$ and Bi$_2$MoO$_6$ photocatalysts, which belong to the series of Aurivillius (Bi$_2$A$_{n-1}$B$_{n}$O$_{3n+3}$) perovskites and have been proposed as efficient visible-light absorbers, due to favorable electronic hybridization induced by the Bi 6s and 6p orbitals. We present a Newton--Raphson optimization of the charge distribution at the semiconductor--solution interface using the self-consistent continuum solvation (SCCS) model to describe the influence of the aqueous environment. Our analysis provides a description of t…
Recently, hydrogen generation by water-splitting photocatalysts is attracting attention as a sustainable and clean energy resource. Photocatalytic hydrogen-generation systems are much simpler, cheaper, and easier to scale up than the coupled systems of electrolysis and solar cells, wind-power generation, etc. However, photocatalytic hydrogen generation is currently inefficient. This paper proposes the monolayer of boron phosphide as a stable highly-efficient water-splitting photocatalyst by high-precision density-functional theory calculations using a HSE06 functional with a solvent effect. Th…
In this work, using a hybrid density functional theory (DFT) based calculation, we propose a new two-dimensional (2D) B-C-N material, $g-B_{3}C_{2}N_{3}$, with the promising prospect of metal-free photocatalysis. A comprehensive investigation demonstrates that it is a near ultraviolet (UV) absorbing direct band gap (3.69 eV) semiconductor with robust dynamical and mechanical stability. Estimating the band positions with respect to water oxidation and hydrogen reduction potential levels, we observe that $g-B_{3}C_{2}N_{3}$ monolayer shows the possibility to be used for hydrogen fuel generation …
Bandgap engineering has attracted increasing interest in the field of semiconductive materials with specific electrical and optical characteristics for various applications, such as solar energy harvesting, energy-related applications, and photocatalysts. Here, we propose a novel and facile method to obtain a combination of type-II structure and Ohmic contact by the fabrication of WO3/Ti-WOx/TiHyOz homo/heterojunction on a WO3 photocatalyst using ball milling. The morphology and structural characterizations of the material are obtained using UV-vis, SEM/EDS, XRD, Raman spectroscopy, and XPS. I…
The quest for efficient and economically accessible cleaner methods to develop sustainable carbon-free energy sources induced a keen interest in the production of hydrogen fuel. This can be achieved via the water-splitting process exploiting solar energy but requiring the use of adequate photocatalysts. Covalent triazine-based frameworks (CTFs) are target photocatalysts for water-splitting. Both electronic and structural characteristics of CTFs, optical bandgaps and porosity, are directly relevant for water-splitting. These can be engineered through chemical design. Porosity can be beneficial …
Black TiO2 with/without noble metal has been proposed for visible photocatalyst, still leaving poor catalyst efficiency. Alternatively, phase-mixed TiO2 such as anatase and rutile has been commonly used for visible catalysts with the inevitable inclusion of noble metal. Here, we perform a noble metal-free visible photocatalyst blue TiO2 with type-II band-aligned ordered anatase/disordered rutile structure, via phase-selective reduction with alkali metals. The changed band alignment in this heterostructure was identified by absorption and ultraviolet photoemission spectroscopy, which was furthe…
Two dimensional (2D) semiconducting light absorbers, have recently considered as promising components to improve the efficiency in the photocatalytic hydrogen production via water splitting. In this work, by employing density functional theory computations, we introduced novel SiX2 (X = P, As) nanosheets in tetragonal (penta-) and orthorhombic (rec-) phases, as promising light absorber semiconductors for overall water splitting. The predicted nanomembranes exhibit good mechanical, dynamical and thermal stabilities. They also show small cleavage energies in the range of 0.31 J/m2 to 0.39 J/m2, …
Submicron core/shell Ti/TiOx photocatalyst is successfully synthesized via single-mode magnetic microwave (SMMW) assisted direct oxidation of planetary ball-milled TiH2. The thickness of TiOx shell including highly concentrated defects such as Ti3+ and/or oxygen vacancies is controllable in the range from 6 to over 18 nm by varying the treatment time in the SMMW assisted reaction. In addition to its quite narrow optical bandgap (1.34-2.69 eV) and efficient visible-light absorption capacity, the submicron Ti/TiOx particle exhibits superior photocatalytic performance towards H2 production from w…
In recent years, conjugated polymers such as graphitic Carbon Nitride (g-C3N4) attracts major attention to the researchers for the harnessing of renewable energy and environmental remediation through photocatalytic water splitting. Its moderate electronic band gap structure helps to absorb large spectrum of abundant solar radiation for the generation of hydrogen, a high density chemical energy source, by water splitting method. Its outstanding physicochemical stability makes it a reliable energy conversion material. Another key attribute to the researchers is the simple way of synthesizing pri…
Photocatalytic water splitting represents a very promising but at the same time very challenging contribution to a clean and renewable route to produce hydrogen fuel. Developing efficient and cost-effective photocatalysts for water splitting is a growing need. For this purpose, semiconductor photocatalysts have attracted much more attention due to their stability and low manufacturing cost. Here, we have systematically applied several state-of-the-art advanced first-principles-based methodologies, viz., hybrid density functional theory, many-body perturbation theory (G$_0$W$_0$) and density fu…
Environmental contamination and human exposure to dyes have dramatically increased over the past decades because of their increasing use in such industries as textiles, paper, plastics, tannery and paints. These dyes can cause deterioration in water quality by imparting color to the water and inducing the photosynthetic activity of aquatic organisms by hindering light penetration. Moreover, some of the dyes are considered carcinogenic and mutagenic for human health. Therefore, efficient treatment and removal of dyes from wastewater have attracted considerable attention in recent years. Photoca…
In this paper, we perform theoretical study on the physical properties of two-dimensional transition metal chalcogenides MX$_{2}$ and M$_{2}$X$_{3}$ (M= Ni, Pd; X= S, Se, Te). These studied materials are classified in three stable phases according to their lattice structures: hexagonal MX$_{2}$, orthorhombic MX$_{2}$ and orthorhombic M$_{2}$X$_{3}$. They have either isotropic or anisotropic in-plane properties depending on their symmetries. In particular, the orthorhombic MX$_{2}$ and M$_{2}$X$_{3}$ have low lattice symmetry and present highly anisotropic properties. The orthorhombic MX$_{2}$ …
Photocatalytic water splitting is a promising renewable energy source as an alternative for limited fossil fuels. The effectiveness of the conversion from solar energy to hydrogen fuel relies primarily on the material. Previously, researchers studied different TMDs such as WS$_{2}$, and PdSe$_{2}$. These materials perform well in certain aspects such as strong adsorption stability and promising abilities for HER, however, their band gaps are still not ideal. In this paper, we studied a new TMD material WSe$_{2}$, which is currently used in heterostructure photocatalysts. To our knowledge, this…
To overcome current serious energy and environmental issues, photocatalytic water splitting holds great promise because it requires only solar energy as an energy input to produce hydrogen. Two-dimensional (2D) semiconductors and heterostructures possess several inherent advantages which are more suitable for boosting solar energy than their bulk counterparts. In this work, by performing high-throughput first-principles calculations combined with a semiempirical van der Waals dispersion correction, we first provided the periodic table of band alignment type for van der Waals heterostructures w…
Polar heterogeneous photocatalysts were shown to lead to enhanced charge-carrier separation that results in superior activity for example for photocatalytic water splitting. Promising photocatalyst materials such as oxynitrides can be rendered polar by epitaxial strain, which however also increases their band gap, making them unsuitable for visible light absorption. This suggests a trade-off between small band gaps and polar distortions - both being crucial for the catalyst's efficiency. In this paper we investigate, using density functional theory calculations, the suitability of strained AB(…
Photocatalytic water splitting can produce hydrogen in an environmentally friendly way and provide alternative energy sources to reduce global carbon emissions. Recently, monolayer fullerene networks have been successfully synthesized [Hou $\textit{et al., Nature}$ $\textbf{2022}$, 606, 507], offering new material candidates for photocatalysis because of their large surface area with abundant active sites, feasibility to be combined with other 2D materials to form heterojunctions, and the C$_{60}$ cages for potential hydrogen storage. However, efficient photocatalysts need a combination of a s…
Finding cost-effective and efficient photocatalytic materials able to catalyse the water splitting reaction under visible light is one of the greatest challenges in current environmental material science. Despite that many photocatalysts are already known in the context of green hydrogen production, strategies to systematically and rationally modify their optoelectronic properties to achieve desired photocatalytic performance are yet to be established. Piezoelectric materials react to mechanical stimuli by adjusting their band gaps and band alignments, thus offering a possible route to precise…
Photoelectrochemical (PEC) water splitting to generate hydrogen is one of the most studied methods for converting solar energy into clean fuel because of its simplicity and potentially low cost. Despite over 40 years of intensive research, PEC water splitting remains in its early stages with stable efficiencies far less than 10%, a benchmark for commercial applications. Here, we revealed that the desired photocorrosion stability sets a limit of 2.48 eV (relative to the normal hydrogen electrode (NHE)) for the highest possible potential of the valence band (VB) edge of a photocorrosion-resistan…
Two-dimensional (2D) materials viz. transition metal dichalcogenides (TMD) and transition metal oxides (TMO) offer a platform that allows creation of heterostructures with a variety of properties. The optoelectronic industry has observed an upheaval in the research arena of MoS$_2$ based van der Waals (vdW) heterostructures (HTSs) and Janus structures. Therefore, interest towards these structures are backed by the selectivity in terms of electronic and optical properties. The present study investigates the photocatalytic ability of bilayer, MoS$_2$ and Janus (MoSSe) based vdW HTSs viz. MoS$_2$…
Novel photoelectrocatalysts that use sunlight to power the CO$_2$ reduction reaction will be crucial for carbon-neutral power and energy-efficient industrial processes. Scalable photoelectrocatalysts must satisfy a stringent set of criteria, such as stability under operating conditions, product selectivity, and efficient light absorption. Two-dimensional materials can offer high specific surface area, tunability, and potential for heterostructuring, providing a fresh landscape of candidate catalysts. From a set of promising bulk CO$_2$ reduction photoelectrocatalysts, we screen for candidate m…
SrTiO$_3$ is a highly efficient photocatalyst for the overall water splitting reaction under UV irradiation. However, an atomic-level understanding of the active surface sites responsible for the oxidation and reduction reactions is still lacking. Here we present a unified experimental and computational account of the photocatalytic activity at the SrO- and TiO$_2$- terminations of aqueous-solvated [001] SrTiO$_3$. Our experimental findings show that the overall water-splitting reaction proceeds on the SrTiO$_3$ surface only when the two terminations are simultaneously exposed to water. Our si…
The production of hydrogen fuels, via water splitting, is of practical relevance for meeting global energy needs and mitigating the environmental consequences of fossil-fuel-based transportation. Water photoelectrolysis has been proposed as a viable approach for generating hydrogen, provided that stable and inexpensive photocatalysts with conversion efficiencies over 10% can be discovered, synthesized at scale, and successfully deployed (Pinaud et al., Energy Environ. Sci., 2013, 6, 1983). While a number of first-principles studies have focused on the data-driven discovery of photocatalysts, i…
Photocatalytic water splitting is an effective way to obtain renewable clean energy. The challenge is to design tunable photocatalyst to meet the needs in different environments. At the same time, the oxygen and hydrogen evolution reactions (OER and HER) on the photocatalyst should be separated, which will be conducive to the separation of products. The electronic, optical and photocatalytic properties of Janus X2PAs (X = Si, Ge and Sn) monolayers are explored by first-principles calculation. All the strain-free X2PAs monolayers exhibit excellent photocatalytic properties with suitable band ed…
The improved photocatalytic water splitting using 2D materials has technological importance for economically viable renewable energy. The present study focuses on the effect of uniaxial, biaxial, and vertical strain on the energy gap and band edge positions of C2N/MoS2 van der Waals heterostructures through first-principles density functional theory using PBE and SCAN functionals. The calculations establish that SCAN functional provides comparatively much better results as compared to the PBE for the band gap and band alignment study. The heterostructure exhibits a type- II band alignment whic…
Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects
掺杂石墨烯（GR）/半导体纳米复合材料的增强的光催化性能最近被广泛观察到，但对其背后的潜在机制的理解仍然遥不可及。作为研究掺杂效应的模型体系，我们采用第一性原理计算研究了掺杂GR/Ag 3 PO 4纳米复合材料的电子结构和光学性质，结果表明掺杂剂可以调节GR/Ag 3 PO 4（100）复合材料的带隙、近带隙电子结构和界面电荷转移.有趣的是，掺杂原子和键合到掺杂剂上的C原子由于相互作用引起的电荷重新分布而带正电荷或负电荷，因此成为掺杂剂的活性位点。掺杂可以增强可见光吸收和光生电子转移。我们认为，N原子可能是GR/Ag 3 PO 4光催化剂的最佳掺杂。该工作可以合理化现有的实验结果，N掺杂GR-半导体复合材料，并丰富了我们的理解掺杂GR基复合材料中的掺杂剂的作用，开发高性能的光催化剂。
TiO2 is a wide band-gap semiconductor that has been intensively investigated for photocatalysis and water-spiting. However, weak light absorption in the visible region of the spectrum poses stringent limitation to its practical application. Doping of TiO2 with N or transition-metal impurities has been explored to shift the onset of optical absorption to the visible region, yet with limited success. Based on hybrid density functional calculations, we propose adding Bi to TiO2, in the form of dilute Ti_(1-x)Bi_(x)O2 alloys, to efficiently shift the optical absorption to the visible region. Compa…
Two-dimensional vertically polarized Hg3AsSe4I monolayer for efficient photocatalytic water-splitting: promoting carrier separation by intrinsic electric field and Rashba effect
Frontier Institute of Science and Technology, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University（西安交通大学前沿科学研究所、电气绝缘与电源设备国家重点实验室）；Key Lab of advanced optoelectronic quantum architecture and measurement (MOE), Beijing Key Laboratory of Quantum Matter State Control and Ultra-Precision Measurement Technology, and School of Physics, Beijing Institute of Technology（北京理工大学物理学院、光电量子架构与测量教育部重点实验室、北京市量子物质态控制与超精密测量技术重点实验室）
Enhanced interfacial charge transfer by Z-scheme in defect-mediated ZnO-CdS nano-composite with rGO as a solid-state electron mediator for efficient photocatalytic applications
Boosting hydrogen and methane formation on a high-entropy photocatalyst by integrating atomic d0/d10 electronic junctions and microscopic P/N heterojunctions
High-entropy oxides (HEOs), as multi-component ceramics with high configurational entropy, have been of recent interest due to their attractive properties including photocatalytic activity for H2 production and CO2 conversion. However, the photocatalytic activity of HEOs is still limited to ultraviolet light. In this study, to achieve visible-light-driven photocatalysis, 10 different heterojunctions were simultaneously introduced in the Ti-Zr-Nb-Ta-W-O system. The oxide, which was synthesized by a high-pressure torsion method and oxidation, successfully produced oxygen from water under visible…
