A first-principles study of electronic structure and photocatalytic performance of two-dimensional van der Waals MTe2–As (M = Mo,W) heterostructures

To efficiently produce green energy and to overcome energy crises and environmental issues, photocatalytic water splitting has become the core heart of recent research. Fabricating heterostructures with type-II band alignment can enhance the photocatalytic activity. By first-principles computations, we study Mo(W)Te₂–As van der Waals (vdW) heterostructures as promising photocatalysts for overall water splitting. The bandgap, band edge position and optical properties can be modified by biaxial strain. With appropriate compressive strain of 2% and 3%, the WTe₂–As heterostructures show transition from type-I to type-II band alignment, which could slow down electron-hole pair recombination. Compared with Mo(W)Te₂ and As monolayers, the band edge of Mo(W)Te₂–As heterostructures is on favorable positions for straddling the water redox potentials. Moreover, Mo(W)Te₂–As heterostructures fascinatingly show strong absorption peaks in both visible and near ultra-violet region, making them promising candidates for overall water splitting photocatalysts.     

Constructing a new 2D Janus black phosphorus/SMoSe heterostructure for spontaneous wide-spectral-responsive photocatalytic overall water splitting

Janus MoSSe monolayer with built-in electric dipole, as another emerging two-dimensional (2D) material after MoS₂, is predicted to be an ideal photocatalyst for overall water splitting. However, in spite of the excellent hydrogen evolution reaction (HER) activity of Se-surface, the extremely poor oxygen evolution reaction (OER) activity of S-surface hinders the achievement of photocatalytic overall water splitting. Herein, we construct a new 2D van der Waals heterostructure consisting of high-OER-active black phosphorus (BP) and Janus MoSSe monolayer, and demonstrate a new strategy of Janus BP/SMoSe heterostructure to achieve wide-spectral-responsive photocatalytic overall water splitting. The electronic structures and optical properties of two different heterostructures, BP/SMoSe and BP/SeMoS, are systematically investigated via first principles density, exhibiting a type-II band arrangement. Unlike BP/SeMoS, the BP/SMoSe heterostructure shows excellent optical properties, such as a large dielectric constant of 8.14 and a small optical absorption boundary of 0.10 eV. Furthermore, BP/SMoSe heterostructure possesses greater light absorption intensity and a broader light absorption range. It is found that the BP/SMoSe heterostructure exhibits proper band alignment and enhanced intrinsic dipole, which is favorable to obtain high electron-hole separation efficiency. This work provides a feasible strategy of 2D Janus BP/SMoSe heterostructure for approaching almost perfect overall water-splitting photocatalysis.     

SiI2 monolayer as a promising photocatalyst for water splitting hydrogen production under the irradiation of solar light

The feasibility of SiI₂ monolayer as the candidate for photocatalytic water splitting for hydrogen generation under the irradiation of the solar light is explored. The geometrical structure, the electronic and optical properties, the mobility of carrier and strain engineering of the monolayer are investigated based on the first-principles calculations. The results demonstrate SiI₂ monolayer possesses an indirect gap of 2.33 eV (HSE06), and both the band edge and the bandgap match the redox potential conditions of the water splitting for hydrogen generation. There is an obvious optical absorption in the visible light and near-ultraviolet region and can be enhanced by the compressive strain. Moreover, the mobility of the electron is significantly different from that of the hole, implicating that the effective spatial charge separation is expectable and the ratio of the recombination of the photogenerated charge pairs is low. The primary adsorption site of the water molecule is identified. The Gibbs free energy and the adsorption energies are calculated to demonstrate the H₂ generation from the water molecule splitting on the monolayer. All the considered properties support that SiI₂ monolayer can be achieved as a promising candidate for the photocatalytic water splitting for hydrogen production under the irradiation of the solar light.     

New gallium chalcogenides/arsenene van der Waals heterostructures promising for photocatalytic water splitting

Single two-dimensional (2D) GaS and GaSe were studied as photocatalysts, yet the overall performance is limited by the low optical absorption and inefficient separation of photogenerated electron-hole pairs. Constructing van der Waals (vdW) heterostructures is an ideal way to overcome the deficiency of single 2D gallium chalcogenides. This work unravels that gallium chalcogenides/arsenene (GaX/As, X = S, Se) are the promising vdW heterostructures that show significantly improved photocatalytic performance by means of first-principles calculations. The GaX/As heterostructures possess suitable band alignment and bandgap satisfying the requirements for photocatalysts. Contrary to the pristine monolayers, the Se_0.5GaS_0.5/As and S_0.5GaSe_0.5/As heterostructures undergo indirect-direct bandgap transition by varying the interlayer distances; moreover, they exhibit high carrier mobility (～2000 cm² V^?1 s^?1 for electrons) and transport anisotropy, efficiently facilitating the migration and separation of photogenerated electron-hole pairs. Finally, all GaX/As heterostructures show significantly enhanced optical absorption beyond the isolated GaX monolayers under visible-light irradiation. These extraordinary properties render GaX/As heterostructures as competitive photocatalysts for water splitting to produce hydrogen.     

Two dimensional Janus SGaInSe(SeGaInS)/PtSe2 van der Waals heterostructures for optoelectronic and photocatalytic water splitting applications

Hydrogen generation by photocatalytic water splitting is considered as a viable and clean energy source for dealing with energy shortages and environmental pollution challenges. By means of first-principles calculations, the SGaInSe(SeGaInS)/PtSe₂ van der Waals (vdWs) heterostructures are confirmed to be energetically, dynamically, and thermally stable, indicating that they have a lot of potential for experimental implementation. The Model-I of SGaInSe/PtSe₂ heterostructures possesses type-II indirect band alignment, while the other three heterostructures retain type-I band alignment, which is further tuned to type-II with the application of strain. The charge transfer to SGaInSe/SeGaInS layer from PtSe₂ layer generates built-in electric field that effectively resists the recombination of photo-generated electron-hole pairs. At pH = 0, the band edge positions of both heterostructures completely straddle the redox potentials. The Model-I of SeGaInS/PtSe₂ heterostructures with biaxial ?2% compressive strain makes the band edges to do complete water splitting in natural environment (pH = 7). In the visible range of the irradiating spectrum, our designed heterostructures have enhanced imaginary part of the dielectric function and absorption coefficient up to 10⁵ cm^?1. Moreover, with the biaxial compressive (tensile) strains, the blue-shift (red-shift) in absorption spectra is examined. Our study extends the applications of Janus monochalcogenides/PtSe₂ vdWs heterostructures and supports to design of more heterostructures-based photocatalysts and optoelectronic devices.     

A review on copper vanadate‐based nanostructures for photocatalysis energy production

The economic, social, and environmental aspects are important that should be notable before the selection of a method for the production of energy. Various renewable energy sources are used like hydropower, biomass, biofuel, geothermal energy, and wind energy for the production of sustainable energy that are excellent approaches to fulfill energy environmental energy demands. Renewable sources of energy give an excellent chance to extenuate the gas emission in greenhouse and reduction of global warming with the help of renewable sources of energy. The importance and utilization of the variety of renewable sources of energy are elaborated in this article. The emerging and exploring technique for the production of energy is the photocatalysis. In photocatalysis, solar spectrum is the extraneous source that is used with water to produce hydrogen energy (green energy) by the water splitting under the shower of the solar spectrum. The solar spectrum contains heat and intensity of light from which light spectrum is the abundantly used for the splitting of water. The photocatalyst is the key factor to initiate the reaction depending upon the energy band gap by absorbing the energy from the spectrum of the sun. Semiconducting materials having lower forbidden energy band gap are the basic requirements to use them as a photocatalyst for photocatalysis. Copper vanadate and their composites are the promising materials that are used as photocatalyst for the production of hydrogen energy. Copper vanadate is the focusing material that can be used as photocatalyst. It is an n‐type semiconducting material with 2 eV indirect energy band gap having monoclinic structural phase which is tuned by the doping of metals like chromium, molybdenum, and silver to reduce the grain size and energy band gap and increase the surface area and optical absorption of solar light only to enhance the photocatalytic performance towards the production of hydrogen energy by water splitting in the presence of solar light.     

等离激元效应促进的光催化分解水制氢

  目的  利用光催化分解水的方式直接将太阳能转化并存储为氢气的化学能,是发展清洁能源促进低碳经济的有效途径。文章围绕等离激元效应对光催化分解水制氢的促进机理进行综述,以推进其产业化应用。  方法  阐释了等离激元效应在光催化分解水反应过程中的微观机制,分析了等离激元粒子在增强太阳光的吸收能力、拓展吸收光谱的响应范围、促进光生电子空穴的分离、提升光生载流子的热力学能、以及提供光催化反应活性中心等方面发挥的重要作用。  结果  通过总结当前等离激元效应促进光催化分解水制氢的研究进展,浅析了目前存在的问题,并对该领域的未来发展趋势进行了展望。  结论  基于等离激元效应在太阳能生产燃料中的巨大应用潜力,不同学科背景的相关学者协同合作,对影响光催化剂效率和寿命的各项决定性因素积极研发攻关,将促进该技术领域获得重要突破。     

Theoretical design of a novel 2D tetragonal ZnS/SnO hetero-bilayer as a promising photocatalyst for solar water splitting

Van der Waals (vdW) hetero-bilayers are emerging as unique structures to enhance the performance of two-dimensional (2D) layered nanomaterials for next-generation electronic and optoelectronic devices. In this work, we employ first-principles calculations to study the novel tetragonal ZnS/SnO hetero-bilayer (BL). The state-of-the-art computations based upon quasiparticle GW and Bethe−Salpeter equation (BSE) are utilized to study the electronic and optical properties of this novel vdW hetero-bilayer. We reveal that ZnS/SnO BL is a polarized semiconductor with a clear built-in electric field, and possesses a special band characteristic favorable for reducing the carrier recombination. It is also demonstrated that strain and external electric field are among the effective methods to modulate the electronic and optical properties of ZnS/SnO BL. Our work suggests that ZnS/SnO BL has an excellent optical absorption in the solar spectrum, rendering the material a viable candidate for optoelectronic applications, in particular for solar water splitting.     

Efficient band structure tuning of single-layer group IV-N semiconductors for visible-light-driven water splitting

Discovering more novel two-dimensional (2D) materials for solar water splitting has long been an essential topic in photocatalysis. The present study employs the hybrid functional (HSE06) theory to systematically investigate the electronic structures and band alignments with respect to the water redox potential of the mono-doping (cationic C and anionic P) and co-doping (B + O, B + S, Al + O, Al + S, and C + P) in monolayer IV-N (IVSi, Ge, and Sn) semiconductors. These donor-acceptor doping pairs are charge-compensated so that the doping systems can keep semiconductor character without recombination centers. Importantly, we discovered several co-doped IV-N structures to be highly promising solar water splitting photocatalysts, including (B + S) co-doped SiN, and (B + O), (B + S), and (C + P) co-doped GeN. They possess ideal band gaps (～2.0 eV) for the maximum utilization of solar light, suitable band positions for the water redox reactions, and enhanced visible light response. Moreover, we propose that the band gap of the monolayer IV-N can be slightly reduced by the (Al + S) or (Al + O) co-doping, while heavily tailed by the (B + O) or (B + S) co-doping. Our research provides valuable insights for designing and synthesizing novel 2D IV-N photocatalysts for solar water splitting.     

Indirect Z-scheme hydrogen production photocatalyst based on two-dimensional GeC/MoSi2N4 van der Waals heterostructures

The stacked two-dimensional materials with suitable band gap are crucial for photocatalytic hydrogen production. Here, using first-principles calculations, the GeC/MoSi₂N₄ heterojunction with a band gap of 1.80 eV is calculated thoroughly. The indirect band alignment of Z-scheme and high carrier mobility boost the separation of electron-hole pairs, allowing more electrons and holes participating in the reactions. Additionally, the band-edge potential perfectly satisfies the requirements for redox potential of water splitting. Furthermore, the Gibbs free energy (−0.552 eV) close to zero indicates the heterojunction can conduct HER exceedingly well, providing a guarantee for photocatalytic hydrogen production. Remarkably, the light absorption coefficient peak is about 1.39 × 10⁵ cm⁻¹ within the visible light range enables the heterojunction to absorb more visible light from the spectrum. In short, results demonstrate the GeC/MoSi₂N₄ heterojunction is a promising photocatalyst for visible light water splitting, which will pave the way for the development of water splitting hydrogen production.     

PtS2/g-C3N4 van der Waals heterostructure: A direct Z-scheme photocatalyst with high optical absorption,solar-to-hydrogen efficiency and catalytic activity

Using two-dimensional semiconductors to build heterojunction as photocatalyst for water splitting is an important green and clean energy technology and has wide development prospects. Here, the monolayered PtS₂ and g-C₃N₄ are used to build the direct Z-scheme van der Waals (vdW) heterostructure, and the structure, electrical, Bader charge, optical properties and solar-to-hydrogen efficiency are calculated in detail through first-principle calculations. The direct Z-scheme PtS₂/g-C₃N₄ vdW heterostructure has an inherent type-II band alignment that enables it to reduce the photogenerated carriers aggregation, and it also possesses a decent band edge position to fully induce the redox reactions of decomposed water. The charge density shows that PtS₂ monolayer is negatively charged while g-C₃N₄ monolayer is positively charged, and the interface potential drop of PtS₂/g-C₃N₄ vdW heterostructure forms a built-in electric field with the direction from g-C₃N₄ to PtS₂. The PtS₂/g-C₃N₄ vdW heterostructure has suitable optical property, outstanding solar-to-hydrogen efficiency, high catalytic activity and thus a promising application prospect for photocatalytic water splitting.     

Janus Ga2SeTe and In2SeTe nanosheets: Excellent photocatalysts for hydrogen production under neutral pH

In the past few years, Janus nanosheets have attracted much interest according to their specific structure and considerable potential to address the energy and environmental issues. Herein, the electronic, optical and photocatalytic properties of two-dimensional Janus Ga₂SeTe and In₂SeTe have been studied using ab-initio computations based on the density functional theory. The obtained results show that these nanomaterials exhibit a semiconductor behavior with direct and moderate bandgaps using hybrid HSE06 functional. Subsequently, the understudied compounds present suitable optical conductivity, absorption, transmission and reflectivity for water splitting under the ultraviolet–visible light irradiation. Interestingly, the band edge positions of Janus Ga₂SeTe and In₂SeTe excellently straddle the redox potentials of water under neutral pH. Additionally, the free energy values for the formation of H₂ from H adsorbed on the Ga₂SeTe and In₂SeTe compounds are respectively 1.304eV and 0.976eV at pH = 7. More excitingly, the present study proposes strain engineering approach to improve the photocatalytic performance of the Janus Ga₂SeTe and In₂SeTe monolayers. Specifically, the investigated semiconductors show more appropriate band edge alignment and better hydrogen evolution reaction activity under biaxial tensile strain, which fulfil the water splitting requirements at neutral pH conditions. Our findings conclude that the Janus Ga₂SeTe and In₂SeTe nanosheets are promising candidates for photocatalytic hydrogen production.     

Hydrogen evolution from solar water splitting on nanostructured copper oxide photocathodes

Copper oxide has received much attention as a photocatalyst for solar water splitting, since it has a band gap of ～2.0?eV with favourable energy band positions for water cleavage; it is abundant and environmentally friendly. In this paper, we report the preparation of copper oxide thin films on copper substrate with different morphology by a solution route in large scales. The method was simple, low cost, and can be completed in the absence of any surfactant. Copper oxide films were characterised by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD analysis and FT-IR analysis confirm the formation of copper oxide films. SEM images show gradual development of hierarchical structures of copper oxide with different morphology. The films were successfully tested as photocathodes in a photoelectrochemical cell, and their photocatalytic activity was evaluated by testing the solar water splitting. The photocatalytic activity of these films was found to be size-dependent and films with smaller dimensions demonstrated a significant increase in photocatalytic activities during solar water splitting process. Based on the above discussion, we believe that these samples are attractive candidates as a visible-light-driven photocatalyst.     

Theoretical insights into the origin of highly efficient photocatalyst NiO/NaTaO3 for overall water splitting

NaTaO₃ loaded with NiO cocatalyst is one of the few photocatalysts for overall water splitting in UV region, which have attracted much attention. In this work, density functional theory calculations have been performed to investigate the interfacial geometries, electronic structures, charge transport, optical absorptions and band offsets of NiO(001)/NaTaO₃(001) slab models. By considering possible terminations of NaTaO₃(001) surface, two heterostructures denoted as NiO/TaO₂ and NiO/NaO have been constructed. Our results show that two kinds of contact are thermodynamically stable, and there is a stronger rumpling of atomic layers appearing in NiO/NaO than NiO/TaO₂. The calculated band structures reveal that NiO(001)/NaTaO₃(001) interfaces have indirect band gaps. The mobilities of photoinduced charge carriers in interfacial structures are faster than those in pure surfaces. NiO/TaO₂ has a higher mobility and lower recombination rate of photogenerated electrons and holes than NiO/NaO. Loading NiO on NaTaO₃ surface has a negligible effect on the extension of light absorption, which is consistent with experiments. Both heterostructures form a Type-II band alignment. The difference of electrostatic potentials around the interface as a driving force boosts the migration of electrons and holes to different domains of the interface, which is beneficial to extend the lifetime of photoinduced carriers and improve the photocatalytic activity of NaTaO₃ system. NiO/TaO₂ has the ability of overall splitting water with NiO as the oxidation cocatalyst, while in NiO/NaO, the photogenerated electrons and holes are accumulated on NiO and NaO side, respectively. Our results demonstrate that the function of NiO in NiO/NaTaO₃ photocatalytic system is determined by the termination property of NaTaO₃(001) surface, which may be one possible reason why it is difficult to ascertain whether NiO is a proton reduction cocatalyst or water oxidation cocatalyst experimentally.     

Type-II AsP/Sc2CO2 van der Waals heterostructure: an excellent photocatalyst for overall water splitting

In this work, we explore the application potential of AsP/M₂CO₂ (M = Sc, Zr) van der Waals heterostructures in photocatalytic water splitting through the first-principles calculations. The calculated results show that AsP/Zr₂CO₂ heterostructure possesses an unfavorable type-Ⅰ band alignment, whereas AsP/Sc₂CO₂ exhibits a desirable type-Ⅱ band alignment, which is beneficial for separating the photogenerated electron-hole pairs. Also, the band edge positions of AsP/Sc₂CO₂ heterostructure stride the redox potential of water, ensuring favorable reaction kinetics. Besides, the strong optical absorption of AsP/Sc₂CO₂ heterostructure in both visible and ultraviolet regions (especially up to 10⁻⁶ cm⁻¹ at about 250 nm) makes it possible to utilize solar energy effectively. Meanwhile, AsP/Sc₂CO₂ heterostructure has an exciton binding energy as low as 0.09 eV, which quantitatively illustrates the high separation efficiency of photogenerated charge carrier. Thus, the type-Ⅱ band alignment, suitable band edge position, strong light absorption, and low exciton binding energy together indicate that AsP/Sc₂CO₂ heterostructure is a potential photocatalytic material. In addition, the obvious redshift phenomenon in the optical spectrum of AsP/Sc₂CO₂ heterostructure shows that biaxial strain can improve its light capture capability. Also, the interconversion between type-Ⅱ and type-Ⅰ can be achieved by applying different strains. All these findings suggest that the novel AsP/Sc₂CO₂ heterostructure has significant application prospects in next-generation photovoltaic and photocatalytic devices.     

Promising photocatalysts with high carrier mobility for water splitting in monolayer Ge2P4S2 and Ge2As4S2

Monolayer Ge₂P₄S₂ and Ge₂As₄S₂ are proposed as a new type of efficient photocatalyst for water splitting, based on first-principles calculations. Monolayer Ge₂As₄S₂ exhibits a direct band gap of 1.89 eV (based on HSE06 calculation), while monolayer Ge₂P₄S₂ is an indirect gap semiconductor that can turn into direct band gap by applying 3% compressive strain. Moreover, the band edge positions of monolayer Ge₂P₄S₂ and Ge₂As₄S₂ perfectly cover the redox potentials of water. Remarkably, the Ge₂P₄S₂ and Ge₂As₄S₂ monolayers possess rather high carrier mobilities (∼10³–10⁴ cm² V⁻¹ s⁻¹), and have moderate optical absorption performance in the range of visible light. In addition, the adsorption and decomposition of water molecules on monolayer Ge₂P₄S₂ and Ge₂As₄S₂ are explored to illustrate the mechanism of photocatalytic hydrogen formation. These results demonstrate that the monolayer Ge₂P₄S₂ and Ge₂As₄S₂ hold great potential for photocatalytic water splitting.     

A current perspective for photocatalysis towards the hydrogen production from biomass-derived organic substances and water

Recently, an increasing interest has been devoted to produce chemical energy – hydrogen (H₂) by converting sustainable sunlight energy via water splitting and reforming of renewable biomass-derived organic substances. These photocatalytic processes are very promising, sustainable, economic, and environment-friendly. Herein, this article gives a concise overview of photocatalysis to produce H₂ as solar fuel via two approaches: water splitting and reforming of biomass-derived organic substances. For the first approach – photocatalytic water splitting, there are two reaction types have been used, including photoelectrochemical (PEC) and photochemical (PC) cell reactions. For the second approach, biomass-derived oxygenated substrates could undergo selective photocatalytic reforming under renewable solar irradiation. Significant efforts to date have been made for photocatalysts design at the molecular level that can efficiently utilize solar energy and optimize the reaction conditions, including light irradiation, type of sacrificial reagents. Critical challenges, prospects, and the requirement to give more attention to photocatalysis for producing H₂ are also highlighted.     

A perspective on the fabrication of heterogeneous photocatalysts for enhanced hydrogen production

This perspective provides an insight to the possibility of adopting hydrogen as a key energy-carrier and fuel source, through Photocatalytic water splitting in the near future. The need of green and clean energy is increasing to overcome the growing demand of sustainable energy throughout globe, owing to CO₂ emission using fossil fuels. To generate highly efficient and cost-competitive hydrogen, the semiconductor based heterojunction nanomaterials have gained tremendous consideration as a promising way. Currently, the efficiency for hydrogen generation through UV–Vis active photocatalysts is relatively low. The key issues are found to be poor separation of photogenerated electron/hole, less surface area, and low absorption region of electromagnetic spectrum. Such issues arise due to inappropriate band edge potentials and large bandgap of present catalyst. A lot of schemes has been devoted to design and fabricate efficient photocatalysts for improved photocatalytic performance in recent years. However, it seems still a challenge and imperative to greatly comprehend the fundamental aspects, photocatalysis and transfer mechanisms for complete deployment of electron/hole pairs. Further, to produce hydrogen to a larger extent through photocatalytic water splitting, the photocatalyst has been modified through co-catalysts/dopants using numerous techniques including the Z-scheme, hybridization, crystallinity, morphology, tuning of band edge positions, reduction of the band gap, surface structure etc., such that these heterogeneous photocatalysts may have ability to absorb enough light in the UV-VIS-IR region. This type of heterogeneous photocatalysts has the ability to improve the rate of efficiency for hydrogen evolution through absorption of sufficient light of solar spectrum and enhance the separation of charge-carriers by inhibiting recombination of electron/hole pairs. We surmise that taking into account the aforesaid factors should support in scheming an efficient photocatalysts for hydrogen production through water splitting, eventually prompting technological developments in this field.     

The interfacial charge transfer in triphenylphosphine-based COF/PCN heterojunctions and its promotional effects on photocatalytic hydrogen evolution

In this study, the novel triphenylphosphine-based covalent organic frameworks (P–COF-1) were firstly introduced into polymeric carbon nitride (PCN) to fabricate P–COF-1/PCN heterojunctions via intermolecular π-π interaction. The photocatalytic H₂ production rate over the 9% P–COF-1/PCN heterojunctions is ca. 12 times as much as that of pure PCN. The photoelectrochemical measurements and theoretical calculation results show that due to the well-matched band structure between P–COF-1 and PCN, the photo-generated electrons tend to migrate from P–COF-1 into the conduction band of PCN through the interface of heterostructures. In addition to the π→π1 electron transition of conjugated tri-s-triazine units in the 9% P–COF-1/PCN with band gap energy of 2.53 eV, the lone pair electrons of P transition to the π1 orbitals of P–COF-1 (n→π1) with lower band gap energy of 1.82 eV results in the effective separation of photo-generated carriers and more visible light absorption, and thus enhanced the photocatalytic hydrogen evolution.     

Reduced band gap & charge recombination rate in Se doped α-Bi2O3 leads to enhanced photoelectrochemical and photocatalytic performance: Theoretical & experimental insight

For better utilization of solar spectrum and complete redox of water for water splitting applications, it is required to have a semiconductor which is photoactive in visible region. In this study, we report theoretical and experimental investigations on morphological and opto-electronic modifications induced in α-Bi₂O₃ due to Selenium (Se) doping tested for photoelectrochemical (PEC) & photocatalytic properties. Density Functional Theory (DFT) calculations revealed band gap reduction and direct to indirect transitions in Se-doped α-Bi₂O_3. This reduction in band gap is attributed to hybridization of Se p & Bi s in valence band and Se d & Bi p orbital in conduction band. To support this finding experimentally, we synthesized Se-doped α-Bi₂O₃ using simple chemical precipitation method and measured its band gap using photoluminescence and UV–Vis spectroscopy. Experimental results also confirmed the reduction in band gap energy and recombination rate of charge carriers as compared to pristine α-Bi₂O₃ sample. PEC study of Se-doped α-Bi₂O₃ showed an increased photocurrent density, charge carrier density and lowered impedance, which indicates its efficient solar spectrum utilization and better hydrogen generation efficiency. Photocatalytic measurement also revealed higher rate of dye degradation with Se doped α-Bi₂O₃.