Solar Energy Conversion Research Articles

Hot carriers from intra- and interband transitions in gold-silver alloy nanoparticles

Hot electrons and holes generated from the decay of localised surface plasmons in metallic nanoparticles can be harnessed for applications in solar energy conversion and sensing. In this paper, we study the generation of hot carriers in large spherical gold-silver alloy nanoparticles using a recently developed atomistic modelling approach that combines a solution of Maxwell’s equations with large-scale tight-binding simulations. We find that hot-carrier properties depend sensitively on the alloy composition. Specifically, nanoparticles with a large gold fraction produce hot carriers under visible light illumination while nanoparticles with a large silver fraction require higher photon energies to produce hot carriers. Moreover, most hot carriers in nanoparticles with a large gold fraction originate from interband transitions which give rise to energetic holes and ‘cold’ electrons near the Fermi level. Increasing the silver fraction enhances the generation rate of hot carriers from intraband transitions which produce energetic electrons and ‘cold’ holes. These findings demonstrate that alloy composition is a powerful tuning parameter for the design of nanoparticles for applications in solar energy conversion and sensing that require precise control of hot-carrier properties.

Optimal Design Of The Concentric Annulus For The Solar Collectors And Energy Storage

Heat exchangers with uniform heating ensure even heat distribution, improving heat transfer efficiency and lowering thermal stress. It contributes to increasing the effectiveness of solar energy conversion into thermal energy in solar collectors, improving system performance and sustainability. It is essential for enhancing performance in both home and industrial applications because of these advantages. An experimental investigation was conducted to study the natural convective flow between two isothermal concentric cylinders filled with porous media (silica sand) and equipped with annular fins attached to the inner cylinder. The fins varied in length (Hf = 3, 7, and 11 mm), and the radius ratios (Rr) between the cylinders were also considered during the study. This work examines and discusses the effects of independent characteristics, such as fin height (Hf), radius ratio (Rr), and Rayleigh number (Ra) from 10 to 500, on heat transfer outcomes. As the distance between the two cylinders expands, the average Nu remains relatively constant for low values of Ra. However, as Ra approaches 100, the average Nu increases. These values also rose when Rr decreased for the hot cylinder and vice versa for the cold cylinder. The average Nusselt number versus Ra was analyzed in graphical form to show the effect of the fin number on the average Nusselt number. The analysis includes a range of fin numbers. It is found that as the amount of fins increases from n = 12 to n = 23 and eventually to n = 45, there is a decrease in the average Nusselt number. The decrease in average Nusselt number can range from 19.2% to 26.6% for the same value of Ra.

Experimental investigation of dual-slope and pyramid structural solar stills with various latent heat absorption materials for enhanced solar energy conversion

Experimental investigation of dual-slope and pyramid structural solar stills with various latent heat absorption materials for enhanced solar energy conversion

Constructing magnetically propelled piezoelectric and pyroelectric bifunctional micromotors to boost the photocatalytic H2 production involving biomass reforming

Biomass-assisted photocatalytic water splitting for hydrogen (H2) production has attracted widespread interest, which is important for the development of green H2 energy and the high value-added utilization of biomass. Although photothermal utilization can improve solar energy conversion efficiency, the elevated temperature also enhances the likelihood of electron-hole collisions. Herein, magnetically propelled PVDF/Fe3O4@g-C3N4 spiral micromotors were constructed to easily foster the synergistic coupling of piezoelectric and pyroelectric effects, which is beneficial to enhance the directional migration of photogenerated carriers at high temperatures. With both piezo- and pyroelectric effects, the biomass glucose involved H2 production rate on PVDF/Fe3O4@g-C3N4 spiral micromotors is 42.3 μmol/h, representing a significant increase of 31.9 times compared to water splitting without these effects, and the average apparent quantum yield at ordinary pressure can reach 12.6 %. Furthermore, photoluminescence and variable-temperature electrochemistry demonstrate that the piezo-pyroelectric coupling can accelerate the separation of carriers. Meanwhile, COMSOL simulations and KPFM tests show that the built-in electric field of the sample is enhanced under the piezo-pyroelectric effect. The spiral micromotors can easily realize the synergism of piezoelectric and pyroelectric effects, which provides an effective strategy to enhance the built-in electric field and thereby improve the performance of photocatalytic H2 evolution involving biomass reforming.

Synergistic enhancement of metal–organic framework-derived hierarchical porous materials towards photothermal conversion and storage properties of phase change materials

The design and synthesis of composite phase change materials that integrate photothermal conversion and latent heat storage have guiding significance for the efficient development and utilisation of solar energy. In this study, taking into consideration the advantages of metal–organic frameworks (MOFs) with adjustable structure and properties, HKUST-1-derived CuO/hierarchical porous carbon materials were employed and integrated with palmitic acid (PA) to synthesise composite phase change materials that exhibit exceptional comprehensive properties. The effects of different carbonation temperatures on HKUST-1-derived CuO/hierarchical porous carbon were analysed through a series of characterisations. The hierarchical porous structure in the blended system offers abundant pore structure and high specific surface area to prevent leakage of phase change materials. Composite phase change materials can maintain good shape stability and excellent thermal energy storage capacity. The thermal storage efficiency and photothermal conversion efficiency are 98.28% and 81.83%, respectively. Meanwhile, the thermal conductivity of the composite phase change material is 3.65 times that of pure PA. In conclusion, the MOFs derivative-based composite phase change materials designed in this study exhibited potential for thermal energy storage and can be applied to the field of solar energy conversion and storage systems.

Synergistic effect in ZIF-67/MoS2 entrenched MWCNT photo (electro) catalyst for degradation of tetracycline and alternative to Pt counter electrode in dye-sensitized solar cells

Photocatalytic water purification is an effective environmental protection approach for removing hazardous chemicals in water, besides solar energy conversion is a trustworthy and sustainable choice for the future due to rising energy demands. The present research focus is on synthesis of Metal-Organic Framework (MOF) based composite, Zeolitic Imidazolate Framework-67/Molybdenum Disulfide (ZIF-67/MoS2) entrenched Multi-Walled Carbon Nanotubes (MWCNT) as a catalyst for photodegradation of tetracycline (TC), as well as substitute for Pt counter electrode in Dye-Sensitized Solar Cell (DSSC). The crystalline structure, optical response, shape, porosity, quantum states, and chemical configuration were determined using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-DRS), Photoluminescence spectroscopy (PL), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), and X-ray Photoelectron Spectroscopy (XPS), respectively. The degradation efficiency of ZIF-67/MoS2/MWCNT catalyst under effect of operational parameters namely, photocatalyst dosage, solution pH, coexisting ions, TC concentrations and irradiation time were studied consecutively. ZIF-67/MoS2/MWCNT composite achieved 96.1 % degradation efficiency of TC under white light irradiation. Interestingly, when utilized as a counter electrode in DSSCs, this composite-based electrode delivered the highest Power Conversion Efficiency (PCE) of 3.86 % with a short-circuit current density (JSC) of 7.54 mA cm−2 and open-circuit voltage (VOC) of 0.79 V. The observed enhancement is attributed to lesser peak-to-peak separation (EPP), lower electron lifetime, lower charge transfer resistance (RCT) and higher exchange current density (J0). Based on these findings, ZIF-67 inclusion in MoS2/MWCNT composite is not only an effective catalyst for water treatment but also a good catalyst for I3− reduction in DSSCs.

Ultrafast Excited-State Energy Transfer in Phenylene Ethynylene Dendrimer: Quantum Dynamics with the Tensor Network Method.

Photoinduced excited-state energy transfer (EET) processes play an important role in solar energy conversions. Owing to their excellent photoharvesting and exciton-transport properties, phenylene ethynylene (PE) dendrimers display great potential for improving the efficiency of solar cells. In this work, we investigated the intramolecular EET dynamics in a dendrimer composed of two linear PE units (2-ring and 3-ring) using a fully quantum description based on the tensor network method. We first constructed a diabatic model Hamiltonian based on the electronic structure calculations. Using this diabatic vibronic coupling model, we tried to obtain the main features of the EET dynamics in terms of the several diabatic models with different numbers of vibrational modes (from 4 modes to 129 modes) and to explore the corresponding vibronic coupling interactions. The results show that the EET in this PE dendrimer is ultrafast. Four modes of A' symmetry play dominant roles in the dynamics; the remaining 86 modes of A' symmetry can dampen the electronic coherence; and the modes of A″ symmetry do not exhibit significant influence on the EET process. Overall, the first-order intrastate vibronic coupling terms show the dominant role in the EET dynamics, while the second-order intrastate vibronic coupling terms cause damping of the electronic coherence and slow down the overall EET process. This work provides a microscopic understanding of the EET dynamics in PE dendrimers.

Highly Efficient Photoelectrochemical Alkene Epoxidation on a Dye-Sensitized Photoanode.

In photoelectrochemical (PEC) cells, selective oxidation of organic substrates coupled with hydrogen evolution represents a promising approach for value-added chemical production and solar energy conversion. In this study, we report on PEC epoxidation of alkenes at a ruthenium dye-sensitized photoanode in a CH3CN/H2O mixed solvent with LiBr as a mediator and water as the oxygen source. The dye-sensitized photoanode was found to exhibit significant advantages in the simultaneous improvement of charge separation and suppression of charge recombination. First, LiBr as a redox mediator plays a critical role in charge separation, leading to an excellent excited electron injection efficiency of 95% and a high dye regeneration efficiency of 87%. Second, the predominant charge recombination pathway on the dye-sensitized photoanode is efficiently blocked by the reaction between alkene and the in situ generated bromine oxidant. As a result, the current system achieved a remarkable photocurrent density of over 4 mA cm-2 with a record-high incident photo-to-current efficiency (IPCE) of 51% and extraordinary selectivity of up to 99% for the epoxidation of a wide range of alkenes. Meanwhile, nearly 100% Faradaic efficiency for hydrogen evolution was obtained. The performance shown here exceeds that obtained by metal oxide-based semiconductor photoanodes under comparable conditions, demonstrating the great potential of dye-sensitized photoelectrodes for organic synthesis owing to their diversity and tunability.

Regulation of morphology and charge transfer mechanism: Oxygen vacancy-rich Mn0.2Cd0.8S/CoMoO4 S-type heterojunction promoting photocatalytic hydrogen production through hydrothermal in-situ synthesis

The development of efficient photocatalysts is a very interesting topic for sustainable hydrogen production using solar energy. In this paper, Mn0.2Cd0.8S was loaded on CoMoO4 nanorods by in-situ solvothermal method. Through morphological control, two rod-shaped elemental materials were loaded in situ to construct a composite with a ball shaped bouquet structure. The Mn0.2Cd0.8S/CoMoO4 photocatalyst with enriched oxygen vacancies was synthesized by high-temperature annealing. It is worth noting that by constructing an heterojunction, the Mn0.2Cd0.8S/CoMoO4 photocatalyst exhibits high catalytic activity and stability. The optimal H2 production rate of Mn0.2Cd0.8S/CoMoO4 was 7.04 mmol·g−1·h−1. Surprisingly, the hydrogen production rate of the composite was 35.88 times that of CoMoO4. Density functional theory (DFT) calculations showed that Mn0.2Cd0.8S/CoMoO4 has electron attraction ability and strong conductivity. X-ray photoelectron spectroscopy (XPS) confirmed the charge transfer path of the heterojunction between Mn0.2Cd0.8S and CoMoO4, which greatly promoted the spatial charge separation. This work provides a reference for combining heterojunction design with defect engineering to achieve efficient conversion of solar energy to chemical energy.

Directional Electron Flow in a Selenoviologen-Based Tetracationic Cyclophane for Enhanced Visible-Light-Driven Hydrogen Evolution.

Directional electron flow in the photocatalyst enables efficient charge separation, which is essential for efficient photocatalysis of H2 production. Here, we report a novel class of tetracationic cyclophanes (7) incorporating bipyridine Pt(II) and selenoviologen. X-ray single-crystal structures reveal that 7 not only fixes the distances and spatial positions between its individual units but also exhibits a box-like rigid electron-deficient cavity. Moreover, host-guest recognition phenomena are observed between 7 and ferrocene, forming host-guest complexes with a 1:1stoichiometryin MeCN. 7exhibits good redox properties, narrow energy gaps, and strong absorption in the visible range (370-500 nm) due to containing two selenoviologen(SeV2+)units.Meanwhile, the femtosecond transient absorption (fs-TA) reveals that 7 has stabilized dicationic biradical, efficient charge separation, and facilitates directional electron flow to achieve efficient electron transfer due to the formation of rigid cyclophane and electronic architecture. Then, 7 is applied to visible-light-driven hydrogen evolution with high hydrogen production (132 μmol), generation rate (11 μmol/h),turnover number (221), and apparent quantum yield (1.7%), which provides a simplified and efficient photocatalytic strategy for solar energy conversion.

Directional Electron Flow in a Selenoviologen‐Based Tetracationic Cyclophane for Enhanced Visible‐Light‐Driven Hydrogen Evolution

Directional electron flow in the photocatalyst enables efficient charge separation, which is essential for efficient photocatalysis of H2 production. Here, we report a novel class of tetracationic cyclophanes (7) incorporating bipyridine Pt(II) and selenoviologen. X‐ray single‐crystal structures reveal that 7 not only fixes the distances and spatial positions between its individual units but also exhibits a box‐like rigid electron‐deficient cavity. Moreover, host‐guest recognition phenomena are observed between 7 and ferrocene, forming host‐guest complexes with a 1:1 stoichiometry in MeCN. 7 exhibits good redox properties, narrow energy gaps, and strong absorption in the visible range (370‐500 nm) due to containing two selenoviologen (SeV2+) units. Meanwhile, the femtosecond transient absorption (fs‐TA) reveals that 7 has stabilized dicationic biradical, efficient charge separation, and facilitates directional electron flow to achieve efficient electron transfer due to the formation of rigid cyclophane and electronic architecture. Then, 7 is applied to visible‐light‐driven hydrogen evolution with high hydrogen production (132 μmol), generation rate (11 μmol/h), turnover number (221), and apparent quantum yield (1.7%), which provides a simplified and efficient photocatalytic strategy for solar energy conversion.

Tuning the essential physical properties of KTaO3 through sulfur, selenium doping, and oxygen vacancy: A first principle investigation

The objective of this work is to use density functional theory (DFT) analysis to explain the effects of sulfur (S), selenium (Se), and oxygen vacancies on the mechanical, electrical, optical, dynamical, and thermoelectric properties of KTaO3. Our investigation has uncovered important modifications to KTaO3 many characteristics, most notably to its band gap values. Crucially, every chemical that was studied showed evidence of both dynamical and mechanical stability. These compounds are also good prospects for a variety of optoelectronic applications due to their promising optical properties, which include strong optical conductivity throughout the visible spectrum, low reflection, and high absorption coefficients. Our thorough analysis has shown the remarkable electrical, optical, and mechanical characteristics, including high absorptivity, low reflectivity, hardness, ductility, and semiconducting behavior. It has also highlighted the stability of all computed phases. The optical characteristics and adjusted band gap of KTaO3 indicate that it has substantial potential for use in solar cells, providing avenues for improving the efficiency of solar energy conversion. In addition, the exceptional heat conductivity of KTaO3 offers exciting opportunities for its use as a heat sink material.

Designing copper-doped zinc oxide nanoparticle by tobacco stem extract-mediated green synthesis for solar cell efficiency and photocatalytic degradation of methylene blue

This study presents the green synthesis of copper-doped zinc oxide (Cu-doped ZnO) nanoparticles using tobacco stem (TS) extract. The environmentally friendly synthesis method ensures distinct features, high efficiency, and applicability in various fields, particularly in solar cell technology and photocatalytic applications. ZnO nanostructures are investigated due to their unique properties, cost-effectiveness, and broad range of applications. The nanoparticles are synthesized with varying Cu concentrations, and their structural, morphological, and compositional characteristics are thoroughly analyzed. The Cu-doped ZnO nanoparticles exhibit improved properties, such as increased surface area and reduced particle size, attributed to the incorporation of Cu dopants. The green synthesis approach using TS extract serves as a stabilizing agent and avoids the toxicity associated with chemical methods. Characterization techniques including SEM, TEM, EDX, FTIR, and XRD confirm the successful synthesis of the nanoparticles. Photocatalytic degradation studies reveal that the 5% Cu-doped ZnO exhibits the highest photocatalytic activity against methylene blue, attributed to synergistic effects between Cu and ZnO, including oxygen vacancy and electron–hole pair recombination rate suppression. The photocatalytic mechanism involves the generation of superoxide and hydroxyl radicals, leading to methylene blue degradation. Furthermore, the Cu-doped ZnO nanoparticles demonstrate promising photovoltaic performance, with the optimal efficiency observed at a 5% Cu concentration. The study suggests that Cu-doped ZnO has the potential to enhance solar cell efficiency and could serve as an alternative material in solar cell applications. Future research should focus on refining Cu-doped ZnO for further improvements in solar energy conversion efficiency

3DOM Fe/Co-containing perovskites as bifunctional ORR/OER electrocatalysts for a photo-rechargeable zinc battery

Three-dimensionally ordered mesoporous perovskites (La0.8Ba0.2Fe1–xCoxO3–δ (x = 0, 0.2, 0.4)), which are integrated with a silicon photovoltaic cell are prepared. Their overall solar energy conversion and storage efficiency in zinc-ion-based batteries was assessed. The electrocatalytic activities were measured in OER/ORR, while the galvanostatic charge/discharge processes were applied to study battery performance under 1 sun irradiation. The electronic properties of the electrocatalysts were determined by X-ray absorption and UV photoelectron spectroscopies. The importance of controlling the oxidation state of cobalt ions to increase the specific capacity and energy density of the batteries was shown. The ORR activity depends on oxygen vacancies, inferred from the XANES and EXAFS spectra analysis. Their presence is associated with the Co2+/Co3+ ratio which controls the beneficial eg orbitals occupancy via the high spin d7 electron configuration. Herein, we report an overall energy conversion efficiency of 12.6 % for the PV-integrated La0.8Ba0.2Fe0.8Co0.2O3–δ photo-rechargeable battery cell.

Dual S-scheme MoS2/ZnIn2S4/Graphene quantum dots ternary heterojunctions for highly efficient photocatalytic hydrogen evolution

The layered chalcogenide ZnIn2S4 (ZIS) exhibits photo-stability and a tunable band gap but is limited in photocatalytic applications, such as hydrogen (H2) production, due to rapid carrier recombination and slow charge separation. To overcome these limitations, we have synthesized a ternary MoS2/ZIS/graphene quantum dots (GQDs) heterojunction, wherein MoS2 and GQDs are strategically attached to ZIS interlaced nanoflakes, enhancing light absorption across the 500–1500 nm range. This heterojunction benefits from dual S-scheme interfaces between MoS2-ZIS and ZIS-GQDs, establishing directed internal electric fields (IEFs). These IEFs accelerate the transfer of photoinduced electrons from the conduction bands of MoS2 and GQDs to the valence band of ZIS, promoting rapid recombination with holes and facilitating efficient catalytic reactions with plentiful photoinduced electrons stemmed from the conduction band of ZIS. As a result, the photocatalytic H2 production rate of the MoS2/ZIS/GQDs heterojunction is measured at 21.63 mmol h−1 g−1, marking an increase of 36.7 times over pure ZIS. This research provides valuable insights into designing novel heterojunctions for improved charge separation and transfer for solar energy conversion applications.

Elaboration, Structural and Optical Characterization of the New Ternary Chalcogenide SnSb<sub>2</sub>S<sub>5</sub>

In this study, -antimony sulfide (SnSb2S5) thin films with 200 nm, 312 nm, and 431 nm thicknesses were successfully fabricated using thermal evaporation. These films' structural, optical, and photoanode properties were meticulously characterized to assess their suitability for photovoltaic applications. X-ray diffraction (XRD) analysis confirmed the presence of an orthorhombic symmetry phase within the <em>Pnma</em> space group, ensuring the crystalline quality of the films. Raman spectroscopy further validated the crystal structure and provided detailed identification of the vibrational active modes specific to this pseudo-binary chalcogenide compound. Optical characterization revealed that the SnSb<sub>2</sub>S<sub>5</sub> thin films possess direct optical bandgap energies ranging from 1.91 to 1.99 eV, making them ideal for efficient light absorption in photovoltaic devices. The refractive index (n) displayed minimal variation within the absorption region, indicating stable optical properties. At the same time, it increased proportionally with film thickness outside the absorption region, suggesting enhanced optical behavior with thicker films. This characteristic is particularly advantageous for improving the efficiency of photoanode materials. The combination of favorable structural properties, optimal bandgap energies, and tunable optical responses positions SnSb<sub>2</sub>S<sub>5</sub> thin films as promising candidates for advanced photovoltaic and optoelectronic applications. These findings highlight the potential of SnSb<sub>2</sub>S<sub>5</sub> in developing high-performance photoanodes, contributing to the advancement of solar energy conversion technologies.

Efficient solar utilization: Multifunctional solar absorber devices realize self-driven hydrogen production

Considered as one of the effective approaches to address the energy crisis and develop green and sustainable energy, the application of solar energy in multiple stages was investigated in this study. By designing a WS2/ZnIn2S4 heterojunction, a multifunctional coupling system based on interfacial water evaporation technology was constructed. In this system, the water evaporation rate was 1.67 kgꞏm−2ꞏh−1, and the photocatalytic degradation efficiency of rhodamine B reached 96.5 %. Moreover, the electric energy output from thermoelectric conversion was innovatively in situ applied for photocatalytic hydrogen production, which increased the photocatalytic hydrogen production efficiency by five times, with a hydrogen production rate of 40.3 μmolꞏcm−2ꞏh−1. This study successfully integrated thermoelectric power generation, photocatalytic hydrogen production, and photocatalytic degradation of dye wastewater into an advanced solar-driven interface evaporation system, enabling the simultaneous conversion of solar energy into multiple forms of energy, improving solar energy utilization efficiency, which was of great significance for promoting the practical application of solar energy.

II-Scheme Heterojunction Frameworks Based on Covalent Organic Frameworks and HKUST-1 for Boosting Photocatalytic Hydrogen Evolution.

Covalent organic frameworks (COFs) are one type of promising polymer semiconductors in solar-driven hydrogen production, but majority of COFs-based photocatalytic systems show low photocatalytic efficiency owing to lack of metal active sites. Herein, we reported II-Scheme heterojunction frameworks based on COF (TpPa-1) and metal-organic framework (HKUST-1) for highly efficient hydrogen production. The coordination bonding directed self-assembly of HKUST-1 on the surface of TpPa-1 endows the heterojunction frameworks (HKUST-1/TpPa-1) with strong interface interaction, optimized electronic structures and abundant redox active sites, thus remarkably boosting photocatalytic hydrogen evolution. The hydrogen evolution rate for optimal HKUST-1/TpPa-1 is as high as 10.50 mmol g-1 h-1, which is significantly enhanced when compared with that of their physical mixture (4.13 mmol g-1 h-1), TpPa-1 (0.013 mmol g-1 h-1) and Pt-based counterpart (6.70 mmol g-1 h-1). This work offers a facile approach to the construction of noble-metal-free II-Scheme heterojunctions based on framework materials for efficient solar energy conversion.

Porous GaP/g‐C3N4 Photoanode for Enhanced Hydrogen Production

AbstractThe g‐C3N4 decorated porous gallium phosphide have been fabricated by a facile electrophoretic deposition (EPD) process. The morphology, element composition and light absorption of the GaP/g‐C3N4 photoanode were observed using field‐emission scanning electron microscopy, X‐ray photoelectron spectroscopy, ultraviolet and visible spectrophotometer, respectively. When acting as photoanode, porous GaP/g‐C3N4 serves as a direct Z‐scheme system, where photogenerated holes in GaP are expended by electrons generated from the g‐C3N4, inhibiting the corrosion of GaP. Therefore, the porous GaP/g‐C3N4 showed a larger photocurrent density, which is 2.1 times as large as that of the porous GaP without g‐C3N4, and a more stable photocurrent density for over 10000 s (at 0 V vs RHE). Thus, this work delivers a practical way to improve the photoelectrochemical stability and property of III–V semiconductor materials, which could be used in solar energy conversion fields.

A Survey on the Integration of Solar Photovoltaic Energy Conversion Systems into Commercial and Industrial Electrical Energy Usage

A Survey on the Integration of Solar Photovoltaic Energy Conversion Systems into Commercial and Industrial Electrical Energy Usage