Direct Conversion Of Solar Energy Research Articles

Visible-Light-Driven Photocatalytic H2 Production Using Composites of Co-Al Layered Double Hydroxides and Graphene Derivatives.

The direct conversion of solar energy into chemical energy represents an enormous challenge for current science. One of the commonly proposed photocatalytic systems is composed of a photosensitizer (PS) and a catalyst, together with a sacrificial electron donor (ED) when only the reduction of protons to H2 is addressed. Layered double hydroxides (LDH) have emerged as effective catalysts. Herein, two Co-Al LDH and their composites with graphene oxide (GO) or graphene quantum dots (GQD) have been prepared by coprecipitation and urea hydrolysis, which determined their structure and so their catalytic performance, giving H2 productions between 1409 and 8643 μmol g-1 using a ruthenium complex as PS and triethanolamine as ED at 450 nm. The influence of different factors, including the integration of both components, on their catalytic behavior, has been studied. The proper arrangement between the particles of both components seems to be the determining factor for achieving a synergistic interaction between LDH and GO or GQD. The novel Co-Al LDH composite with intercalated GQD achieved an outstanding catalytic efficiency (8643 μmol H2 g-1) and exhibited excellent reusability after 3 reaction cycles, thus representing an optimal integration between graphene materials and Co-Al LDH for visible light driven H2 photocatalytic production.

Photo-rechargeable asymmetric supercapacitors based on nickel–cobalt sulfide on titania as novel photo-active electrodes

Photo-supercapacitors (PSCs), which are environmentally benign devices for direct conversion and storage of solar energy into electricity, have a high potential for eliminating the requirement for grid electricity for a sustainable future. In this research, nickel sulfide (NS), cobalt sulfide (CS) and nickel cobalt sulfide (NCS) deposited on TiO2 nanotubes (TNT) have been prepared as novel photoactive electrodes for photorechargeable supercapacitors. X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Ultraviolet–visible spectroscopy (UV–Vis) were used to characterize the phase, morphology, elemental composition, oxidation states and optical properties of the films produced. Based on the photoelectrochemical measurements, the NCS@TNT-1 samples showed higher capability to produce and separate photogenerated charges compared to bare TNTs, NS@TNT and CS@TNT. The highest capacity of up to 471.6 mF/cm2 (at 0.7 mA/cm2) was shown by the NCS@TNT-1 electrode, which is about 11 times higher than that of bare TNTs (44 mF/cm2). In addition, the specific capacitance of the NCS@TNT-1 electrode (as the best sample) increased approximately twofold, reaching 955.6 mF/cm2 upon light illumination. Three photochargeable asymmetric supercapacitors were fabricated with NCS@TNT as the electrode and PVA-KOH as the electrolyte and separator. The specific capacitance of the fabricated supercapacitor increased by 1.57 times when illuminated by light. The device showed outstanding stability over 10,000 galvanostatic charge and discharge cycles with a capacity retention of 87 % and 94 % in the dark and under light conditions, respectively. More importantly, the illumination resulted in an extended discharge time.

Direct solar energy conversion on zinc–air battery

A concept of solar energy convertible zinc-air battery (SZAB) is demonstrated through rational design of an electrode coupled with multifunction. The multifunctional electrode is fabricated using nitrogen-substituted graphdiyne (N-GDY) with large π-conjugated carbonous network, which can work as photoresponsive bifunctional electrocatalyst, enabling a sunlight-promoted process through efficient injection of photoelectrons into the conduction band of N-GDY. SZAB enables direct conversion and storage of solar energy during the charging process. Such a battery exhibits a lowered charge voltage under illumination, corresponding to a high energy efficiency of 90.4% and electric energy saving of 30.3%. The battery can display a power conversion efficiency as high as 1.02%. Density functional theory calculations reveal that the photopromoted oxygen evolution reaction kinetics originates from the transition from the alkyne bonds to double bonds caused by the transfer of excited electrons, which changes the position of highest occupied molecular orbital and lowest unoccupied molecular orbital, thus greatly promoting the formation of intermediates to the conversion process. Our findings provide conceptual and experimental confirmation that batteries are charged directly from solar energy without the external solar cells, providing a way to manufacture future energy devices.

Photoelectrochemical, all-soluble iron redox-flow battery for the direct conversion of solar energy

A photoelectrochemical redox-flow battery (RFB) employing an all-soluble, aqueous coordination chemistry of the element iron is developed. The system is based on the ferro/ferricyanide redox couple as posolyte, the iron-triethanolamine (TEOA) complex as negolyte and a Ge/GaAs/GaInP triple-junction solar cell (TJSC) as power source. Combining a discharging flow-cell with the photoelectrochemical unit, we enable an operando monitoring of degradation phenomena at the working electrode similar to a rotating ring-disc electrode (RRDE). In this manner, an irreversible deactivation of an unprotected TJSC is observed after 15 h of operation. In a post-mortem SEM/EDX analysis, this performance loss is identified to result from a dissolution of the top junctions of the photoabsorber. Mitigating this corrosion is achieved by introducing a 150 nm thick protection layer of TiO2 via reactive sputtering. In this manner, a stable performance for more than 120 h is obtained. In view of the fact that the iron species selected for this study are affordable, abundant, water-based and non-toxic our device is a prototype of a green photoelectrochemical RFB at laboratory scale.

Mathematical analysis of the solar assisted thermoelectric generator

The direct conversion of solar energy into electrical energy is primarily dependent on the photovoltaic systems. However, in the last few decades, researchers have shown interest to work on the thermoelectric modules for direct conversion of solar thermal energy into electrical energy based on the Seebeck effect. This research paper provides a comprehensive analysis of various Solar Thermoelectric Generator (STEG) designs, focusing on their conversion efficiencies. Despite the comparatively lower efficiency of STEG in comparison to photovoltaic (PV) cells, owing to limitations in the figure of merit value and temperature differences between hot and cold sides of the thermoelectric modules, this study proposes strategies for enhancement. Approaches include the development of materials with higher figure of merit values, design optimization, solar tracking, heat storage systems, and efficient heat sink designs. Also, Mathematical analysis of the power and efficiency calculation of a STEG has been presented on the basis of some fundamental and derived mathematical equations. The overall efficiency of STEG, a product of Opto-thermal Efficiency and thermoelectric module efficiency, is explored, identifying an optimal hot side temperature for maximum efficiency. Module mismatch analyses for series and parallel connections are also derived, underscoring conditions for mitigating power loss. These findings serve as guidelines for designing more feasible and efficient STEG systems, with considerations for economic viability, sustainability and greenhouse gas reduction throughout the life cycle.

Exactly regulated copper catalysts exploiting isolated photoelectrochemical reduction of cuprous oxides and random mesh-structured TiO2 for enhanced photoelectrochemical CO2 conversion

Photoelectrochemical (PEC) CO2 reduction for the direct conversion of solar energy into carbon-based chemical fuels has received considerable attention owing to it being an inherently sustainable and green process. However,...

Mathematical approaches to a method of semiconductor materials films synthesis type AiiBvi for photosensitive structures used in alternative energy

The scientific direction of the synthesis of CdS and CdSe thin films by the method of chemical surface deposition (CSD) using aqueous solutions of cadmium-containing salts: chloride, nitrate, sulfate, acetate, iodide has been developed. A mathematical model of the CSD process of CdS and CdSe thin films was developed to improve the efficiency of experiments and reduce costs. The model makes it possible to determine the concentration of reagents, the duration, and the CSD temperature, which are necessary to obtain films of a specified thickness. The optimization of chemical deposition parameters of film-type semiconductor materials has been carried out. Based on the mathematical model, the optimal synthesis conditions were the next: concentration of cadmium-source salt - 0.01 mol/L, chalcogenizer - 1.0 mol/L or 0.1 mol/L in the chase of thiourea or sodium selenosulfate, respectively; temperature - 70?C and duration of 3 min. The mathematical dependence of the experimental studies results of the metal ions content in thin-film solar cells for the effective direct conversion of solar radiation into electrical energy taking into account errors was proposed.

A multimodal flow reactor for photocatalysis under atmospheric conditions.

Photocatalysis is a promising concept for the direct conversion of solar energy into fuels and chemicals. The design, experimental protocol, and performance of a multimodal and versatile flow reactor for the characterization of powdered and immobilized photocatalysts are herein presented. Ultimately, this instrument enables rigorous evaluation of photocatalysis performance metrics. The apparatus quantifies transient gas-phase reaction products via online real-time gas analyzer mass spectrometry (RTGA-MS). For H2, the most challenging gas, the photocatalytic system's RTGA-MS gas detection sensitivity spans over three orders of magnitude and can detect down to tens of parts per million under atmospheric conditions. Using Pt nanoparticles supported on anatase TiO2 photocatalyst via wet impregnation, the instrument's capability for the characterization of photocatalytic H2 evolution is demonstrated, resulting in an apparent quantum yield (AQY) of 48.1% ± 0.9% at 320nm, 45.7% ± 0.3% at 340nm and 31% ± 1% at 360nm. The photodeposition of Pt on anatase TiO2 was employed to demonstrate the instrument's capability to track the transient behavior of photocatalysts, resulting in an improved 55% ± 2% AQY for H2 evolution at 340nm from aqueous methanol. This photocatalytic instrument enables systematic study of a wide variety of photocatalytic reactions such as water splitting and CO2 reduction to valuable C2+ fuels and chemicals.

Advanced Interface Engineering in Gradient Core/Shell Quantum Dots Enables Efficient Photoelectrochemical Hydrogen Evolution.

Semiconductor core/shell quantum dots (QDs) are considered promising building blocks to fabricate photoelectrochemical (PEC) cells for the direct conversion of solar energy into hydrogen (H2 ). However, the lattice mismatch between core and shell in such QDs results in undesirable defects and severe carrier recombination, limiting photo-induced carrier separation/transfer and solar-to-fuel conversion efficiency. Here, an interface engineering approach is explored to minimize the core-shell lattice mismatch in CdS/CdSex S1-x (x = 0.09-1) core/shell QDs (g-CSG). As a proof-of-concept, PEC cells based on g-CSG QDs yield a remarkable photocurrent density of 13.1mAcm-2 under AM 1.5 G one-sun illumination (100mWcm-2 ), which is ≈54.1% and ≈33.7% higher compared to that in CdS/CdSe0.5 S0.5 (g-CSA) and CdS/CdSe QDs (g-CS), respectively. Theoretical calculations and carrier dynamics confirm more efficient carrier separation and charge transfer rate in g-CSG QDs with respect to g-CSA and g-CS QDs. These results are attributed to the minimization of the core-shell lattice mismatch by the cascade gradient shell in g-CSG QDs, which modifies carrier confinement potential and reduces interfacial defects. This work provides fundamental insights into the interface engineering of core/shell QDs and may open up new avenues to boost the performance of PEC cells for H2 evolution and other QDs-based optoelectronic devices.

Hydrogen Evolution of a Unique DNAzyme Composed of Cobalt-Protoporphyrin IX and G-Quadruplex DNA.

Molecular hydrogen (H2 ) is a clean and renewable fuel that has garnered significant interest in the search for alternatives to fossil fuels. Here, we constructed an artificial DNAzyme composed of cobalt-protoporphyrin IX (CoPP) and G-quadruplex DNA, possessing a unique H2 Oint ligand between the CoPP and G-quartet planes. We show for the first time that CoPP-DNAzyme catalyzes photo-induced H2 production under anaerobic conditions with a turnover number (TON) of 1229 ± 51 over 12 h at pH 6.05 and 10 °C. Compared with free-CoPP, complexation with G-quadruplex DNA resulted in a 4.7-fold increase in H2 production activity. The TON of the CoPP-DNAzyme revealed an optimal acid-base equilibrium with a pKa value of 7.60 ± 0.05, apparently originating from the equilibrium between Co(III)-H- and Co(I) states. Our results demonstrate that the H2 Oint ligand can augment and modulate the intrinsic catalytic activity of H2 production catalysts. These systems pave the way to using DNAzymes for H2 evolution in the direct conversion of solar energy to H2 from water.

Photoelectrochemical lithium extraction

The direct conversion of solar energy to valuable chemicals by mimicking the photosynthesis of natural leaves, known as artificial leaves, is promising for utilizing renewable energy. Herein, we demonstrate the successful extraction of lithium (Li) from natural brine using a photoelectrochemical (PEC) system, combined with a Li-selective membrane process. A Si photoelectrode, with three p–n junctions connected in series (3S-Si), was seamlessly embedded into an H-cell with two compartments separated by a Li1+xAlxGe2−x(PO4)3 membrane. The unassisted PEC Li extraction was performed under AM 1.5 G illumination without other external energy input. The Li concentration in the enriched solution reached 2924.96 ppm with 99.4 % atomic selectivity after two PEC stages, and the solar-to-Li extraction efficiency reached 0.355 %. Finally, we obtained the valuable product Li2CO3 with 99.93 % purity. Economic analysis revealed that this solar-driven Li extraction system was more profitable than the PEC systems for H2 generation, N2 and CO2 reduction. Our study offers a promising approach for Li mining using sustainable energy and improves the economic viability of Li extraction from natural brine.

Using Direct Solar Energy Conversion in Distillation via Evacuated Solar Tube with and without Nanomaterials

As is widely known, the issue of freshwater scarcity affects practically all people, and all are looking for innovative and workable ways to attempt to solve this issue. In this work, a novel method of desalination is proposed. The proposed system consists of a solar collector (PTSC), evacuated pipe (EP), condenser (CU), and separation unit (SU). The working principle of the system is heating the feed saline water using the PTSC and EP and controlling the water flow rate to control the output conditions of the EP. The produced vapor is therefore separated from salty water using the SU. In addition, the generated steam is condensed into the CU to produce a freshwater distillate. Consequently, the effect of solar radiation on the affecting temperatures was tested. In addition, the effect of using different water flow rates (6, 7.5, 10, 20, 40, and 60 L/h) inside the EP on the system productivity was investigated. The primary findings of this work may be highlighted in relation to the experiments conducted. At midday, when ultraviolet irradiance reached its highest, the EP’s water flow entrance and outflow had the largest temperature differential. In addition, the lower the water flow rate inside the EP, the higher the water temperature, the higher the evaporation rate of the system, and the greater the freshwater productivity of the system. At 6 L/h, the water’s highest temperature was 92 °C. Moreover, the best performance of the system was obtained at 7.5 L/h, where the freshwater production and average daily effectiveness of the distillate process were 44.7 L/daytime and 59.6%, respectively. As well, the productivity of EP was augmented by around 11.86% when using graphite nanoparticles. Additionally, the distilled freshwater from the system operating at the flow rate of 7.5 L/h costs 0.0085 $/L.

2D Fluid Modeling of Light Pumped Na Containing Plasma to Develop a Prototype of a Photo Electromotive Force Converter

The development of innovative technologies for direct solar energy conversion is one of the main trends of modernity. The use of solar semiconductor panels is well-known in solar photovoltaics. As an alternative to this, the use of gas photoplasma can be promising. However, research in this direction is still very fragmentary so far. This paper shows the results of a systematic study of photoplasma in mixtures of sodium and inert gases to obtain photo-EMF in a gas cell. A fluid modeling considering detailed plasma chemistry, radiation transfer, and charge diffusion processes and 2D simulation were fulfilled and main plasma parameters were obtained and analyzed. In particular, non-trivial dependence of EMF in a two-chamber gas cell containing sodium and argon on the pressure of the inert gas was obtained, reaching up to 1.3 eV by absolute value at 100 Torr of Ar and changing its sign near 5 Torr at the decrease of the pressure.

A Novel Solar System of Electricity and Heat

Thermoelectric devices may have an essential role in the development of fuel-saving, environmentallyfriendly, and cost-effective energy sources for power generation based on the direct conversion of heat into electrical energy. A wide usage of thermoelectric energy systems already exhibits high reliability and long operation time in the space industry and gas pipe systems. The development and application of solar thermoelectric generators (TEGs) arelimited mainly by relatively low thermoelectric conversion efficiency. Forthe first time, we propose to use the direct energy conversion of solar energy by TEGs based on the high-performance multilayer thermoelectric modules with electric efficiency of ~15%. Solar energy was absorbed and converted to thermal energy, which is accumulated by a phase-change material (aluminum alloys at solidification temperature ~900 K). The heat flow from the accumulator through the thermoelectric convertor (generator) allows electrical power to be obtained and the exhaust energy to be used for household purposes (heating and hot water supply) or for the operation of a plant for thermal desalination of water.

Exploration of 1D-2D LaFeO3/RGO S-scheme heterojunction for photocatalytic water splitting

Sustainable energy innovation is spearheading the way to achieve decarbonisation through commercially viable and highly competitive renewable technologies for green hydrogen. Photocatalytic water splitting has received global attention, as it promotes the direct conversion of solar energy to chemical energy and hydrogen production. Lanthanum orthoferrite (LaFeO3) has been selected due to its narrow bandgap perovskite-oxides (ABO3) type nature, low cost and high chemical stability but it is limited with fast charge recombination. To circumvent its constraint of fast charge recombination, an efficient graphene-based nanocomposite has been prepared by employing reduced graphene oxide (RGO) nanosheets as charge separators for visible light driven photocatalytic water splitting. Here, we present a thorough physical and spectroscopic characterization of the Lanthanum orthoferrite/Reduced Graphene oxide (LaFeO3/RGO) nanocomposites, and investigate its photocatalytic and photoelectrochemical performance. The photocurrent density of the nanocomposites demonstrated ∼21 times higher in comparison to pure LaFeO3. The as-prepared nanocomposites have been successfully used as photocatalysts for H2 generation through water reduction under visible light. A significant enhancement in H2 generation has been recorded for nanocomposites (∼82 mmol g−1 h−1) as compared to that of bare LaFeO3 (∼9 mmol g−1 h−1) which is among the highest values obtained using noble-metal-free graphene-based photocatalytic nanocomposites. This work offers a facile approach for fabricating highly efficient 1D-2D heterostructure for photocatalysis application.

Effective charge transfer regulation for robust photoelectrochemical water splitting

The direct conversion of solar energy to chemical fuels is an important approach to address the world's challenges of sustainable energy, environmental and climate issues owing to the abundant solar energy. Photoectrochemical (PEC) cells as a promising technology by the utilization of solar energy have received much attention for the generation of renewable hydrogen from water splitting on a large scale. However, the efficiency of solar energy conversion into hydrogen is still limited by narrow light absorption, slow charge transfer and sluggish surface reaction kinetics. Great efforts in the regulation of charge transfer have been summarized toward efficient solar-to-chemical energy conversion in this review. Firstly, various photoanodes and photocathodes are been discussed. Then, different strategies such as morphological regulation, heteroatom and defect introduction, heterostructure engineering and cocatalyst incorporation are elaborated to accelerate the charge transfer process and optimize the PEC performance. Finally, the perspectives and comprehensive outlooks on the future regulation of charge transfer are also proposed. This review offers an overview for the rational design and development of the promising photoelectrodes and the delicate manipulation of photogenerated charge transfer in PEC systems for effective solar-to-chemical energy conversion.

Unravelling the interfacial water structure at the photocatalyst strontium titanate by sum frequency generation spectroscopy.

The direct conversion of solar energy to hydrogen is considered as a possible method to produce carbon neutral hydrogen fuel. The mechanism of photocatalytic water splitting involves the chemical breakdown of water and re-assembly into hydrogen and oxygen at the interface of a photocatalyst. The selection rules of a suitable material are well established, but the fundamental understanding of the mechanisms, occurring at the interface between the catalyst and the water, remains missing. Using surface specific sum frequency generation spectroscopy, we present here characterisation of the interface between water and the photocatalyst strontium titanate (SrTiO3). We monitor the OH-stretching vibrations present at the interface. Their variations of intensities and frequencies as functions of isotopic dilution, pH and salt concentration provide information about the nature of the hydrogen bonding environment. We observe the presence of water molecules that flip their orientation at pH 5 indicating the point of zero charge of the SrTiO3 layer. These water molecules are oriented with their hydrogen away from the surface when the pH of the solutions is below 5 and pointing towards the surface when the pH is higher than 5. Besides, water molecules donating a H-bond to probably surface TiOH groups are observed at all pH.

Emerging photo‐integrated rechargeable aqueous zinc‐ion batteries and capacitors toward direct solar energy conversion and storage

AbstractPhoto‐integrated rechargeable aqueous zinc‐ion batteries (ZIBs)/zinc‐ion capacitors (ZICs) have recently attracted substantial attention as a viable strategy to realize solar to electrochemical energy conversion and storage in a single device. Herein, a timely perspective on the latest advances in photo‐integrated rechargeable ZIBs/ZICs is presented. We first provide a brief introduction for the three different device types and working principles of the photo‐integrated rechargeable ZIB/ZIC devices, including tandem connected photo‐rechargeable hybrid energy systems, photo‐electrode integrated ZIBs, and photo‐rechargeable ZIBs/ZICs. Then, the significant advances in configuration design, materials chemistry, and performance evaluation of photo‐integrated rechargeable ZIBs/ZICs are systematically discussed. At last, the current challenges and future research emphases are suggested, which is to pave the way for the photo‐integrated rechargeable ZIBs/ZICs from laboratory technology to commercialization. This short yet informative perspective aims to evoke more research interests in developing high‐performance photo‐integrated rechargeable ZIBs/ZICs and other hybrid energy systems toward the direct conversion and storage of solar energy to electrochemical energy.

Marketing component of green technologies energy efficiency at traditional and renewable energy facilities

The article examines the economic aspects of the production of electrical engineering and electricity at traditional and renewable energy facilities. The authors emphasized that Ukraine has great potential for the development of wind and solar energy capacities, but the relatively high current price of such technologies compared to conservative sources of electricity generation makes new power generation capacities from RES twice as expensive. The authors consider, improving energy efficiency could significantly reduce the growth in energy consumption: according to the International Energy Agency, the implementation of measures to improve energy efficiency on a global scale by 2030 would lead to an increase in energy consumption by 40%, while failure to implement these measures would mean a 60% increase in demand. It is proved that in Ukraine the most promising direction is the use of solar energy. The authors focused on the direct conversion of wind and solar energy into direct current electrical energy. The possibility of converting wind and solar energy into thermal energy without preliminary concentration of the solar radiation flux for heating the coolant and subsequent supply to heating objects has been proved. It was noted that a significant modernization of power plants using renewable energy sources or the construction of additional capacities (for an amount exceeding 50% of their initial cost) after 2014, 2020 led to a reduction in the rates of the “green” tariff for the entire power plant by 10%, 20% respectively and will lead to 2024 by 30%.

Front Cover: Carbon Neutralization, Volume 2, Issue 1, January 2023

Front cover image: In article number 10.1002/cnl2.41, Yuxin Tang and coworkers provide a short perspective on photo-integrated rechargeable aqueous zinc-ion batteries (ZIBs)/zinc-ion capacitors (ZICs). Under light illumination, the integrated solar-charging modules can charge the ZIBs/ZICs, realizing direct solar energy conversion and storage. Such an integrated energy system demonstrates promising application potential in various fields such as large-scale energy storage, self-powered wearable electronics and internet of things.