Photocatalytic Reaction Process Research Articles

Effect of Surface Anions Adsorbed by Rutile TiO2 (001) on Photocatalytic Nitrogen Reduction Reaction: A Density Functional Theory Calculation

The adsorption of common anions found in water can have a considerable impact on the surface state and optical characteristics of titanium dioxide (TiO2), which has an important impact on the photocatalytic nitrogen reduction reaction (NRR). This work utilizes density functional theory (DFT) computations to examine the electronic and optical characteristics of the TiO2 (001) surface under various anion adsorptions in order to clarify their influence on the photocatalytic NRR of TiO2. The modifications in the structure, optical, and electronic properties of TiO2 before and after anion adsorption are investigated. In addition, the routes of Gibbs free energy for the NRR are also evaluated. The results indicate that the adsorption of anions modifies the surface characteristics of TiO2 to a certain degree, hence impacting the separating and recombining charge carriers by affecting the energy gap of TiO2. More importantly, the adsorption of anions can increase the energy barriers for the NRR, thereby exerting a detrimental effect on its photocatalytic activity. These findings provide a valuable theoretical contribution to understanding the photocatalytic reaction process of TiO2 and its potential application of NRR in the actual complex water phase.

CeO2 nanoparticle-modified BiOI nanoflowers as visible-light-driven heterojunction photocatalyst for tetracycline degradation and antibacterial

BiOI, a typical narrow-band gap visible-light-driven photocatalyst, possesses a high recombination rate of photogenerated electrons and holes, which hinders its practical application in environmental remediation. To improve its photocatalytic efficiency, BiOI/CeO2 heterojunction was designed and prepared via a facile chemical bath method. Compared to pure BiOI, the BiOI/CeO2 heterojunction not only enhanced the absorption of visible-light but also improved the separation and transfer efficiency of photogenerated carriers. Impressively, the BiOI/CeO2 heterojunction with a BiOI:CeO2 molar ratio of 2:1 (named CBOI-2) exhibited the best photocatalytic performance. The CBOI-2 heterojunction can degrade 80 % of tetracycline within 60 min, and the degradation activity was almost intact after three cycles. The reaction rate constant of CBOI-2 heterojunction was 22.1 times that of BiOI and 5.8 times that of CeO2. Moreover, CBOI-2 heterojunction behaves much better in antibacterial effect whose antibacterial efficiency reaches ∼99.6 %. A double charge-transfer mechanism was proposed in this work and it indicated that the improved photocatalytic efficiency mainly resulted from an enhanced separation and transfer of photogenerated carriers. During the photocatalytic reaction process, superoxide radicals, hydroxyl radicals and holes were generated, which play important roles in the degradation of tetracycline and antibacterial. This work provides important insights into the design of visible-light-driven photocatalysts with high photocatalytic activity for antibiotic degradation and bacteria killing.

Construction of a Bi2S3/Bi0.5Na0.5TiO3 Composite Catalyst with S Vacancies for Efficient Piezo-Photocatalytic Hydrogen Production.

Photocatalytic hydrogen production with low environmental and economic costs is expected to be a powerful means to alleviate energy and environmental problems. However, how to inhibit the rapid recombination of photogenerated carriers is a challenge that photocatalytic hydrogen production has to face. In this study, the coupling of the piezoelectric effect and vacancy engineering into the photocatalytic reaction process synergistically promoted carrier separation, thereby promoting the improvement of hydrogen production performance. Specifically, the novel dual piezoelectric Bi2S3/Bi0.5Na0.5TiO3 (BS-12/BNT) piezo-photocatalyst rich in S vacancies was synthesized by an impregnation method. The hydrogen generation rate of 5% BS-12/BNT under the combined impact of light and ultrasound was up to 1019.39 μmol/g/h, which is 9.5 times higher than that of pure BNT. Various characterization analyses have confirmed that the piezoelectric-photocatalytic activity of BS/BNT composite materials is significantly improved, mainly due to the introduction of S vacancies and piezoelectric fields, which enhance the absorption of sunlight, reduce interface resistance, and so raise the photogenerated carriers' separation efficiency. In addition, the stability of BS/BNT is significantly better than that of the previously synthesized catalysts. Finally, according to the results of XPS, UV-vis, and ESR, the active groups and possible electron transfer paths generated during the piezoelectric-photocatalytic hydrogen production process were studied. This work presents a new approach to promote hydrogen production performance through the synergistic effect of the piezoelectric effect and S vacancies.

Enhanced photocatalytic removal of NOx through the synergistic effect of photothermal activation and bipyroelectricity

Photocatalysis provides a green and promising strategy for removing nitrogen oxides (NOx), one of the main pollutants in the atmosphere. However, few studies have been able to utilize the infrared portion of sunlight due to its low energy, which accounts for >50% of the total sunlight. The conversion of infrared light into heat is an effective but flawed approach for photocatalysis, because high temperature cannot only reduce the activation barrier of the reaction and improve the migration rate of charge carriers, but also increase the collision probability of photogenerated carriers. Here, C/PVDF-BaTiO3 (polyvinylidene fluoride, PVDF) photocatalytic films with bi-pyroelectric effect are designed to boost the full-spectrum solar photocatalytic conversion of NOx. During the photocatalytic reaction process, the photothermal conversion of carbon and the dual pyroelectricity synergistically enhance and reinforce each other’s effects. The 0.5 wt% C/PVDF-BaTiO3 film achieves a denitrification efficiency of 60% in a flow reaction, surpassing both the BaTiO3 and PVDF-BaTiO3 samples by 25% and 15% respectively.

Small Conjugated Organic Ligand-Modified Polyoxometalate-Based Hybrid Materials for Boosting Photocatalytic CO2 Reduction.

Photocatalytic carbon dioxide (CO2) reduction to value-added chemicals is a multielectron transfer process, and the crucial step is the synthesis of photocatalysts. The introduction of small conjugated organic ligands can make the catalytic active site of the compound easier to be exposed in the reaction system and fully contact with the substrate, accelerating the photocatalytic reaction process. In this paper, we synthesized two isomorphic compounds, namely, {[Co(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (1) and {[Ni(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (2) (mtrz = 1-methyl-1,2,4-triazole). We found that compound 1 has a great photocatalytic performance through a series of experiments, with a CO reduction yield of 7364.92 μmol g-1 h-1 and a CO selectivity of 82.5%. Furthermore, the high catalytic activity can be maintained over four cycle experiments. The catalytic mechanism of its photocatalytic system is also elucidated, which provides an idea for realizing efficient catalytic reduction of CO2 to CO.

Construction of a BiOCl/Bi2O2CO3 S-Scheme Heterojunction Photocatalyst via Sharing [Bi2O2]2+ Slabs with Enhanced Photocatalytic H2O2 Production Performance.

The construction of a close contact interface is key to enhancing the photocatalytic activity in heterojunctions. In the work, the BiOCl/Bi2O2CO3 of sharing [Bi2O2]2+ slabs S-scheme heterojunction was prepared by a HCl in situ etching method. The optimal composite photocatalyst could accomplish sizable productivity of H2O2 to 2562.95 μmol g-1 h-1 under simulated solar irradiation, higher than that of primitive Bi2O2CO3 and BiOCl. Moreover, the synthesized catalysts showed good stability. The band structures of BiOCl and Bi2O2CO3 were determined, confirming the formation of BiOCl/Bi2O2CO3 S-scheme heterojunction The BiOCl/Bi2O2CO3, which obviously improved the separation efficiency of photoinduced carriers and effectively enhanced the redox ability of the photocatalyst. In addition, density functional theory (DFT) calculations were utilized to analyze the electron transfer properties and the constitution of the built-in electric field at the interface of BiOCl and Bi2O2CO3. The photocatalytic reaction process was further researched by electron paramagnetic resonance (EPR), indicating the active species in the photocatalytic production of hydrogen peroxide. Eventually, a feasible S-scheme electron transfer mechanism on the BiOCl/Bi2O2CO3 heterojunction during the photocatalytic H2O2 production process was proposed and discussed. This work provides a reliable strategy for the fine design of the S-scheme heterojunction.

Efficient and selective H2O2 production through uranyl-assisted photocatalytic oxygen reduction reaction process in a uranium-organic framework

Efficient and selective H2O2 production through uranyl-assisted photocatalytic oxygen reduction reaction process in a uranium-organic framework

CoS nanoparticles anchored on g-C3N4 via a facile and green strategy for boosting visible-light-driven photocatalytic hydrogen production

Boosting the photo-induced charge separation on the interface of semiconductor photocatalyst still is an enduring challenge in photocatalytic water splitting for hydrogen production. Herein, 0D/2D CoS/g-C3N4 heterostucture was designed and constructed via a facile and green solvothermal synthesis, wherein the CoS nanoparticles were dispersedly anchored on the surface of g-C3N4 nanosheets. The morphology, microstructure, component of g-C3N4 and CoS/g-C3N4 samples were detailedly characterized by a sequence of physical and chemical characterizations. The thus-designed CoS/g-C3N4 photocatalysts manifest the enhanced photocatalytic performance for hydrogen production relative to the pristine g-C3N4. The optimized CoS/g-C3N4 photocatalyst gives the H2 production rate of 532 μmol g−1 h−1, which is about 44 times higher than that of the pristine g-C3N4. The photoelectrochemical measurements prove that its promotion is mainly attributed to the reinforced interface charge separation and transfer and the lower overpotential. Furthermore, the photoluminescence decay data of g-C3N4 and CoS/g-C3N4 photocatalysts clearly demonstrates the crucial role of CoS cocatalyst, which can prolong the charge lifetime of photocatalyst benefiting to the photocatalytic reaction process. This work provides a promising counterpart to realize the interface charge separation and transport in heterogeneous photocatalysis.

Revealing electron numbers-binding energy relationships in heterojunctions via in-situ irradiated XPS

Photogenerated charge transfer from photocatalysts to surface sites is a crucial step in guaranteeing photocatalytic efficiency, however, comprehending this process remains a challenge. While in-situ irradiated XPS (ISI-XPS) can function as a powerful method to investigate the electron transfer route and briefly determine the electron quantity under simulated photocatalytic conditions, the precise amount of transferred photogenerated electrons is still unknown. Based on an oxygen-doped ZnIn2S4 nanosheet on carbon nanofibers heterostructure catalysis, we discovered a potential means of calculating the precise quantity of photogenerated electrons through ISI-XPS. Additionally, we further propose a parameter to describe how many photogenerated electrons can participate in the photocatalytic reaction in conjunction with performance under monochromatic light and the corresponding electron count. Concurrently, the oxygen dopants serve as active sites to enhance the photocatalytic reaction process. This study presents a fresh outlook on the utilization of ISI-XPS and imparts a more profound understanding of the mechanism.

Solar-driven Bi6O5(OH)3(NO3)5(H2O)3/Bi2WO6 heterojunction for efficient degradation of organic pollutants: Insights into adsorption mechanism, charge transfer and degradation pathway

Actualizing controllable construction of efficient heterojunction nanocomposites remains a challenge in the field of photocatalytic water remediation, which can be got over through exploiting in-situ attachment approaches between different semiconductors. Based on this, we successfully fabricated a unique separable Z-scheme Bi6O5(OH)3(NO3)5(H2O)3/Bi2WO6 (BON/BW) nanoflowers by an in-situ growth strategy. The profitable photogenerated carriers transfer mediated by Z-scheme heterojunction greatly accelerated the generation of •O2– and •OH. The strong adsorption of 4-nitrophenols (4-NP) with parallel configuration on side Bi2WO6 in BON/BW nanocomposites also provides great convenience for subsequent degradation steps. By optimizing multiple steps in the photocatalytic reaction process, BON/BW showed far superior photodegradation performance compared to single components. The causes and consequences of 4-NP photodegradation were explored through LC-MS tests, theoretical calculations, and toxicity analysis, and a green and safe degradation pathway was proposed. More experiments have confirmed that the synthesized BON/BW composites also have excellent degradation ability against other pollutants under sunlight, demonstrating excellent universality. With any luck, the logical design of heterojunction photocatalysts for effective photocatalytic water remediation should be aided by this study.

Hierarchically, Low Band Gap Nanohybrid InVO4-CdS Heterojunction for Visible Light-Driven Toxic Organic Dye Degradations.

The synthesis of InVO4-CdS heterojunction photocatalysts has been achieved by a novel two-step approach, including a microwave-assisted technique, followed by a moderate hydrothermal method, marking the first successful instance of such a synthesis. X-ray diffraction, field-emission scanning electron microscopy, elemental color mapping, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, Raman analysis, photoluminescence, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller were employed to investigate the crystal structures, surface morphologies and particle sizes, chemical compositions, and optical characteristics of the as-synthesized materials. The research results indicated that the heterojunction InVO4-CdS, as synthesized, consisted of InVO4 microrods with an average size of around 15 nm and cadmium sulfide (CdS) microflowers with a diameter of 1.5 μm. Furthermore, all of the heterojunctions had favorable photoabsorption properties throughout the visible-light spectrum. The photocatalytic efficiency of the samples obtained was thoroughly assessed by the degradation of acid violet 7 (AV 7) under visible light irradiation with a wavelength greater than 420 nm. The photocatalytic efficiency for the decomposition of AV 7 was greatly enhanced in the InVO4-CdS (IVCS) heterojunctions when compared to prepared bare InVO4 and CdS. Additionally, it was observed that the composite material consisting of IVCS 3 wt % InVO4 combined with CdS exhibited the most significant enhancement in catalytic effectiveness for the photodegradation of AV 7 dye. Specifically, the catalytic performance of this composite material was found to be around 69.4 and 76.2 times greater than that of pure InVO4 and CdS, respectively. Furthermore, the experimental procedure including active species trapping provided evidence that h+ and •O2- radicals were the primary active species involved in the photocatalytic reaction process. Additionally, a potential explanation for the improved photocatalytic activity of the InVO4-CdS heterojunction was presented, taking into account the determination of band positions.

Two 2D Metal-Organic Frameworks Based on Purine Carboxylic Acid Ligands for Photocatalytic Oxidation of Sulfides and CO2 Chemical Fixation.

Two two-dimensional (2D) layered metal-organic frameworks (MOFs), namely, {[Yb(L)(H2O)2NO3]·2H2O}n (Yb-MOF) and [Er(L)(H2O)3Cl]n (Er-MOF) (H2L = 5-((6H-purin-6-yl)amino)isophthalic acid), were constructed by a solvothermal method and characterized. The catalytic performance study showed that the Yb-MOF could efficiently catalyze the oxidation of sulfides to sulfoxides under 15 W light-emitting diode (LED) blue light irradiation. Electron paramagnetic resonance spectroscopy and free-radical trapping experiments demonstrated that the photocatalytic reaction process involved •O2-, and the corresponding mechanism was proposed. Moreover, Er-MOF exhibited good catalytic efficiency and excellent substrate tolerance in the cycloaddition reaction of CO2, and the reaction conditions were mild. After 5 cycles, the catalytic activities of two MOFs did not significantly decrease, and the framework structures remained unchanged. Therefore, the Yb-MOF and Er-MOF were considered efficient and stable heterogeneous catalysts.

Regulation of d-band center of TiO2 through fluoride doping for enhancing photocatalytic H2O2 production activity

Titanium dioxide (TiO2) has received extensive attention for photocatalytic hydrogen peroxide (H2O2) production, with the d-band center related to the adsorption performance, which affects the photocatalytic reaction process. Herein, an ingenious strategy to lower the antibonding-orbital occupancy in the Ti 3d orbital by fluoride ion (F−) doping is proposed, with density functional theory calculations predicting that F-doping into TiO2 induces a non-uniform charge distribution and enables an upshift of the d-band center in F/TiO2. This manipulation provides accessible active centers with favorable d-band energy levels, which can improve the charge-transfer behavior, strengthen the interaction between the adsorbed oxygen and the photocatalyst, and reduce the adsorption energy of oxygen, eventually promoting the photocatalytic H2O2 production rate. The experimental results further confirm that a lower antibonding-orbital occupancy can intensify the adsorption of atomic oxygen at the Ti sites. Electron paramagnetic resonance experiment reveals that the presence of F− ions in the lattice induces the formation of Ti3+ centers that localize the extra electron needed for charge compensation. Femtosecond transient absorption (fs-TA) spectroscopy suggests that photogenerated electrons are transferred from the conduction band of F/TiO2 to the Ti3+ surface states and surface F− ions, expediting the separation of electrons and holes. Consequently, with F− doping in TiO2, the photocatalytic H2O2 production yields improved from 277 to 467 μmol·g−1·h−1, with ethanol as a sacrificial reagent. This study provides a new strategy for regulating the d-band center to optimize the adsorption strength between the photocatalyst and oxygen atoms and achieve enhanced photocatalytic H2O2 production performance.

Preparation of S-C3N4/AgCdS Z-Scheme Heterojunction Photocatalyst and Its Effectively Improved Photocatalytic Performance.

In this study, S-doped graphitic carbon nitride (S-C3N4) was prepared using the high-temperature polymerization method, and then S-C3N4/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on the surface of S-C3N4. Experimental results show that the AgCdS NPs were evenly dispersed on the surface of S-C3N4, indicating that a good heterojunction structure was formed. Compared to S-C3N4, CdS, AgCdS and S-C3N4/CdS, the photocatalytic performance of S-C3N4/AgCdS has been significantly improved, and exhibits excellent photocatalytic degradation performance of Rhodamine B and methyl orange. The doping of Ag in collaboration with the construction of a Z-scheme heterojunction system promoted the effective separation and transport of the photogenerated carriers in S-C3N4/AgCdS, significantly accelerated its photocatalytic reaction process, and thus improved its photocatalytic performance.

Cobalt and chlorine co-doped Bi5O7I catalysts for LED-induced photocatalytic or PMS-activation antibiotics degradation

Multifunctional semiconductor catalysts can meet the urgent needs for the removal of antibiotic pollutants in water. Bifunctional catalysts, cobalt and chlorine co-doped Bi5O7I (signed as Co-BIC) catalysts, were purposefully designed through a two-step aqueous strategy. The preformed Bi5O7I precursor provided one-dimensional structure and Bi-rich character for the construction of Co-BIC catalysts. Co and Cl co-doping in Bi5O7I crystals can form a doping energy level and improve the internal electric field, which led to enlarged visible-light absorption and charge separation efficiency during the photocatalytic reaction process. These advantages made Co-BIC crystals exhibit good photocatalytic activities for the removal of antibiotic levofloxacin (LEV), ciprofloxacin (CIP) and tetracycline (TC) under visible LED (100 W) light irradiation. The degradation efficiency of LEV, CIP and TC over the typical Co-BIC-60 catalyst can reach more than 80 % under 60 min of LED irradiation. In the system of Co-BIC activated peroxymonosulfate (PMS), ∼ 90 % of LEV, CIP and TC degraded within 20 min over 20 mg of Co-BIC-60 catalyst. The mechanism of photocatalytic degradation and PMS oxidation degradation over Co-BIC catalysts was proposed on band structures of Co-BIC catalysts and the active species in the capture experiments. This work could provide new ideas for the preparation of bismuth oxyhalide catalysts coupled with transition metal elements.

Improving Photocatalytic Performance through Incorporation of Various Cations in A-site of Double Perovskite Material (Cs0.50MA0.50)2SnI6 for Degradation of Methylene Blue Dye Pollutant under Visible Light Irradiation

In this article, undoped double perovskite materials like caesium tin iodide (Cs2SnI6), methyl ammonium tin iodide [MA2SnI6: MA denotes CH3NH3+] and mixed double perovskite material [(Cs0.50MA0.50)2SnI6] were synthesized using a wet chemical methodology. The crystal structure confirmation, optical properties, thermal properties, surface morphology and presence of elemental composition of the prepared samples using XRD, UV, TGA and FESEM-EDAX analyses were thoroughly investigated. The synthesized materials were employed as photocatalysts to degrade methylene blue dye within 120 min under visible light. An increase in the optical properties of the synthesized double perovskite materials was confirmed by ultraviolet (UV) analysis, which showed that the introduction of various cations into the perovskite material at the A-site shifted the photoluminescence (PL) emission peak to the red. TGA results demonstrated that (Cs0.50MA0.50)2SnI6 has greater thermal stability, which was confirmed by the presence of 43% of sample despite the temperature reaching almost 870 ºC. Doped double perovskite material (Cs0.50MA0.50)2SnI6 exhibited increased photocatalytic activity, with methylene blue dye degradation efficiency attaining 89% after 120 min of visible light irradiation, which is greater than pure double perovskite materials. The photocatalytic degradation of methylene blue dye is mostly facilitated by hydroxyl radicals and holes, according to a radical trapping experiment that we conducted by employing different scavengers. The results of the current work showed that doped double perovskite materials [(Cs0.50MA0.50)2SnI6] exhibit high thermal stability as well as higher photocatalytic activity than pure double perovskite materials. A possible photocatalytic reaction process is also diagrammatically using the band positions of double perovskite materials found using Mott-Schottky plots , which confirms that the synthesized double perovskite material has an N-type semiconductor nature.

An overview of prominent factors influencing the photocatalytic degradation of cationic crystal violet dye employing diverse nanostructured materials

AbstractCrystal violet (CV), a cationic dye, has been demonstrated to be a powerful carcinogen, a mitotic toxin and poisonous to mammalian cells such that the predominant presence of the dye invariably causes several effects of destruction to mankind and it necessitates a clarion call to do away with this nuisance before it can produce a snowball effect. The recent widespread reporting of the photocatalysis‐mediated degradation of CV as an emerging technique for removing this dangerous dye from aqueous mediums highlights its effectiveness. Numerous researchers have contributed substantially to describing how photocatalysis‐based nanomaterials could be used to degrade CV. The fundamentals and the factors that predominantly influence CV degradation are highlighted in this work. These factors include the nature of nanomaterials, catalyst concentration, dye dosage, pH of the solution in use, temperature and light intensity. Additionally, thorough kinetics and mechanistic descriptions are also included to give crucial insights into the light‐mediated reaction of CV. The present study's findings have the potential to alleviate practitioners and researchers of the burden of having to navigate through numerous studies under each category of parameters to get an exhaustive overview of all of the different variables that may affect the photocatalytic degradation of CV dye. In order to further enhance the photocatalytic degradation efficiency of CV, researchers can expand on this study by investigating novel strategies to lessen the impact of certain elements that adversely affect the photocatalytic reaction process. The potential prospects for extending the advancement of scientific study in this area are also explored. © 2024 Society of Chemical Industry (SCI).

Iron-Based nanoporous Metal-Organic frameworks with Side-Chain amino substituents for Efficiency-Regulated oxygen evolution reaction

Nanoporous iron-based MOFs, possessing notable attributes such as adjustable structure, considerable porosity, and large surface area, exhibit considerable promise for various applications in the field of photocatalysis. However, the effect of the ligand substitution ratio on the photocatalytic reaction process is currently unknown. In the current investigation, a series of iron-based MOFs MIL-101(Fe)-X with various ratios of amino substituents (X = H: NH2 = 1:0, 1:0.5, 1:1, 1:2, 1:4, 0:1) were synthesized using the solvothermal method. The morphology and structure were characterized using SEM, TEM, XRD, XPS, BET, FT-IR, etc. Their efficacy as water oxidation catalysts under AM1.5G (solar light) irradiation was investigated. The findings of the study indicated that MIL-101(Fe) with an X value of 1:2 exhibited the highest surface area of 380.4 m2/g. This resulted in the exposure of a greater number of active sites, leading to enhanced charge separation efficiency and exceptional oxygen evolution activity when illuminated by simulated sunlight. The oxygen evolution rate under solar light was measured to be 11.7 mmol·h−1·g−1. This research confirmed the effect of substituent variation on the oxygen evolution rate by modulating the substitution ratio of side-chain ligands on MOFs, thereby altering their microstructure and charge distribution. The incorporation of a suitable quantity of amino groups, that act as strong electron-donating groups, facilitated the effective separation of electron-hole pairs generated during the photocatalytic process. However, an excessive introduction of amino groups can result in a reduction in both pore structure and surface area, thereby impeding the efficiency of the photocatalytic oxygen evolution reaction.

Excitonic Effects of the Excited-State Photocatalytic Reaction at the Molecule/Metal Oxide Interface.

Excitonic effects caused by the Coulomb interaction between electrons and holes play a crucial role in photocatalysis at the molecule/metal oxide interface. As an ideal model for investigating the excitonic effect, coadsorption and photodissociation of water and methanol molecules on titanium dioxide involve complex ground-state thermalcatalytic and excited-state photocatalytic reaction processes. Herein, we systemically investigate the excited-state electronic structures of the coadsorption of H2O and CH3OH molecules on a rutile TiO2(110) surface by linear-response time-dependent density functional theory calculations and probe the reaction path for generating HCOOH or CO2, from ground-state and excited-state perspectives. The reaction barriers in excited-state calculations are significantly different from those in ground-state calculations during three processes, with the largest decrease being 0.94 eV for the Ti5c-O-CH2-O-Ti5c formation process.

Experimental investigation on parameter optimization of liquid spectral beam splitter for continuous photocatalytic hydrogen production accompanied with photovoltaic power generation under solar full spectrum

Effective utilization of solar energy is of great significance for a sustainable future. Herein, we report a cascade system for hydrogen-electricity co-production (PH-PV) utilizing solar full spectrum. The output performance of the system can be precisely adjusted by controlling certain parameters of liquid spectral beam splitter (LSBS) which contains TiO2 nanoparticle suspension simultaneously generating hydrogen via a photocatalytic reaction process. Typically, the thickness of LSBS, the loading amount of TiO2, the flowrate of suspension and the light intensity have been investigated in detail. It is found that LSBS is necessary in our system as it could ensure the safe operation of PV while the light intensities larger than 8 suns. With the decrease of the thickness or loading amount of photocatalyst, more electricity could be produced by PV module but less hydrogen from PH module. Further increase of above two parameters simultaneously could lead to aggregation and settlement of particle suspension in LSBS, which is detrimental to the optical absorbance of the system. Besides, changing the flowrate will diversify the surface features of particles by shear-induced effect. At optimal flowrate, the particles in LSBS could exhibit oscillation characteristics under synergistic effect of shear force and gravity, which would lead to excellent light absorption and transmittance. Furthermore, an obvious gain for both hydrogen and electricity output and system efficiency could be obtained through increasing light intensity appropriately. Finally, the improved merit function (MF) was employed to evaluate the performance of hybrid system and more obvious effect of flowrate on MF value than other parameters was found. The optimal MF value of 3.07 was reached when flowrate was 60 mL/min. Our work is expected to provide important guidance for the optimization of PH-PV cascade system driven by outdoor direct solar energy.