Photocatalytic Nanocomposites Research Articles

Synthesis and characterisation of visible light-responsive Fe-doped BiOCl NPs and their application for the remediation of textile dye by LED irradiation

ABSTRACT In the present research work, Fe-doped bismuth oxychloride (Fe-doped BiOCl) photocatalyst is synthesised through the precipitation technique, and the mineralisation of textile dye is investigated in the presence of light-emitting diode (LEDs) irradiation (400–700 nm). The prepared photocatalysts were characterised through various spectroscopic techniques for the detailed morphological, elemental and surface properties. The UV–vis absorbance maxima of Fe-doped BiOCl by UV-Vis was near 358 nm, while the band gap was 4.8 eV which is comparatively higher than the average value. Fourier transform infrared spectra showed typical bands of Fe doped BiOCl at 506 cm−1, 1601, 2337 and at 3565.0 cm−1. From the X-ray diffraction (XRD) pattern, the crystalline nature of the Fe-doped nanocomposite was confirmed whose calculated crystallite size was 41.12 nm. The major and sharp two theta peaks of XRD were at 11.95°, 24.07°, 25.81°, 32.46°, 33.39°, 36.47°. The microscopic technique showed that the size of the nanocomposite was 200–400 nm which was in the form of small nanosheets. The energy dispersive X-ray spectroscopy (EDS) showed peaks for Bi, O, Cl and Fe 36.91%, 26.48%, 36.37% and 0.24%, respectively, indicating the formation of the nanocomposite. The BET surface area of the Fe-doped BiOCl photocatalyst was 10.224 m2/g, while the pore volume was 0.065 cc/g. Further, the potential of the developed photocatalytic nanocomposite was evaluated for the photocatalytic degradation of the ethyl violet dye from the aqueous solutions. Various optimisation parameters have been discussed, and it has been found that 89% of the dye was degraded in 125 min with a 5.11 × 10−4 s−1 rate constant. The photocatalyst had shown excellent reusability and stability during the degradation of ethyl violet. The photocatalytic activity of Fe-doped BiOCl was compared with other photocatalysts and current literature and exhibited enhanced efficiency.

ZnO/TiO2 photocatalytic nanocomposite for dye and bacteria removal in wastewater

This study investigates ZnO/TiO2 nanocomposites synthesized by the sol–gel method for their potential application in textile wastewater treatment. The physicochemical properties of these materials were comprehensively characterized using various analytical techniques, including transmission electron microscopy (TEM), x-ray diffraction (XRD) analysis, x-ray fluorescence (XRF) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and UV–visible (UV-Vis) spectroscopy. XRD and XRF analyses confirmed the formation of a ZnO/TiO2 heterostructure. TEM images revealed a quasi-spherical morphology with slight agglomeration. The ZnO/TiO2 nanocomposite with a 1:5 molar ratio of Zn(II):Ti(IV) showed the highest BET surface area (91.345 m2 g−1) and the narrowest band gap (Eg = 3.06 eV). This composite demonstrated efficient degradation of methylene blue dye under sunlight irradiation and exhibited 100% antibacterial activity against S. typhi and S. aureus at concentrations ≥5 mg ml−1, indicating its potential for treating textile wastewater.

Fabrication of a hyphenated S-scheme and Schottky-junction photocatalyst based on a ternary TiNbCTx@α-Bi2O3/ZnSe heterostructure with enhanced optical and photoelectrochemical properties

Environmental pollution by pharmaceuticals poses a serious threat to humans and animals. Hence there is a need for a low-cost, environmentally friendly, and sustainable treatment technology for environmental remediation. Herein, we report the synthesis of a novel TiNbCTx@α-Bi2O3/ZnSe ternary photocatalytic nanocomposite, characterised using spectroscopic and microscopic techniques. Moreover, the optical and photoelectrochemical properties of the photocatalysts were assessed using spectroscopic tools such as UV–Vis DRS, EIS and PL. The synthesised pristine, cubic ZnSe, monoclinic Bi2O3, α-Bi2O3/ZnSe and the ternary composites’ crystallinity were all confirmed by the co-existence of their crystal planes and bands in XRD, SAED, and Raman spectroscopy, correspondingly. SEM and TEM analysis confirmed the anticipated characteristic morphologies and the interfaces. Improved optical properties deduced from UV–Vis DRS measurements revealed α-Bi2O3 and ZnSe to have band gaps of 2.7 eV and 2.41 eV, respectively. Upon creating an α-Bi2O3/ZnSe heterostructure and TiNbCTx@α-Bi2O3/ZnSe ternary system, a red shift was observed in their band gaps, indicating improved optical properties. The electrochemical properties of the materials were determined using EIS. These were used to deduce the charge transfer kinetics of the heterostructure and ternary system, which showed TiNbCTx@α-Bi2O3/ZnSe to be an outstanding photocatalyst over the synthesised pristine materials and α-Bi2O3/ZnSe heterostructure. The photocurrent response of the TBZ-7 % exhibited enhanced generation and separation of photoexcited charge carriers 4 folds higher than those of pristine materials. The PL spectra of the TBZ-7 % showed low intensity due to the suppression of charge recombination rates. Moreover, the Nyquist and LSV plots of TBZ-7 % presented improved charge transfer ability and a prolonged lifetime of photoinduced charge carriers (280 ms), respectively. With these enhanced properties, TiNbCTx@α-Bi2O3/ZnSe ternary photocatalytic nanocomposite demonstrates the extraordinary potential for environmental remediation in degrading ARVs from water.

Enhancement of visible-light photocatalysis of TiO2 via nanocomposite incorporating with Fe(III) species

This paper introduces a novel approach for the synthesis of photocatalytic nanocomposites via a fast reaction occurring at ambient conditions between the strong base NaOH and FeCl3 solution to obtain a fresh precipitate of Fe(OH)3 in the presence of TiO2 nanoparticles. FE-SEM analysis revealed a restructured state of TiO2 particles on the surface of colloidal Fe(OH)3. Solid-phase studies, including XRD and FT-IR, indicated a phase transformation from Fe(OH)3 to γ-Fe2O3 during the formation of the nanocomposite. UV–Vis diffuse reflectance measurements confirmed a significant reduction in the band gap of the synthesized composite, indicating its potentials as a photocatalyst under visible light irradiation. Another advantage of this composite type is its rapid sedimentation ability within minutes, facilitating post-processes such as phase separation and catalyst reuse on a large scale, which are challenging in the case of TiO2 nanoparticles. Inducing photocatalysis under visible light, the efficiency in degrading persistent colorants was demonstrated through a case study of indigo carmine (IC), which exhibited a threefold improvement in degradation efficiency for the case of the nanocomposite compared to the original TiO2. Indeed, the IC degradation process was studied in consideration of various factors such as Fe/Ti ratio in the catalyst, illumination time, colorant concentration, catalyst dosage, and pH of the environment. Additionally, mineralization studies confirmed the oxidation of IC to CO2 rather than the formation of potentially toxic intermediates. Furthermore, the stability of the catalyst was examined through six cycles of reuse.

Synergistic effect of ZnO/Ag2O@g-C3N4 based nanocomposites embedded in carrageenan matrix for dye degradation in water

This research achieved success by synthesizing innovative nanocomposite composed of zinc oxide (ZnO), graphitic carbon nitride (g-C3N4) and silver oxide (Ag2O) nanomaterials incorporated into a carrageenan matrix, thus creating an environmentally friendly and stable support structure. The synthesis process involved hydrothermal and chemical precipitation methods to create photocatalytic g-C3N4, ZnO, and Ag2O nanocomposites. The success is evident through the characterization results, which unveiled distinctive peaks corresponding to Zn–O (590-404 cm−1) and Ag–O (2072 cm−1) stretching in the Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses, conclusively confirming the successful synthesis of g-C3N4, ZnO, Ag2O, and their respective nanocomposites. Further validation through a scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDX) and elemental mapping affirmed the presence of Zn, O, Ag, C, and N. Additionally, transmission electron microscope (TEM) imaging unveiled the nanosheet morphology of g-C3N4, the nanorod structure of ZnO, and the spherical form of Ag2O nanomaterials. ZnO and Ag2O nanomaterials demonstrated a consistent 10–20 nm size range. To underscore their ability to harness visible light, the nanomaterials were excited at 380 nm, emitting visible light emission within the 400–450 nm range. The synthesized nanocomposites showcased outstanding adsorption and photocatalytic properties, achieving efficiency ranging from 80 % to 98 %, attributed to the synergistic interactions between the various components. These findings culminate in a confirmation of the research's success, validating the exceptional potential of these nanocomposites for various applications.

TiO2/AgBr nanocomposite as a novel hydrophilic and photocatalytic modifier in the fabrication of polyethersulfone membrane for wastewater treatment

Enhancing the performance of filtration membranes to improve their antifouling, permeability, and stability is a crucial objective. This can be acquired through the development of innovative materials and methods. With this in mind, the exertion of novel materials is considered a promising approach for modifying polymeric membranes. This study focuses on the potential of incorporating TiO2/AgBr photocatalytic nanocomposites to improve the hydrophilicity, antifouling, and permeability of polyethersulfone (PES) membranes. Following the synthesis of TiO2/AgBr, the study examines its impact on the performance of PES membranes by introducing various concentrations of TiO2/AgBr nanocomposite. Notably, the water contact angle significantly decreases from 68.5° to 44.2°, indicating an improvement in hydrophilicity. This enhanced overall porosity leads to almost a twofold increase in pure water permeability, with the bare membrane registering 78.3 L/m2h.bar and the membrane containing 0.2 wt% TiO2/AgBr achieving 152.4 L/m2h.bar. Due to the photocatalytic activity of TiO2/AgBr, the modified membranes demonstrate promoted antifouling performance, when UV irradiation is used in the washing step of the fouled membranes, as evidenced by the increased flux recovery ratio values, rising from 48 to 60.6 %. The rejection of two different dyes was assessed and the results of 83.9 % and 95.2 % rejection were obtained for Reactive Black 5 (RB5) and Lanasol Red 6G, respectively. Furthermore, the antibacterial activity of TiO2/AgBr was also indicated by confocal microscopy analysis. Thus, embedding TiO2/AgBr not only enhances antifouling properties but also improves the membranes’ ability to reject dyes effectively.

A facile method for boosting the graphitic carbon nitride's photocatalytic activity based on 0D/2D S-scheme heterojunction nanocomposite architecture

Graphitic carbon nitride (g-C3N4) has received significant interest as a metal-free photocatalyst. The S-scheme photocatalytic system has great potential to improve the charge separation in semiconductor photocatalysts. In this study, we have fabricated non-toxic and low-cost photocatalytic nanocomposites of 0D/2D S-scheme heterojunction composed of iron oxide and graphitic carbon nitride by a facile method. The developed facile method provides a sustainable way with a high atom economy to further enhance the photocatalytic performance of exfoliated g-C3N4. The 0D-iron oxide/2D-C3N4 exhibited nearly 10 times better than bulk g-C3N4 and almost 60 % better than exfoliated g-C3N4 under simulated solar light irradiation. The experimental results demonstrated that the effective charge-carrier mechanism led to an improved generation of reactive oxygen species (ROSs), resulting in an impressive photocatalytic performance. A serial photocatalytic test was also conducted to understand photocatalytic reaction mechanisms with various scavengers.

Synthesis of CQDs/MIL-101(Cr) photocatalytic nanocomposite for degradation of RR-195

Synthesis of CQDs/MIL-101(Cr) photocatalytic nanocomposite for degradation of RR-195

Novel Bi-Functional MoS2/α-Fe2O3 Nanocomposites for High Photocatalytic Performance

In this study, 3-dimensional molybdenum disulfide (MoS2) structures, integrated with hematite (α-Fe2O3) nanoparticles, were fabricated under a convenient two-step hydrothermal route. The fabricated photocatalytic nanocomposites consist of well-arranged MoS2 flakes, resembling spherical flower-like morphology, and the nanoparticulate α-Fe2O3 structures decorate the 3D network. By raising the α-Fe2O3 weight ratio, the composites’ specific surface area and morphology were not affected, regardless of the partial cover of the cavities for higher hematite content. Moreover, the crystallinity examination with XRD, Raman, and FTIR techniques revealed that the precursor reagents were fully transformed to well-crystalized MoS2 and Fe2O3 composites of high purity, as no organic or inorganic residues could be detected. The photocatalytic oxidation and reduction performance of these composites was evaluated against the tetracycline pharmaceutical and the industrial pollutant hexavalent chromium, respectively. The improvement in the removal efficiencies demonstrates that the superior photoactivity originates from the high crystallinity and homogeneity of the composite, in combination with the enhanced charge carriers’ separation in the semiconductors’ interface.

Synthesis of novel maghemite (γ-Fe2O3)-decorated g-C3N4 nano-tubes (g-C3N4 NTs/γ-Fe2O3) photocatalytic nano-composite for ultrafast degradation of organics in wastewater: Insight into the mechanism of photoexcited charge separation

In this study, to enhance the photodegradation of organic pollutants including Methyl blue (MB) and Methyl orange (MO), mesoporous tubular g-C3N4/γ-Fe2O3 (FCN) nano-composite synthesized via facile procedures. FT-IR and XRD data proved the existence of maghemite (γ-Fe2O3) nanoparticles on the g-C3N4 nano-tubes. Experimental data showed that among fabricated photocatalysts, FCN exhibited the highest activity rate toward the photodegradation of MB (%96.1/60 min) and MO (%98.3/120 min) with an excellent kinetic rate of 0.0509 min−1 (MB) and 0.0352 min−1 (MO) under visible light and considerable photocatalytic stability after six cycles. In addition, the visible light-harvesting-capability of FCN enhanced compared to unequipped forms of g-C3N4 (BCN and CNNTs), surprisingly functioning under irradiation of photons greater than 900 nm, proving the synergistic role of γ-Fe2O3 nanoparticles not only in harvesting visible light but also in hindering electron-hole recombination. BET analysis showed mesoporous structure, the highest SSA and pore volume (55.623 m2/g, 0.1699 cm3/g) for FCN, indicating more active sites and enhanced target molecules adsorption, then augmented photocatalytic performance in comparison to the rest of the samples. Finally, FCN generated an excellent photocurrent density (3.76 μA/cm2) with the least arc radius, introducing a high-potential hybrid photocatalyst to the research field.

ZnO Precursor’s ability to catalyze formation of reactive oxygen species to degrade aqueous organic pollutants

Advanced oxidative processes (AOP) could mitigate emerging and persistent pollutants in drinking water. Yet there is a dearth of economical materials to generate the reactive oxygen species (ROS) that are responsible for pollutant degradation in AOPs. In this work, we design a zinc hydroxychloride monohydrate (ZHCM) silicon dioxide photocatalytic nanocomposite to generate ROS for non-selective degradation of drinking water contaminants. ZHCM is an intermediate phase in the sol–gel synthesis of ZnO-SiO2-Ag nanocomposites containing 63–100 % ZnO. Typically, ZHCM is calcinated around 500 °C to crystallize into ZnO, yet we find that this calcination step may decrease photocatalytic activity. ZHCM exhibited higher methylene blue degradation efficiency through both catalysis (31 % after 4 h) and photocatalysis (98 % after 4 h) compared to the ZnO composites (∼0% and 78 % after 4 h). ZHCM had the highest photodegradation efficiency for ciprofloxacin and caffeine. The increased catalytic and photocatalytic activity of these model pollutants is attributed to the generation of two ROS: superoxide anions in UV light and peroxide anions in the absence of light. These ROS were identified using a new modified biological assay measuring the chemiluminescence of luminol in the presence of horseradish peroxidase. Results are further verified via scavenger quenching tests. The ZHCM and ZnO-SiO2-Ag are characterized for their antimicrobial activity measured by E. coli growth inhibition zones, band gaps, crystalline domains, and surface areas. This work demonstrates the potential to synthesize, at lower temperatures, a photocatalyst with enhanced ROS generation and reduced UV dependency.

Development of an antimicrobial inorganic polymer based on fly ash and metakaolin incorporated by nano-TiO2 for reactive dye removal

Advanced and eco-friendly construction materials are being developed to reduce pollution and improve wastewater treatment efficiency. One such material is a photocatalytic nanocomposite that uses industrial wastes and natural substances to eliminate pollution. A recent study explored using an inorganic polymer composite (FM) made from a mixture of 70% fly ash and 30% metakaolin, with sodium hydroxide and sodium silicate as an alkali activator. The study evaluated the mechanical and hydration characteristics of the FM composite after 28 days in 100% humidity at room temperature. The study also examined the effect of adding 2.5 wt.% of Nano-TiO2 to FM composite and how it affects its properties. Results indicate that adding Nano-TiO2 to FM composite enhances its mechanical, antibacterial, and photocatalytic capabilities. Specifically, FM-TiO2 composite showed 90% removal of reactive blue 19 dye effluent in sunlight after 90 min, making it an excellent choice for sustainable wastewater treatment. This study presents a cost-effective, eco-friendly solution to wastewater treatment, with added antimicrobial properties from Nano-TiO2.

Green Hydrogen Generation from Eco-Friendly and Cost-Effective Red Sea Water Using a Highly Photocatalytic Nanocomposite Film, As2O3/Poly-3-methylaniline

The primary objective of this research is to address the energy challenges by introducing an innovative nanocomposite material. This material is designed to facilitate the conversion of environmentally friendly and economically viable Red Sea water into hydrogen gas. The ultimate goal of this work is to pave the way for the development of a practical device that can be employed within households and industrial settings to directly convert water into hydrogen gas. This novel nanocomposite material synthesized through oxidative polymerization comprises As2O3 and Poly-3-methylaniline (P3MA). This material possesses an extensive absorption range, spanning up to 700 nm, and features a bandgap of 1.75 eV, making it a promising candidate for use as a photoelectrode in green hydrogen production. The unique aspect of this setup lies in the utilization of Red Sea water, a natural sacrificing agent, as the electrolyte, rendering the process eco-friendly and cost-effective. When it is employed as a photoelectrode, this material exhibits high sensitivity to green hydrogen production, generating 6 moles/10 cm2·h of hydrogen. At a voltage of −0.83 V, the current density values are measured as −0.08 mA·cm−2 (Jph) in light and −0.02 mA·cm−2 (Jo) in darkness. Furthermore, the photoelectrode’s responsiveness to light is assessed with different optical filters, revealing the optimal performance at 340 nm, where Jph reaches −0.052 mA·cm−2. These outcomes provide strong evidence of the photoactivity of the As2O3/P3MAphotoelectrode for green hydrogen production using Red Sea water. This underscores its potential for the development of an electrochemical cell for the direct conversion of sea water into H2 gas.

Carbon Dots–TiO2 Nanocomposites for the Enhanced Visible‐Light Driven Photodegradation of Methylene Blue

AbstractHerein, the conjugation of carbon dots (CDs) with TiO2 nanoparticles is reported to prepare a photocatalytic nanocomposite for an enhanced visible‐light‐driven photodegradation of methylene blue (MB). CDs are prepared from citric acid (CA) and ethylenediamine (EDA) via hydrothermal treatment. Using MB as a model pollutant, it is observed that, under visible‐light irradiation, the nanocomposite presents an increment of the catalytic performance of 367% when compared to bare TiO2. This is achieved because the addition of CDs leads to increased visible‐light absorption and hinders the recombination of photogenerated charge carriers. Thus, CDs are capable of bridging some of the limitations posed by TiO2. Tests using reactive species scavengers indicate that the main active species involved in the photodegradation by the nanocomposites are superoxide radicals followed by hydroxyl radicals, which differs from bare TiO2. Lastly, a life cycle assessment (LCA) study shows that, when accounting for performance, the nanocomposites have lower relative environmental impacts than bare TiO2. In addition, the safety of the produced CDs is shown by in vitro assays. In summary, due to conjugation with CDs, a relevant increment in the catalytic performance of TiO2 is achieved; providing an important step toward the sustainable rational design of active visible‐light‐driven photocatalysts.

MOF based nanocomposites for photocatalytic degradation of pollutants in water: A critical review

Metal-organic framework (MOF) based nanocomposites have a wide range of applications; however, research output indicates that MOF based nanocomposites have attracted great attention in the area of water treatment, particularly photodegradation of water pollutants. This comes as a result of high water pollution, water scarcity, poor drinking water quality and the emerging of tenacious micropollutants found in water bodies. Majority of water pollutants can be treated via photocatalytic processes and MOF is a remarkable modifying and support material for photocatalytic nanomaterials. MOF have tremendous physicochemical properties which provide opportunities for unique fabrication and modification of photocatalytic nanocomposites with enhanced efficiency, recovery, recyclability and reusability in water treatment. In this review, MOF-based nanocomposites, fabrication techniques, classifications, mechanisms as well as challenges and future prospects for the photocatalytic degradation of pollutants in water are investigated and discussed.

Developing Self-Cleaning Photocatalytic TiO2 Nanocomposite Coatings

Photocatalytic coatings with self-cleaning properties are becoming increasingly more popular due to the increased awareness of the importance of cleaning and the associated high cost of cleaning supplies and services. This research investigated self-cleaning photocatalytic polydimethylsiloxane (PDMS)/titanium dioxide (TiO2) nanocomposite coatings and focused on selecting the optimal TiO2 phase and concentration. To date, the comparison of the different TiO2 phases as a nanocomposite coating has not been sufficiently considered. PDMS/TiO2 nanocomposite coatings with three nanomaterial (NM) samples (an anatase, rutile, and mixed phase) and three concentrations of TiO2 (0.6, 1 and 3 w/v%) were prepared, applied to glass slides by dip coating, and tested with respect to hydrophobicity, surface stability, antifogging, and photocatalytic properties. It was found that a stable hydrophobic coating with the optimal photocatalyitc performance was produced with 3 w/v% anatase TiO2.

Visible light-driven photocatalytic degradation of fluoroquinolone drugs in water over plasmonic Ag/ZnNb2O6@SC3N4 indirect Z-scheme nanostructures

The fabrication of visible light responsive heterojunction photocatalyst with efficient charge separation and transfer is an important quest in the exploitation of photocatalysis for environmental remediation. In this work, a ternary heterostructure comprising of zinc niobate (ZnNb2O6) coupled with sulphur-doped graphitic carbon nitride (SC3N4) and decorated with varying loadings of silver nanoparticles (Ag NPs) was obtained using ultrasonic synthesis. The photocatalysts were characterized extensively using various microscopic, spectroscopic, and electrochemical analytical techniques. The 5 wt%Ag/ZnNb2O6 @SC3N4 heterojunction showed the highest degradation efficiencies towards the antibiotic drugs; levofloxacin (LVF, 94.6 % removal) and ofloxacin (OFX, 98.0 % removal) in just 60 min of visible light irradiation. This activity is nearly 5 times and 3.5 times higher than that over ZnNb2O6 @SC3N4 for LVF and OFX, respectively, which indicates the importance of incorporating the Ag NPs towards better visible utilization, improved charge separation efficiency and lower charge transfer resistance. The influence of pH, photocatalyst dose and initial concentration of pollutant were investigated. Finally, a typical Ag NPs mediated indirect Z-Scheme charge transfer mechanism was proposed to describe the formation of the reactive species and subsequent degradation of the pollutants. This work demonstrates a systematic design of simple but efficient photocatalytic nanocomposites with the capability to ameliorate a wide variety of fluoroquinolone drugs, which is significant towards pharmaceutical pollution mitigation.

Carbon dots driven directional charge migration on sulfur vacancy enriched ZnIn2S4 nanosheets for enhanced photocatalytic hydrogen evolution

Sulfur vacancy as a kind of intrinsic defect for metal sulfides plays an important role in adjusting the electronic structure, but the uncontrollability of the regulation does not always lead to efficient activity in photocatalytic hydrogen production. To address this issue, a photocatalytic nanocomposite is designed and constructed by in situ inserting carbon dots (CDs) into ultrathin ZnIn2S4 (ZIS) nanosheets with sulfur vacancies (CDs/Vs-ZIS) by a one-step hydrothermal method. The charge transfer kinetics analysis of CDs/Vs-ZIS demonstrates that the trapped electrons by sulfur vacancies are directed transferred to the surface of CDs. The electron sink effect leads to further enhancement of the charge separation efficiency on CDs surface and CDs act as hydrogen-producing active sites to greatly improve the hydrogen evolution. Benefiting from the directional charge migration driven by CDs in Vs-ZIS nanosheets, the optimal CDs/Vs-ZIS photocatalyst exhibits a superior photocatalytic hydrogen evolution rate of 5.93 mmol g−1h−1.

A floatable photocatalytic nanocomposite to facilitate scale-up of solar hydrogen production.

A floatable photocatalytic nanocomposite to facilitate scale-up of solar hydrogen production.

Floatable photocatalytic hydrogel nanocomposites for large-scale solar hydrogen production.

Storing solar energy in chemical bonds aided by heterogeneous photocatalysis is desirable for sustainable energy conversion. Despite recent progress in designing highly active photocatalysts, inefficient solar energy and mass transfer, the instability of catalysts and reverse reactions impede their practical large-scale applications. Here we tackle these challenges by designing a floatable photocatalytic platform constructed from porous elastomer-hydrogel nanocomposites. The nanocomposites at the air-water interface feature efficient light delivery, facile supply of water and instantaneous gas separation. Consequently, a high hydrogen evolution rate of 163 mmol h-1 m-2 can be achieved using Pt/TiO2 cryoaerogel, even without forced convection. When fabricated in an area of 1 m2 and incorporated with economically feasible single-atom Cu/TiO2 photocatalysts, the nanocomposites produce 79.2 ml of hydrogen per day under natural sunlight. Furthermore, long-term stable hydrogen production in seawater and highly turbid water and photoreforming of polyethylene terephthalate demonstrate the potential of the nanocomposites as a commercially viable photocatalytic system.