Visible Light-Driven Pure Water Splitting by a Nature-Inspired Organic Semiconductor-Based System

Unraveling the Interfacial Charge Migration Pathway at the Atomic Level in a Highly Efficient Z-Scheme Photocatalyst

A highly efficient Z-scheme photocatalytic system constructed with 1D CdS and 2D CoS₂ exhibited high photocatalytic hydrogen-evolution activity of 5.54 mmol h^-1  g^-1 with an apparent quantum efficiency of 10.2 % at 420 nm. More importantly, its interfacial charge migration pathway was unraveled: The electrons are efficiently transferred from CdS to CoS₂ through a transition atomic layer connected by Co-S_5.8 coordination, thus resulting in more photogenerated carriers participating in surface reactions. Furthermore, the charge-trapping and charge-transfer processes were investigated by transient absorption spectroscopy, which gave an estimated charge-separation yield of approximately 91.5 % and a charge-separated-state lifetime of approximately (5.2±0.5) ns in CdS/CoS₂ . This study elucidates the key role of interfacial atomic layers in heterojunctions and will facilitate the development of more efficient Z-scheme photocatalytic systems.

A visualizable means for verifying the manner of charge transfer in WO3-based type-II heterostructures

Research into photocatalytic mechanisms and charge carrier transfer is of vital significance. For type-II heterostructures containing WO3, a visualizable means is proposed for the first time for verifying the manner of charge transfer via observing the photochromism of WO3. The accuracy of this visualizable means is evidenced through corresponding characterization, such as XPS and OCP. In addition, photocatalytic H2 evolution as a supporting proof is studied to prove the manner of charge transfer owing to the inactivity of WO3. If the charge transfer pathway principally follows a conventional type-II manner, the heterostructure will change color from yellow to a dark color and show lower activity compared with the individuals. However, if the charge transfer primarily follows a Z-scheme mechanism, the color won't show a noticeable change but much higher activity will be exhibited than that by the individual components. CdS-WO3 and ZnIn2S4-WO3 (ZIS-WO3) are used as examples to verify the universality of this method and exclude the impact of the crystal phase of WO3 on photochromism.

Polymeric Donor-Acceptor Heterostructures for Enhanced Photocatalytic H2 Evolution without Using Pt Cocatalysts

Polymeric carbon nitride (CN) is a promising material for photocatalytic water splitting. However, CN in its pristine form tends to show moderate activity due to fast recombination of the charge carriers. The design of efficient photocatalytic system is therefore highly desired, but it still remains a great challenge in chemistry. In this work, a pyrene-based polymer able to serve as an electron donor to accelerate the interface charge carrier transfer of CN is presented. The construction of donor-acceptor (D-A) heterojunction was confirmed to significantly restrain the charge recombination and, thus, improve the proton reduction process. This study provides a promising strategy to achieve solar H₂ production in an efficient and low-cost manner.

Conjugated Polymers with Oligoethylene Glycol Side Chains for Improved Photocatalytic Hydrogen Evolution

Conjugated polymers are emerging as promising organic photocatalysts for hydrogen evolution from water. However, it is still very challenging for conjugated polymers to realize highly efficient photocatalytic hydrogen evolution. Herein, we demonstrate an efficient strategy of hydrophilic side chain functionalization to boost the hydrogen evolution rates of conjugated polymers. By functionalizing conjugated polymers with hydrophilic oligo (ethylene glycol) monomethyl ether (OEG) side chains, a 90-fold improvement in hydrogen evolution rate has been achieved than that of alkyl-functionalized conjugated polymer. It is found that the OEG side chains interact robustly with Pt co-catalysts, resulting in more efficient charge transfer. Moreover, OEG side chains in conjugated polymers can adsorb H⁺ from water, resulting in significantly lowered energy levels on the surfaces of conjugated polymers, which enables cascade energy levels and enhances charge separation and photocatalytic performance. Our results indicate that rational side-chain engineering could facilitate the design of improved organic photocatalysts for hydrogen evolution.

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Conjugated polymers with oligoethylene glycol side chains are prepared

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Oligoethylene glycol side chains improve photocatalytic hydrogen evolution rates

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Oligoethylene glycol side chains interact robustly with Pt co-catalysts

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Oligoethylene glycol side chains enable cascade energy levels

Fabrication of CdTe QDs/BiOI-Promoted TiO2 Hollow Microspheres with Superior Photocatalytic Performance Under Simulated Sunlight

Hollow and heterostructured architectures are recognized as an effective approach to improve photocatalytic performance. In this work, ternary TiO₂/CdTe/BiOI with hollow structure was constructed via a step-by-step method. In addition, the effect of TiO₂ structural regulation and the energy band alignment of BiOI and CdTe quantum dots (CdTe QDs) with TiO₂ in TiO₂/CdTe/BiOI on photocatalytic dye removal were also studied. The results reveal that the TiO₂/CdTe/BiOI heterostructures with hollow substrates exhibit much higher photocatalytic activities than pure TiO₂, P25, TiO₂/CdTe, and TiO₂/BiOI and ternary TiO₂/CdTe/BiOI with solid substrates. For TiO₂(H)/CdTe/BiOI, several synergistic factors may be responsible for the remarkable visible-light photodegradation performance, such as strong visible-light absorption by BiOI and larger specific surface area.

Black Phosphorus, a Rising Star 2D Nanomaterial in the Post-Graphene Era: Synthesis, Properties, Modifications, and Photocatalysis Applications

Semiconductor photocatalysis, a sustainable and renewable technology, is deemed to be a new path to resolve environmental pollution and energy shortage. The development of effective photocatalysts, especially the metal-free photocatalysts, is a critical determinant of this technique. The recently emerged 2D material of black phosphorus with distinctive properties of tunable direct bandgap, ultrahigh charge mobility, fortified optical absorption, large specific surface area, and anisotropic structure has captured enormous attention since the first exfoliation of bulk black phosphorus into mono- or few layered phosphorene in 2014. In this article, the state-of-the-art preparation methods are first summarized for bulk black phosphorus, phosphorene, and black phosphorus quantum dot and then the fundamental structure and electronic and optical properties are analyzed to evaluate its feasibility as a metal-free photocatalyst. Various modifications on black phosphorus are also summarized to enhance its photocatalytic performance. Furthermore, the multifarious applications such as solar to energy conversion, organic removal, disinfection, nitrogen fixation, and photodynamic therapy are discussed and some of the future challenges and opportunities for black phosphorus research are proposed. This review reveals that the rising star of black phosphorus will be a multifunctional material in the postgraphene era.

Hollow BiVO4/Bi2S3 cruciate heterostructures with enhanced visible-light photoactivity

Unique BiVO₄/Bi₂S₃ cruciate hollow heterostructures are successfully constructed via anion exchange reactions using cruciate BiVO₄ as templates and precursors. The hollow heterostructures exhibit excellent enhanced photocurrent response and photocatalytic activity for reduction of Cr⁶⁺ under visible-light illumination.

Large enhanced photocatalytic activity of g-C3N4 by fabrication of a nanocomposite with introducing upconversion nanocrystal and Ag nanoparticles

A novel heterostructured nanocomposite UCNPs@SiO2@Ag/g-C3N4 was developed for the first time to substantially boost the solar-light driven photocatalytic activity of g-C3N4. Its photocatalytic properties and photocatalytic mechanism were investigated. The as-synthesized photocatalyst with excellent improvement in the solar absorption and separation efficiency of photoinduced electron-hole pairs exhibited optimum solar-induced photocatalytic activity in dye degradation and hydrogen production. The experimental results showed that the rates of degradation of Rhodamine B (RhB) and hydrogen evolution were about 10 and 12 times higher than that of pristine g-C3N4, respectively. The excellent photocatalytic activity was attributed to the synergetic effect of upconversion nanoparticles (UCNPs) and Ag nanoparticles (NPs) on the modification of the photocatalytic properties of g-C3N4, resulting in a broad light response range for g-C3N4 as well as the fast separation and slow recombination of photoinduced electron-hole pairs. This study provides new insight into the fabrication of g-C3N4-based nanocomposite photocatalysts with high catalytic efficiency through the artful assembly of UCNPs, Ag NPs and g-C3N4 into a hetero-composite nanostructure. The prominent improvement in photocatalytic activity enables the potential application of g-C3N4 in the photocatalytic degradation of organic pollutants and hydrogen production utilizing solar energy.

Metal-Free Graphitic Carbon Nitride Photocatalyst Goes Into Two-Dimensional Time

Graphitic carbon nitride (g-C₃N₄) is always a research hotspot as a metal-free visible-light-responsive photocatalyst, in the field of solar energy conversion (hydrogen-production by water splitting). This critical review summarizes the recent progress in the design and syntheses of two-dimensional (2D) g-C₃N₄ and g-C₃N₄-based nanocomposites, covering (1) the modifications of organic carbon nitrogen precursors, such as by heat treatment, metal or metal-free atoms doping, and modifications with organic functional groups, (2) the influencing factors for the formation of 2D g-C₃N₄ process, including the calcination temperature and protective atmosphere, etc. (3) newly 2D g-C₃N₄ nanosheets prepared from pristine raw materials and bulk g-C₃N₄, and the combination of 2D g-C₃N₄ with other 2D semiconductors or metal atoms as a cocatalyst, and (4) the structures and characteristics of each type of 2D g-C₃N₄ systems, together with their optical absorption band structures and interfacial charge transfers. In addition, the first-principles density functional theory (DFT) calculation of the g-C₃N₄ system has been summarized, and this review provides an insightful outlook on the development of 2D g-C₃N₄ photocatalysts. The comprehensive review is concluded with a summary and future perspective. Moreover, some exciting viewpoints on the challenges, and future directions of 2D g-C₃N₄ photocatalysts are discussed and highlighted in this review. This review can open a new research avenue for the preparation of 2D g-C₃N₄ photocatalysts with good performances.

Recent Progress in Constructing Plasmonic Metal/Semiconductor Hetero-Nanostructures for Improved Photocatalysis

Hetero-nanomaterials constructed by plasmonic metals and functional semiconductors show enormous potential in photocatalytic applications, such as in hydrogen production, CO2 reduction, and treatment of pollutants. Their photocatalytic performances can be better regulated through adjusting structure, composition, and components’ arrangement. Therefore, the reasonable design and synthesis of metal/semiconductor hetero-nanostructures is of vital significance. In this mini-review, we laconically summarize the recent progress in efficiently establishing metal/semiconductor nanomaterials for improved photocatalysis. The defined photocatalysts mainly include traditional binary hybrids, ternary multi-metals/semiconductor, and metal/multi-semiconductors heterojunctions. The underlying physical mechanism for the enhanced photocatalysis of the established photocatalysts is highlighted. In the end, a brief summary and possible future perspectives for further development in this field are demonstrated.

Understanding structure-activity relationships in linear polymer photocatalysts for hydrogen evolution

Conjugated polymers have sparked much interest as photocatalysts for hydrogen production. However, beyond basic considerations such as spectral absorption, the factors that dictate their photocatalytic activity are poorly understood. Here we investigate a series of linear conjugated polymers with external quantum efficiencies for hydrogen production between 0.4 and 11.6%. We monitor the generation of the photoactive species from femtoseconds to seconds after light absorption using transient spectroscopy and correlate their yield with the measured photocatalytic activity. Experiments coupled with modeling suggest that the localization of water around the polymer chain due to the incorporation of sulfone groups into an otherwise hydrophobic backbone is crucial for charge generation. Calculations of solution redox potentials and charge transfer free energies demonstrate that electron transfer from the sacrificial donor becomes thermodynamically favored as a result of the more polar local environment, leading to the production of long-lived electrons in these amphiphilic polymers.

While inorganic semiconductors are well-studied for their solar-to-fuel energy conversion abilities, organic materials receive far less attention. Here, authors prepare linear conjugated polymers as H₂ evolution photocatalysts and rationalize photocatalytic activities with fundamental properties.

Bio-inspired Z-scheme g-C3N4/Ag2CrO4 for efficient visible-light photocatalytic hydrogen generation

Due to low charge separation efficiency and poor stability, it is usually difficult for single-component photocatalysts such as graphitic carbon nitride (g-C₃N₄) and silver chromate (Ag₂CrO₄) to fulfill photocatalytic hydrogen production efficiently. Z-scheme charge transport mechanism that mimics the photosynthesis in nature is an effective way to solve the above problems. Inspired by photosynthesis, we report Ag₂CrO₄ nanoparticles-decorated g-C₃N₄ nanosheet as an efficient photocatalyst for hydrogen evolution reaction (HER) with methanol as sacrificial agent. The formation of Z-scheme g-C₃N₄/Ag₂CrO₄ nanosheets photocatalysts could inhibit the recombination of photogenerated electron-hole pairs, promote the generation of hydrogen by photosplitting of water. The experiment results indicate that g-C₃N₄/Ag₂CrO₄ nanocomposites present enhanced photocatalytic activity and stability in the H₂ evolution of water splitting. And the nanocomposites g-C₃N₄/Ag₂CrO₄(23.1%) show the 14 times HER efficiency compared to that of bare g-C₃N₄.

2D Polymers as Emerging Materials for Photocatalytic Overall Water Splitting

Converting solar energy into storable and transportable chemical fuels using artificial photosynthetic systems can provide an alternative route to the current unsustainable use of fossil fuels, addressing the worldwide energy crisis and environmental issues. Recently, semiconducting polymers have emerged as a very promising class of photocatalysts for water splitting as their electronic and structural properties can be conveniently controlled and systematically designed at a molecular level. Among the various polymer photocatalysts that are reported so far, 2D polymer nanosheets are particularly interesting and gaining more attention. The 2D planar structure offers unique features such as high surface area, abundant surface active sites, efficient charge separation, and facile formation of heterostructures. The design and synthesis of 2D polymer nanosheets have greatly advanced the research in photocatalytic overall water splitting. Here, recent advances in developing photocatalysts based on 2D polymer nanosheets for photocatalytic overall water splitting are highlighted. Specifically, the existing approaches to tune their electronic structures and surface active sites for photocatalysis are discussed. Future opportunities and challenges for developing 2D polymers for photocatalytic overall water splitting are also included.

Coordinative integration of copper (II) and iron (II) phthalocyanine into amidoximated PAN fiber for enhanced photocatalytic activity under visible light irradiation

Metal phthalocyanine (MPc) complexes hold great promise for photocatalysis applications because of their high visible light harvesting efficiency and semiconductive properties. However, the effective development requires the suppression of their rapid charge recombination. Transition metal ions can act as electron traps to enhance the charge separation of semiconductors, but challenges still remain for bimetallic co-catalysis of MPc due to the difficulties in the combination between them. Herein, we proposed a new approach to enable the assisted metal ions to interact with MPc through fibrous support, constructing a novel bimetallic photocatalyst via simultaneously immobilizing iron(II) phthalocyanine (FePc) and Cu(II) onto the surface of amidoximated polyacrylonitrile (PAN) fiber. Taking the photodegradation of organic dyes as model reactions, this bimetallic catalyst achieves much higher photoactivity than that of the monometallic FePc catalyst, and effectively converts surface H₂O₂ into hydroxyl radicals rather than superoxide radicals and high-valent metal-oxo species. The Cu(II) not only enables the transfer of photoexcited electrons from FePc, but also promotes the running of Fe(II)/Fe(III) cycle to boost reactive radicals generation through H₂O₂ activation. The strategy of coupling Cu(II) with MPc through fibrous support provides a facile and promising solution for the advancement of MPc-based photocatalysis via visible light energy.

Facile synthesis of highly reactive and stable Fe-doped g-C3N4 composites for peroxymonosulfate activation: A novel nonradical oxidation process

Ferrous ions (Fe²⁺) are environmentally friendly materials but show extremely inefficient persulfate activation. Polymeric graphitic carbon nitride (g-C₃N₄) has recently shown potential to activate persulfates, but the process requires intense light irradiation. To overcome these drawbacks, we designed an innovative heterogeneous iron catalyst by doping Fe into g-C₃N₄ (Fe-g-C₃N₄) and used it to activate peroxymonosulfate (PMS) for degradation of pollutant phenol. The catalysts synthesized were fully characterized with various techniques, such as X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. Fe was found to be coordinated with the framework of g-C₃N₄. Approximately 100% degradation of phenol was achieved with Fe-g-C₃N₄ after 20 min of reaction, whereas less than 5% degradation of phenol was achieved with Fe²⁺. Fe-g-C₃N₄-PMS had a wide effective pH range, and its reactivity was nearly independent of natural illumination. In contrast to the previously proposed radical mechanisms, quenching experiments revealed that nonradical oxidation contributed to the observed degradation. The OO bond in the activated PMS likely underwent heterolysis, producing high-valence iron species (Fe^IVO) as the primary active species. These findings have important implications for the development of a selective heterogeneous nonradical-oxidation process.

Effects of Zirconium Doping Into a Monoclinic Scheelite BiVO4 Crystal on Its Structural, Photocatalytic, and Photoelectrochemical Properties

Effects of zirconium (Zr) doping into BiVO₄ powder on its structural properties and photocatalytic activity for O₂ evolution were examined. The formation of BiVO₄ powder crystallized in a monoclinic scheelite structure (ms-BiVO₄) was achieved when the sample was doped with a relatively small amount of Zr. The photocatalytic activity of Zr-doped ms-BiVO₄ powder was much higher than that of non-doped ms-BiVO₄. However, further doping caused a reduction of photocatalytic activity for O₂ evolution due to the occurrence of structural alterations into tetragonal scheelite and tetragonal zircon structures. Similar effects of Zr doping were also observed for the photoelectrochemical (PEC) system based on BiVO₄ thin films doped with various amounts of Zr. Thus, Zr doping was confirmed to be effective for improvements of photocatalytic and PEC functions of BiVO₄ for water oxidation.

Graphitic Carbon Nitride-Based Heterojunction Photoactive Nanocomposites: Applications and Mechanism Insight

The design of heterojunction with superior performance of light absorption and appropriate conduction band and valence band potentials is a promising approach for the applications in efficient environmental remediation and the solar energy storage. In recent years, many studies have been devoted to the applications of graphitic carbon nitride (g-C₃N₄)-based heterojunction photoactive nanomaterials under visible light irradiation due to its excellent physical, optical, and electrical properties, which inspired us to compile this review. Although many reviews demonstrated about the syntheses and applications of g-C₃N₄ composites, a targeted review on the systematic application and photocatalytic mechanisms of g-C₃N₄-based heterojunction, in which components are in intimate linkage with each other rather than a physical mixture, is still absent. In this review, the applications of g-C₃N₄-based heterojunction photoactive nanomaterials in environmental remediation and solar energy storage, such as photocatalytic treatment of persistent organic pollutants, heavy-metal-ion redox, oxidative decomposition of pathogens, water splitting for H₂ evolution, and CO₂ reduction, are systematically discussed. In addition, some emerging applications, such as solar cells and biosensors, are also introduced. Meanwhile, a comprehensive assessment on the basis of first-principles calculations and the thermodynamics and kinetics of surface catalytic reaction for the electronic structure and photocatalytic properties of g-C₃N₄-based heterojunction are valued by this review. In the end, a brief summary and perspectives in designing practical heterojunction photoactive nanomaterials also showed the bright future of g-C₃N₄-based heterojunction. Altogether, this review systematically complements the information that previous reviews have frequently ignored and points out the future development trends of g-C₃N₄-based heterojunction, which expected to provide important references and right directions for the development and practical applications of g-C₃N₄-based heterojunction photoactive nanomaterials.

Mimicking Natural Photosynthesis: Solar to Renewable H2 Fuel Synthesis by Z-Scheme Water Splitting Systems

Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called "Z-scheme" systems, which are inspired by the photosystem II-photosystem I (PSII/PSI) coupling from natural photosynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations. This is not only more efficient than using a single photocatalyst, but practically it could also be safer. Researchers within the field are constantly aiming to bring systems toward industrial level efficiencies by maximizing light absorption of the materials, engineering more stable redox couples, and also searching for new hydrogen and oxygen evolution cocatalysts. This review provides an in-depth survey of relevant Z-schemes from past to present, with particular focus on mechanistic breakthroughs, and highlights current state of the art systems which are at the forefront of the field.

Visible-Light-Driven Chemoselective Hydrogenation of Nitroarenes to Anilines in Water through Graphitic Carbon Nitride Metal-Free Photocatalysis

Green and efficient procedures are essential for the chemoselective hydrogenation of functionalized nitroarenes to form industrially important anilines. Herein, it is shown that visible-light-driven, chemoselective hydrogenation of functionalized nitroarenes with groups sensitive to forming anilines can be achieved in good to excellent yields (82-100 %) in water under relatively mild conditions and catalyzed by low-cost and recyclable graphitic carbon nitride. The process is also applicable to gram-scale reaction, with a yield of aniline of 86 %. A study of the mechanism reveals that visible-light-induced electrons are responsible for the hydrogenation reactions, and thermal energy can also promote the photocatalytic activity. A study of the kinetics shows that this reaction possibly occurs through one-step hydrogenation or stepwise condensation routes. A wide range of applications can be expected for this green, efficient, and highly selective photocatalysis system in reduction reactions for the synthesis of fine chemicals.

Carbon-Dot-Decorated TiO2 Nanotubes toward Photodynamic Therapy Based on Water-Splitting Mechanism

The use of visible light to produce reactive oxygen species (ROS) from renewable water splitting is a highly promising means in photodynamic therapy (PDT). Up to date, diverse inorganic-organic hybrid materials developed as photosensitizers still undergo low therapeutic efficiency and/or poor stability. Herein, a kind of carbon-nanodot-decorated TiO₂ nanotubes (CDots/TiO₂ NTs) composite is developed and applied for photodynamic therapy. Upon 650 nm laser light excitation, the emissions with short wavelengths (325-425 nm) from the CDots as a result of upconversion process excite TiO₂ NTs to form electron/hole (e^- /h⁺ ) pairs, triggering the reaction with the adsorbed oxidants to produce ROS. Moreover, the CDots deposited on the surface of TiO₂ NTs markedly enhance the light absorption response and narrow the band gap compared with anatase TiO₂ nanoparticles, thereby increasing the photosensitizing efficiency. Besides, the CDots show high chemical catalytic activity for H₂ O₂ decomposition even if no light is needed, which is essential for PDT. The excellent therapeutic performance actuated by 650 nm light is demonstrated by in vitro and in vivo assays. This photosensitizer comprises low-cost, earth-abundant, environment-friendly merits, and especially excellent stability, implying its feasible application in biomedical field.

Polymeric carbon nitride for solar hydrogen production

If solar hydrogen production from water is to be a realistic candidate for industrial hydrogen production, the development of photocatalysts, which avoid the use of expensive and/or toxic elements is highly desirable from a scalability, cost and environmental perspective. Metal-free polymeric carbon nitride is an attractive material that can absorb visible light and produce hydrogen from water. This article reviews recent developments in polymeric carbon nitride as used in photocatalysis and then develops the discussion focusing on the three primary processes of a photocatalytic reaction: light-harvesting, carrier generation/separation/transportation and surface reactions.

Photochemical CO2 reduction using structurally controlled g-C3N4

Graphitic carbon nitride (g-C₃N₄) synthesised from a urea precursor is an excellent CO₂ reduction photocatalyst using [Co(bpy)_n]²⁺ as a co-catalyst. A five-fold increase in activity for the highly polymerised urea derived g-C₃N₄ is achieved compared to alternative precursors. Transient absorption, time-resolved and steady-state emission studies indicate that the enhanced activity is related to both an increased driving force for photoelectron transfer and a greater availability of photogenerated charges.

Z-Scheme Photocatalytic Water Splitting on a 2D Heterostructure of Black Phosphorus/Bismuth Vanadate Using Visible Light

Spontaneously solar-driven water splitting to produce H₂ and O₂ , that is, the conversion of solar energy to chemical energy is a dream of mankind. However, it is difficult to make overall water splitting feasible without using any sacrificial agents and external bias. Drawing inspiration from nature, a new artificial Z-scheme photocatalytic system has been designed herein based on the two-dimensional (2D) heterostructure of black phosphorus (BP)/bismuth vanadate (BiVO₄ ). An effective charge separation makes possible the reduction and oxidation of water on BP and BiVO₄ , respectively. The optimum H₂ and O₂ production rates on BP/BiVO₄ were approximately 160 and 102 μmol g^-1  h^-1 under irradiation of light with a wavelength longer than 420 nm, without using any sacrificial agents or external bias.

Construction of a Z-scheme core–shell g-C3N4/MCNTs/BiOI nanocomposite semiconductor with enhanced visible-light photocatalytic activity

An S–C–S Z-scheme core–shell g-C₃N₄/MCNTs/BiOI nanocomposite semiconductor with enhanced photocatalytic activity was designed and fabricated.

Fabrication of TiO2 on porous g-C3N4 by ALD for improved solar-driven hydrogen evolution

Porous graphitic carbon nitride (P-g-C₃N₄) thin sheets were fabricated by a one-step calcination of a mixture of urea, melamine, and ammonia chloride at 550 °C. P-g-C₃N₄ showed 48% higher photocatalytic H₂ production from methanol aqueous solution than conventional urea-derived graphitic carbon nitride (g-C₃N₄) because the existence of numerous pores reduces the recombination rate of charge carriers. In order to further enhance the photocatalytic activity, TiO₂ was uniformly deposited on P-g-C₃N₄ by 60–300 cycles of atomic layer deposition (ALD) to form the TiO₂@P-g-C₃N₄ composite. They exhibited much higher photocatalytic hydrogen production rates than both TiO₂ and P-g-C₃N₄. Among all composites, the sample deposited with 180 ALD cycles of TiO₂ showed the highest H₂ production because of optimal diffusion length for electrons and holes. It also performed better than the sample of g-C₃N₄ deposited with 180 cycles of TiO₂.

Schematic of Pt-loaded TiO₂@P-g-C₃N₄ 2D/2D heterojunction structure and the proposed mechanism of charge transfer for photocatalytic H₂ evolution.

Electrocatalytic and photocatalytic hydrogen evolution integrated with organic oxidation

We have summarized the recent progress in electrocatalytic and photocatalytic water splitting integrated with organic oxidation for efficient H₂ generation, which features no formation of explosive H₂/O₂ mixtures and reactive oxygen species, higher efficiency compared to conventional water splitting and potential co-production of value-added organic products.

Facile fabrication of direct solid-state Z-scheme g-C3N4/Fe2O3 heterojunction: a cost-effective photocatalyst with high efficiency for the degradation of aqueous organic pollutants

In situ synthesis of a cost-effective g-C₃N₄/Fe₂O₃ hybrid with enhanced photocatalytic activity for the degradation of organic pollutants based on the direct Z-scheme mechanism.

Supported ZnBr2 and carbon nitride bifunctional complex catalysts for the efficient cycloaddition of CO2 with diglycidyl ethers

Bifunctional catalysts with large surface areas performed well in the cycloaddition of CO₂ and bisepoxides under solvent and co-catalyst free conditions.

Efficient spatial charge separation and transfer in ultrathin g-C3N4 nanosheets modified with Cu2MoS4 as a noble metal-free co-catalyst for superior visible light-driven photocatalytic water splitting

Cu₂MoS₄ was employed as a promising non-noble metal co-catalyst to couple with g-C₃N₄ for highly efficient water splitting.