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Photocatalysis can create a green way to produce clean energy resources, degrade pollutants and achieve carbon neutrality, making the construction of efficient photocatalysts significant in solving environmental issues. Conjugated polymers (CPs) with adjustable band structures have superior light‐absorption capacity and flexible morphology that facilitate contact with other components to form advanced heterojunctions. Interface engineering can strengthen the interfacial contact between the components and further enlarge the interfacial contact area, enhance light absorption, accelerate charge transfer and improve the reusability of the composites. In order to throw some new light on heterojunction interface regulation at a molecular level, herein we summarize CP‐based composites with improved photocatalytic performance according to the types of interactions (covalent bonding, hydrogen bonding, electrostatic interactions, π‐π stacking, and other polar interactions) between the components and introduce the corresponding interface building methods, identifying techniques. Then the roles of interfaces in different photocatalytic applications are discussed. Finally, we sum up the existing problems in interface engineering of CP‐based composites and look forward to the possible solutions. [ABSTRACT FROM AUTHOR]

Improving the insufficient carrier separation dynamics is still of significance in carbon nitride (C3N4) research. Extensive research has been devoted to improving the carrier separation efficiency through a single strategy, while ignoring the synergistic enhancement effect produced by coupling two or more conventional strategies. Herein, we reported the fabrication of cyano group‐containing Fe‐doped C3N4 porous materials via direct co‐calcination of iron acetylacetonate and melamine for synergistically improving the photocatalytic performance. Iron acetylacetonate can promote the generation of cyano groups and form Fe‐doping in C3N4, thereby increasing the visible‐light absorption and reactive sites. Further, the internal donor‐acceptor system formed by cyano groups and Fe‐doped sites promoted charge carrier separation and inhibited the radiation recombination of e−‐h+ pairs. The optimized photocatalytic activity of Fe−CN‐2 sample was 4.5 times of bulk C3N4 (BCN). [ABSTRACT FROM AUTHOR]

Over the past few decades, rising global concentrations of carbon dioxide (CO2) produced from excessive consumption of fossil fuels have become the main cause of the greenhouse effect around the world. Converting CO2 into solar fuel through photocatalysis is an effective solution to mitigate the greenhouse effect and energy crisis simultaneously. Increasingly attention has been paid on bismuth‐based photocatalytic CO2 reduction owing to the unique electronic structure of bismuth‐based photocatalysts. In recent years, researchers have made many breakthroughs in the bismuth‐based photocatalytic reduction of carbon dioxide. In this review, we summarize the structure of common bismuth‐based photocatalysts and focus on the recent progress of rational approach for optimizing catalysts loading, including morphology design, component regulation, facet engineering, doping, and defects engineering on the single bismuth‐based photocatalytic system, cocatalyst loading, heterojunction construction, localized surface plasmon resonance, and polarization. Finally, perspectives and opportunities are presented for future trends of CO2 photocatalytic conversion. [ABSTRACT FROM AUTHOR]

Photocatalysis via direct solar‐to‐chemical energy conversion is an intriguing approach for alleviating the pressure of high energy consumption caused by social development. However, photocatalytic efficiency is greatly restricted by unsatisfactory light‐harvesting capacity, high carrier recombination rates, and sluggish reaction kinetics. Indeed, vacancy engineering is an attractive strategy to regulate photocatalytic reaction performance to maximize the utilization and storage of solar energy. In this review, we summarize recent progress about the important roles of vacancy defects on solar‐driven photocatalytic applications. The current advanced characterization techniques, especially for in situ/operando techniques, are first presented for elucidating the structure‐performance relationships of defective semiconductors in photocatalysis. Subsequently, the crucial roles of vacancies in enhancing photocatalytic performance are highlighted from three important processes: light absorption, carrier separation and migration, and surface reaction. Finally, based on the above understanding, perspectives and opportunities about defective materials are considered for various photocatalytic applications. [ABSTRACT FROM AUTHOR]

Direct conversion of solar light into chemical energy by means of photocatalysis or photoelectrocatalysis is currently a point of focus for sustainable energy development and environmental remediation. However, its current efficiency is still far from satisfying, suffering especially from severe charge recombination. To solve this problem, the piezo‐phototronic effect has emerged as one of the most effective strategies for photo(electro)catalysis. Through the integration of piezoelectricity, photoexcitation, and semiconductor properties, the built‐in electric field by mechanical stimulation induced polarization can serve as a flexible autovalve to modulate the charge‐transfer pathway and facilitate carrier separation both in the bulk phase and at the surfaces of semiconductors. This review focuses on illustrating the trends and impacts of research based on piezo‐enhanced photocatalytic reactions. The fundamental mechanisms of piezo‐phototronics modulated band bending and charge migration are highlighted. Through comparing and classifying different categories of piezo‐photocatalysts (like the typical ZnO, MoS2, and BaTiO3), the recent advances in polarization‐promoted photo(electro)catalytic processes involving water splitting and pollutant degradation are overviewed. Meanwhile the optimization methods to promote their catalytic activities are described. Finally, the outlook for future development of polarization‐enhanced strategies is presented. [ABSTRACT FROM AUTHOR]

Z-scheme composite represents an ideal system for photocatalytic hydrogen evolution, but the charge transfer mechanism is still ambiguous, and how to design and construct such system is a big challenge. Herein, we demonstrate that C 3 N 4 -W 18 O 49 , the type-II composite, can be switched to direct Z-scheme via modulating the interfacial band bending. Experiment and DFT computation results reveal that the adsorption of triethanolamine (TEOA) on C 3 N 4 surface significantly uplifts its Femi level, inverses the continuous interfacial band bending to interrupted one, and thus switches the composite from type-II to Z-scheme, without the assistance of any electron shuttles. Importantly, this Z-scheme C 3 N 4 /W 18 O 49 composites exhibit much better photocatalytic H 2 activity compared with pure C 3 N 4 , and obtain H 2 evolution rate of 8597 μmol h −1 g −1 (AQY of 39.1% at 420 nm) with Pt as cocatalyst and TEOA as hole scavenger. Also, using this hypothesis we successfully explain why C 3 N 4 /WO 3 is inherent Z-scheme composite but the performance is not as good as C 3 N 4 /W 18 O 49 and why TEOA is the best hole scavenger for C 3 N 4 . This work is expected to give deep insights into understanding the charge transfer in semiconductor composites and rationally designing and constructing Z-scheme photocatalyst for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Conjugated polymers, covalent bonding, heterojunctions, interface engineering, noncovalent interactions Frontispiece: Interface Engineering of Conjugated Polymer-Based Composites for Photocatalysis Keywords: conjugated polymers; covalent bonding; heterojunctions; interface engineering; noncovalent interactions EN conjugated polymers covalent bonding heterojunctions interface engineering noncovalent interactions 1 1 1 12/29/22 20221227 NES 221227 B Interface engineering b can facilitate the self-assembly of conjugated polymer-based composites through a series of intermolecular interactions (covalent bonding, hydrogen bonding, dipole-dipole interactions, electrostatic interactions, and - stacking) between the components, further improving the photocatalysis process, which depends heavily on smooth charge transfer at the well-formed interface. [Extracted from the article]

Efficient charge separation and broaden light absorption are of crucial importance for solar-driven hydrogen evolution reaction (HER), and graphitic carbon nitride (g-C 3 N 4 ) is a very promising photocatalyst for this reaction. Here we report a facile precursor pre-treatment method, by forming hydrogen bond-induced supramolecular aggregates, to fabricate g-C 3 N 4 with simultaneous novel porous network and controllable O-doping. Experimental and DFT computation identified that O doping preferentially occurs on two-coordinated N position, and the porous network and O-doping synergetically promote the light harvesting and charge separation. As a result, this material shows 6.1 and 3.1 times higher HER activity (with apparent quantum efficiency of 7.8% at 420 nm) than bulk and even 3D porous g-C 3 N 4 . This work highlights that simply pre-treating the precursor can not only control the architecture but also introduce helpful foreign atoms or monomer in the matrix, which provides a useful strategy to design and fabricate highly efficient g-C 3 N 4 photocatalyst. [ABSTRACT FROM AUTHOR]

Abundant Zn vacancies (7.5 mol%) were successfully introduced into undoped ZnO by a simple solvothermal method followed with thermal calcination, and undoubtedly proved by both characterizations and computations. The presence of Zn vacancies led to some new properties in ZnO, such as p-type conductivity, room-temperature ferromagnetism and high photocatalytic activity. The formation process of abundant Zn vacancies during the synthesis of ZnO was also discussed. This work demonstrates that metal defects can be easily engineered in undoped metal oxides, which may trigger many unexpected behaviors and thus widen the synthetic approach and application of functional materials in energy fields. [ABSTRACT FROM AUTHOR]

Highlights: [•] W18O49/TiO2 hybrid achieves significant synergetic promotion on the photoactivity and photostability. [•] W18O49(10wt%)/TiO2 and W18O49(90wt%)/TiO2 show 2.43 (2.64) and 1.31 (1.52) times higher activity than the calculated baseline in degradation of MO (phenol), under UV–vis and visible light, respectively. [•] Well-matched band structure between W18O49 and TiO2 enhances the photo-induced charge separation and transfer. [•] ·O2 − and hole, especially the former, are the active species involved in the photodegradation. [ABSTRACT FROM AUTHOR]

Abstract: The photoisomerization of norbornadiene using M–Ti–MCM-41 (M=V, Fe and Cr) has been studied to develop an alternative for solar energy accumulation and high energy aerospace fuel synthesis. The photocatalysts were prepared via hydrothermal method and characterized by EDX, XRD, N2 adsorption–desorption, TEM, UV–vis, XPS and IR. With the same Si/M ratio in starting materials, the final concentration of V in the photocatalyst is significantly lower than that of Fe and Cr. V5+ and Fe3+ ions are highly dispersed in Si–O framework with tetrahedral coordination when the metal content is low, and the ordered structure is well retained. However, some species in higher coordination and polymerized environments present with increasing metal content, and the ordered structure becomes to collapse. Cr ions are difficult to get into the framework with various species like extraframework Cr6+ and bulk Cr2O3 formed, also the ordered structure is greatly destroyed. Under UV irradiation, the transition metal ions can improve the photoisomerization activity, with the order of V>Fe>Cr. The activities of V– and Fe–Ti–MCM-41 rise with the increase of Si/M ratio, whereas the performance of Cr–Ti–MCM-41 is irregular. The photocatalysts do not exhibit any activity under visible light, regardless of their absorption in visible-light region. The activity is closely related to the extent of dispersion and local structure of metal ions, about which an indirect excitation process of Ti–O species is suggested. [Copyright &y& Elsevier]

Abstract: A glow discharge plasma treatment was used to modify the impregnation method to prepare photocatalysts with the following steps: impregnation, cold plasma treatment, calcination, and reduction. The activity and properties of the catalysts were studied in comparison with those prepared with traditional impregnation method. The activities for hydrogen generation from water/alcohols mixtures were significantly promoted. The properties including the metal dispersion, near-UV absorption, and metal stability were also enhanced. The enhanced metal dispersion and optical absorption partly promoted the activity but the effect was limited. It was speculated that the plasma method produced an enhanced metal–support interaction. According to high-resolution TEM observation, a greatly distorted metal–support interface was formed on the plasma prepared catalyst. This interface allowed a close contact between the metal atoms and support lattices, which supported the existence of the enhanced interaction. This interface was expected to facilitate the electron transfer during photocatalytic reaction and be the major reason for the high activity of the plasma prepared photocatalysts. [Copyright &y& Elsevier]

V-doped TiO2 quantum dots (QDs) possessing many Ti3+ defects were fabricated by simple hydrolysis using MCM-41 as a support. The QDs show high charge-separation efficiency and high photocatalytic activity due to the quantum size effect and the newly formed defect- and dopant-mediated band levels. [ABSTRACT FROM AUTHOR]

Solar‐driven water splitting is in urgent need for sustainable energy research, for which accelerating oxygen evolution kinetics along with charge migration is the key issue. Herein, Mn3+ within π‐conjugated carbon nitride (C3N4) in form of Mn–N–C motifs is coordinated. The spin state (eg orbital filling) of Mn centers is regulated by controlling the bond strength of Mn–N. It is demonstrated that Mn serves as intrinsic oxygen evolution reaction (OER) site and the kinetics is dependent on its spin state with an optimized eg occupancy of ≈0.95. Specifically, the governing role of eg occupancy originates from the varied binding strength between Mn and OER intermediates. Benefiting from the rapid spin state‐mediated OER kinetics, as well as extended optical absorption (to 600 nm) and accelerated charge separation by intercalated metal‐to‐ligand state, Mn–C3N4 stoichiometrically splits pure water with H2 production rate up to 695.1 µmol g−1 h−1 under simulated sunlight irradiation (AM1.5), and achieves an apparent quantum efficiency of 4.0% at 420 nm, superior to most solid‐state based photocatalysts to date. This work for the first time correlates photocatalytic redox kinetics with the spin state of active sites, and suggests a nexus between photocatalysis and spin theory. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting is promising for hydrogen energy production using solar energy and developing highly efficient photocatalysts is challenging. Defect engineering is proved to be a very useful strategy to promote the photocatalytic performance of metal‐based photocatalysts, however, the vital role of defects is still ambiguous. This work comprehensively reviews point defective metal‐based photocatalysts for water splitting, focusing on understanding the defects' disorder effect on optical adsorption, charge separation and migration, and surface reaction. The controllable synthesis and tuning strategies of defective structure to improve the photocatalytic performance are summarized, then the characterization techniques and density functional theory calculations are discussed to unveil the defect structure, and analyze the defects induced electronic structure change of catalysts and its ultimate effect on the photocatalytic activity at the molecular level. Finally, the challenge in developing more efficient defective metal‐based photocatalysts is outlined. This work may help further the understanding of the fundamental role of defect structure in the photocatalytic reaction process and guide the rational design and fabrication of highly efficient and low‐cost photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A two-step cystine-mediated strategy is developed to alter the symmetry structure of C 3 N 4. • CN-25CYS possesses alkyl groups and nitrogen vacancies. • The distorted arrangements activate n-π* electron transition of carbon nitride. • The spatial separation of oxidation and reduction sites promotes charge separation. • CN-25CYS achieves 9.6-fold and 15.6-fold higher H 2 production rates and RhB degradation rates. The periodical distribution of N and C atoms in the carbon nitride skeleton results in intrinsically insufficient light absorption and serious carrier recombination. Herein, an efficient two-step cystine-mediated strategy was developed to alter the structure symmetry of C 3 N 4 via the introduction of alkyl groups and nitrogen vacancies. The experimental analysis and theoretical calculation confirm that the formation of alkyl groups and nitrogen vacancies can modulate band structure and activate n-π* electron transition. Especially, the charge density in CN-25CYS is redistributed with spatial separation of oxidation and reduction sites, suppressing photogenerated charge recombination effectively. Therefore, the distorted carbon nitride (CN-25CYS) exhibits 9.6-times and 15.6-times higher photoreaction rates in hydrogen production and RhB degradation than the pristine one (CN-0CYS), respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective TEB-DBT CMPs with alkynyl defects via the molecular design are constructed. • Combination of the DFT calculations and experimental results, the incorporation of alkynyl defect accelerates the separation of photogenerated charge carriers. • The microstructure, band structure, and photocatalytic performance of CMPs can be regulated by varying the content of alkynyl defect. Defect engineering is a versatile approach to modulate band and electronic structures as well as materials performance. Nowadays, more research has been performed for enhancing catalytic performance of organic photocatalysts via the regulation of structure defect. Herein, we constructed the dibenzo[b,d]thiophene-sulfone-based conjugated microporous polymers (CMPs) with alkynyl defects via the molecular design. The effects of the concentration of alkynyl defects on the optical band gap, energy level structure, charge separation and photoactivity of the as-prepared samples were further explored. Combination of the first-principle density functional theory (DFT) calculations and experimental results, the incorporation of alkynyl defects accelerated the separation of photogenerated charge carriers. Furthermore, the concentration of alkynyl defects in CMPs can be adjusted by the dosage of 1,3-diethynylbenzene (MEB), thereby modulating the electronic structure and charge carrier separation properties. At appropriate alkynyl defect concentration, the prepared Defect-TD-2 shows higher visible-light photocatalytic performance for H 2 production and pollutants degradation. The work therefore shows an efficient self-modification strategy for improving the photoactivity of CMPs. [ABSTRACT FROM AUTHOR]

Ag 2 O/P25 and Ag/P25 catalysts were synthesized and applied in the photocatalytic reduction of nitrate with formic acid as a hole scavenger. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) analysis demonstrate that Ag 2 O or Ag nanoparticles were well distributed on the surface of P25. Under UV irradiation, 5% Ag 2 O/P25 showed a fast rate (0.95 h −1 , 6.3 times of P25), a high conversion (97.2%, 3.63 times of P25) and a high N 2 selectivity (83.1%, 1.15 times of P25) for nitrate reduction. The improved separation of electron–hole pairs on Ag 2 O/P25 results in the high conversion of nitrate. Moreover, compared with the Ag/P25 catalyst, Ag 2 O/P25 exhibited a good reusability in nitrate reduction. The formed Ag–Ag 2 O structure [Ag(0) present on the surface of Ag 2 O] over P25 by partial photoreduction of deposited Ag 2 O contributed to the better stability of Ag 2 O/P25 in nitrate reduction. The present study provides a new sight into the use of Ag 2 O/P25 catalyst in the reduction of nitrate. [ABSTRACT FROM AUTHOR]

The work function of BiVO 4 is modulated from smaller to larger than that of PCN by controlling the oxygen vacancy, which switches the direction of interfacial band bending in BiVO 4 /PCN heterojunction. Accordingly, the photoinduced charge transfer mechanism is changed from type-II to direct Z-scheme for superior solar-driven pure water splitting. [Display omitted] Nature-inspired artificial Z-scheme photocatalyst offers great promise in solar overall water splitting, but its rational design, construction and interfacial charge transfer mechanism remain ambiguous. Here, we design an approach of engineering interfacial band bending via work function regulation, which realizes directional charge transfer at interface and affords direct Z-scheme pathway. Taking BiVO 4 as prototype, its oxygen vacancy concentration is reduced by slowing down the crystallization rate, thereby changing the work function from smaller to larger than that of polymeric carbon nitride (PCN). Consequently, the photoinduced charge transfer pathway of BiVO 4 /PCN is switched from type-II to Z-scheme as evidenced by synchronous illuminated X-ray photoelectron spectroscopy (XPS) and femtosecond transient absorption spectroscopy. Specifically, the direct Z-scheme BiVO 4 /PCN shows superior photocatalytic performance in water splitting. This work provides deep insights and guidelines to constructing heterojunction photocatalysts for solar utilization. [ABSTRACT FROM AUTHOR]

Improving the insufficient carrier separation dynamics is still of significance in carbon nitride (C3N4) research. Extensive research has been devoted to improving the carrier separation efficiency through a single strategy, while ignoring the synergistic enhancement effect produced by coupling two or more conventional strategies. Herein, we reported the fabrication of cyano group‐containing Fe‐doped C3N4 porous materials via direct co‐calcination of iron acetylacetonate and melamine for synergistically improving the photocatalytic performance. Iron acetylacetonate can promote the generation of cyano groups and form Fe‐doping in C3N4, thereby increasing the visible‐light absorption and reactive sites. Further, the internal donor‐acceptor system formed by cyano groups and Fe‐doped sites promoted charge carrier separation and inhibited the radiation recombination of e−‐h+ pairs. The optimized photocatalytic activity of Fe−CN‐2 sample was 4.5 times of bulk C3N4 (BCN). [ABSTRACT FROM AUTHOR]

ZnO p-n homojunctions with tunable p/n ratio was fabricated by decorating n-ZnO nanoparticles on p-ZnO leaves and shows excellent performance in charge separation and photocatalysis. • ZnO p-n homojunction was fabricated by decorating n-type ZnO NPs on p-type ZnO. • ZnO p-n homojunction is abundant in both V o and V Zn simultaneously. • The p-n homojunction shows high efficiency in charge transfer and separation. • ZPN-5 with suitable p/n ratio shows the highest photocatalytic and PEC performance. Construction of junctions between semiconductors is an effective way to promote charge separation and thus improve the photoelectrochemical and photocatalytic performance. Specifically, p-n homojunctions are more efficient due to the larger driving force and lower transfer barrier over the interface. Herein, we fabricated ZnO p-n homojunctions by depositing n-type ZnO nanoparticles (with oxygen vacancy) on the surface of p-type ZnO (with metal vacancy). The structures of the composite were well characterized by TEM, XRD, TG, XPS and EPR analyses. Meanwhile, both the "V-shaped" Mott-Schottky plots and anodic shift of onset potentials confirmed the existence of p-n homojunction, which exhibits much more efficient charge transfer and separation than pure type ZnO as indicated by PL and EIS measurements. As a result, p-n homojunction exhibited activity of 3.2-fold and 3.3-fold higher than pure p-ZnO in photodegradation of phenol and as photocathode in photoelectrochemical water splitting, respectively. This work provides a new strategy for the design and fabrication of highly efficient photocatalysts with promoted charge separation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pt decorated Ni(OH) 2 composite is highly effective in activating and cleaving H 2 O. • The composite is in-situ grown on semiconductors via photoinduced deposition. • Pt/Ni(OH) 2 -C 3 N 4 achieves an AQE of 1.8% at 420 nm in overall water splitting. • Pt/Ni(OH) 2 enables TiO 2 to split pure water. Abstract Photocatalytic overall water splitting is one of the ultimate goals in solar conversion and the activation and cleavage of H 2 O molecule is the initial and often rate-determining step in this reaction. Through DFT calculations, we designed Pt cluster decorated Ni(OH) 2 nanoparticles (Pt/Ni(OH) 2) as robust cocatalyst capable of activating H 2 O and dissociating HO H bonds. Then the unique structure was fabricated through in-situ photo-oxidation of Ni 2 P to Ni(OH) 2 on semiconductor like C 3 N 4 and subsequent selective photo-deposition of Pt on Ni(OH) 2 surface. Pt/Ni(OH) 2 -C 3 N 4 is much more active in photocatalytic HER, OER and overall water splitting compared with Pt, Ni(OH) 2 and spatially separated co-loaded Ni(OH) 2 -Pt on C 3 N 4. And Pt/Ni(OH) 2 -C 3 N 4 achieves an AQE of 1.8% at 420 nm in overall water splitting by using only 0.3 wt% Pt, superior to most solid-state photocatalytic systems to date. Moreover, Pt/Ni(OH) 2 composite enables TiO 2 to split pure water in good stoichiometry. This work emphasizes the importance of H 2 O activation and may pave the way for enabling single semiconductors to efficiently split pure water. [ABSTRACT FROM AUTHOR]

Photocatalytic water oxidation suffers from sluggish kinetics and remains the bottleneck for water splitting. Here, using CeO 2 nanorods as model photocatalyst we studied the critical role of oxygen vacancies in photocatalytic water oxidation. First CeO 2 nanorods with similar morphology but different concentration of oxygen vacancies were fabricated by one-step hydrothermal method with in-situ reducing treatment. The optical absorption, charge transfer efficiency, and photocatalytic activity in oxygen generation were found closely dependent on the concentration of oxygen vacancies. Then density functional theory calculations were conducted to unveil the role of oxygen vacancies and understand the water oxidation mechanism. It was found the presence of oxygen vacancies narrows the bandgap and modulates the electronic structure for accelerating the charge transfer, in good agreement with the experimental observations. The overall oxygen generation pathway was screened and the oxygen vacancies were found to lower the barrier energy for the rate limiting step of O O bond formation and restrain the reverse reaction of O and H, thus the O 2 generation kinetics on oxygen-defective CeO 2 are improved significantly. This study provides in-depth understanding on the critical role of oxygen vacancies in photocatalytic water oxidation and is helpful for designing highly efficient photocatalyst to overcome the bottleneck of water splitting. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4 ) has emerged as a promising photocatalyst, but poor charge separation and low surface area limit its activity. Here, we report a hydrothermal method to generate hydrogen bonded supramolecular complex via water-based homogeneous supramolecular assembly, which is a promising precursor to fabricate porous and oxygen-doped g-C 3 N 4 . The hydrothermal treatment provides a homogeneous environment for hydrolysis of melamine to produce cyanuric acid and reaction of cyanuric acid with remained melamine to create the in-plane ordering and hydrogen bonded supramolecular complex. The complex can template uniform nanoporous structure and also provide an opportunity for O-doping in the g-C 3 N 4 network upon calcination in air. The resulted g-C 3 N 4 (GCN-4) possesses high surface area, well-defined 3D morphology and oxygen-dopant in the lattice. Subsequently, the visible light absorption, charge separation, and wettability are considerably enhanced. This catalyst exhibits higher hydrogen evolution rate by 11.3 times than the bulk g-C 3 N 4 under visible light irradiation, with apparent quantum efficiency of 10.3% at 420 nm. [ABSTRACT FROM AUTHOR]

ZnO is an important semiconductor and has been widely used in the field of photocatalysis, solar cell and environmental remediation. Herein, we fabricated C-doped ZnO ball-in-ball hollow microspheres (BHMs) by a facile solvothermal treatment of zinc acetate in ethylene glycol-ethanol mixture. The presence of ethylene glycol (EG) leads to the formation of initial single-layered hollow spheres and then a time-dependent evolution transforms them into uniform BHMs with tunable shell thickness and void space. XPS characterizations reveal that C-dopants are introduced into the lattice of ZnO BHMs, with its concentration increasing with solvothermal time and then becoming saturated in 12 h. ZEG-12 (ZnO BHMs with 12-h solvothermal treatment), with an optimal hollow structure and C-doping concentration, performs the best optical absorption capability, efficiency of charge separation and transfer, and mass transfer in reaction media, as proved by SEM, TEM, PL, BET and EIS characterizations. When applied as photocatalyst for organic-pollutant degradation and as photoanode material for PEC water splitting, ZEG-12 exhibits respectively ca. 8.9-fold and 10.5-fold higher activity than pristine ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

Direct Z-scheme photocatalyst, which enables efficient charge separation and retains high redox ability, is promising material for visible-light-driven hydrogen evolution. Here we developed a one-step solvothermal method to fabricate direct Z-scheme CdS/CdWO 4 composite via treating W 18 O 49 with CH 3 CSNH 2 and Cd(CH 3 COO) 2 . By controlling the dosage of Cd(CH 3 COO) 2 , CdS nanoparticles decorated CdWO 4 nanowires (CS-2) is synthesized. UV–vis DRS and XPS spectra demonstrate that the CdWO 4 possesses a large amount of oxygen vacancies, which help to form ohmic contact and broaden light absorption. Compared with CdS, CS-2 Exhibits 18 times higher visible-light H 2 evolution activity using lactic acid as sacrificial agent and shows 7.8-fold higher photocurrent density. Moreover, photoelectrochemical test manifests the efficient separation of the photo-induced charge carriers. Radical-trapping experiments along with in-situ Pt photodeposition further prove that the charge transfer and separation follows Z-scheme mechanism. This work highlights the critical role of defects in the formation of direct Z-scheme composite. [ABSTRACT FROM AUTHOR]

ZnO is an important semiconductor that has been widely applied in solar cell, photocatalysis, environmental remediation. Doping and morphology control are important approaches to improve its photocatalytic performance. Herein, a facile two-step calcination method was developed to fabricate carbon(C)-doped cubic ZnO with porous structure from zeolite imidazolate frameworks (ZIF-8). Compared with one-step pyrolysis, the approach of two-step calcination not only retains the cubic morphology with inter-connected ZnO nanoparticles and porous structure but also introduces C doping in ZnO lattice effectively. This morphology has advantage in charge transfer, optical absorption and mass transfer during the photoreaction, and C doping results in high charge-separation efficiency. The sample C350-400 (C-doped ZnO, firstly calcined at 350 °C for 2 h from ZIF-8, then 400 °C for 1 h) shows the maximum photoactivity, which is ca . 3-fold and 4-fold higher than ZnO (C450) in photodegradation and PEC water splitting (under UV–vis irradiation), respectively. It is expected that the preparation of metal oxide from MOF is a very promising way to fabricate highly efficient photocatalyst. [ABSTRACT FROM AUTHOR]

TiO 2 has been intensively investigated for decades as the most important photocatalyst, but its photoactivity still needs further improvment. TiO 2 surface and interface are vital in photocatalysis because it is where the photo-excitation, charge transfer and subsequent photoreaction take place. Surface and interface control has been demonstrated as very effective approach to synthesize highly efficient TiO 2 . Here we highlight our recent work as well as the state-of-the-art in controlling of TiO 2 surface and interface including facet growth, surface decoration and surface adsorption that leads to better photocatalytic performance. It is expected to provide some guidelines for rational design and fabrication of highly efficient TiO 2 -based materials for photocatalysis. [ABSTRACT FROM AUTHOR]

Composites having both maximized adsorption capability and high photocatalytic activity are very promising for pollutant removal by combining adsorption and photocatalysis. In this work, we report a facile sonochemical synthesis of Cu 2 O(nanoparticles)/Cu 2 (OH) 3 NO 3 (sheets) composites with tunable composition using only copper powders and Cu(NO 3 ) 2 as precursors. The composites can be controlled from almost pure Cu 2 O (98.1%) to pure Cu 2 (OH) 3 NO 3 (95.9%) through adjusting the initial ratio of Cu 2+ :Cu 0 and sonication time. Controlled experiments show that Cu 2 O nanoparticles are formed first via the redox reaction between Cu 2+ and Cu 0 , after that Cu 2 O are converted to Cu 2 (OH) 3 NO 3 . Cu 2 (OH) 3 NO 3 synthesized using the sonochemical method exhibits outstanding adsorption capability toward organic dyes, subsequently Cu 2 O can degrade them quickly via photocatalysis, so the Cu 2 O/Cu 2 (OH) 3 NO 3 composites are very efficient to remove pollutant due to the synergetic effect of adsorption and photocatalysis. In particular, composite with 30.6% of Cu 2 (OH) 3 NO 3 and 69.4% of Cu 2 O shows the highest removal capability and good stability. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation of organic pollutants attracts much attention in environment remediation, and it is still a challenge to develop highly efficient and stable visible-light-response photocatalyst. Herein, we synthesized Ag 3 PO 4 /TiO 2 (P-25) composite via a facile in situ precipitation method to enhance the activity and stability of Ag 3 PO 4 . SEM and TEM characterizations indicate TiO 2 particles are dispersed on Ag 3 PO 4 surface, resulting in heterojunction interfaces. UV–vis DRS spectra show that TiO 2 in the composite does not interfere the absorption of visible light, while the photoluminescence spectra confirm TiO 2 inhibits the recombination of photo-induced charges. Therefore, during the photodegradation of organic pollutants under visible light, the composites are much more active than pure Ag 3 PO 4 . Moreover, XPS and XRD analysis show the reduction of Ag 3 PO 4 to Ag 0 is retarded during the photoreaction. Furthermore, the effect of TiO 2 amount in the composites was studied, and AP12 is the most active with the reaction rate being 1.43 times higher than pure Ag 3 PO 4 . The strategy of using TiO 2 as activity and stability promoter to construct the composite may be useful in developing highly active and stable visible-light photocatalyst for pollutants removal. [ABSTRACT FROM AUTHOR]

• Amorphous NiO x brings unique urbach tail absorption in near infrared region. • The disorder feature gives rich active site to boost rate-limiting water oxidation. • Ultrathin structure and external electron capture greatly prolong carrier lifetime. • It enlightens pure water splitting up to 680 nm with an AQE of 6.2 % at 420 nm. Harvesting near infrared light for water splitting opens up a new avenue in solar conversion but suffers from the low photon energy. Towards this, amorphous a-NiO x is reported to exhibit strong long-wavelength urbach tail absorption and provide abundant oxidation active sites due to its disordered structure. And its intrinsic two-dimensional ultrathin structure shortens the migration distance of photoinduced carriers. This enlightens water splitting under 680 nm red light when combined with electron captures like reduced graphene oxide. Furthermore, a-NiO x ||C 3 N 4 heterojunction is constructed to extend the light response from UV to near infrared region, together with a built-in-electric field to facilitate interfacial charge separation. The unique structure achieves stoichiometric water splitting under simulated sunlight with an apparent quantum efficiency of 6.2 % at 420 nm, outperforming most state-of-art photocatalysts. This work may bring new opportunities in modulating amorphous materials for artificial photocatalysis. [ABSTRACT FROM AUTHOR]

It is still challenging to adjust the desired structure and heterojunction interface of photocatalytic materials by a facile and efficient strategy. In this manuscript, variable dimensional structured BiOI with surface oxygen vacancies (OVs) were prepared via an in-situ growth on mesoporous g-C 3 N 4 nanosheets through one-pot synthesis at room temperature, which possesses the p-n heterojunction required for the high-performance photocatalysis. By reducing the amount of the precursor of BiOI during the reaction, the morphology of BiOI gradually changed from 3D microspheres to 2D nanosheets and even 0D nanoparticles, which were conjugated with ultrathin g-C 3 N 4 nanosheets forming the composites with 2D/3D, 2D/2D, and 2D/0D structure, respectively. The catalyst with the best performance was determined to be the g-C 3 N 4 /BiOI with 2D/2D structure, which provides a larger contact surface, appropriate bandgap, and the higher utilization of visible light. The synergies between heterostructure and OVs can promote both the production and the separation of electron-hole effectively, and hence producing more oxidizing •O 2 − and h+ with the energy input. Thereby, under visible light, the optimized combination of g-C 3 N 4 /BiOI heterojunction can exhibit the outstanding photocatalytic performance of degrading 99% rhodamine B within 2 h, which was 2.6 and 12.8 times faster than pure g-C 3 N 4 and pure BiOI, respectively. In addition, our work provides a feasible and adjustable approach to regulate the structure and heterojunction interface of photocatalysts as well as the discussion about the variable dimensional structure-activity relationship in photocatalysis. Image 1 • An one-step in-situ growth method was used for photocatalytic composites. • Variable dimensional structured BiOI with OVs loaded on 2D g-C 3 N 4 nanosheets. • Optimal 2D/2D structured g-C 3 N 4 /BiOI exhibited the best photocatalytic activity. • Synergies of heterostructure and OVs promoted the separation of electron-holes. • Dimensional structure-activity relationship in photocatalysis was determined. [ABSTRACT FROM AUTHOR]

• NiCoP/TiO 2 sensitized system is constructed by tuning the band structure of NiCoP. • NiCoP sensitizes TiO 2 under visible light to form unbalanced charged surface. • The unbalanced charged surface enhances the activation of B–H and H–O bonds. • H 2 evolution rate is enhanced to 3 folds compared with dark reaction. • Full range visible light can be used. Hydrolysis of ammonia borane is promising for instantaneously supplying hydrogen with moderate temperatures. Herein, we utilize NiCoP/TiO 2 sensitized system to construct a highly unbalanced charge distribution for rapid H 2 generation under visible light. The key point is optimizing the band structure to ensure electron injection from NiCoP to TiO 2 because Ni 2 P and CoP cannot form this structure. Under visible light NiCoP is excited and inject electron to TiO 2 , generating a highly unbalanced but stable charge distribution. The positively and negatively charged NiCoP and TiO 2 serve as activation sites for NH 3 BH 3 and H 2 O, respectively. The H 2 generation rate is increased from 0.18 mL/s in darkness to 0.36 mL/s under visible light, with E a reduced from 52.76 kJ/mol to 25.89 kJ/mol. After modifying TiO 2 with 2.5%Pt, the reaction is further increased to 0.55 mL/s. Full visible light can promote the reaction, with each photon trigger two NH 3 BH 3 molecules for reaction. [ABSTRACT FROM AUTHOR]

• All-in-one Pt·Ni(OH) 2 /C 3 N 4 photocatalyst realizes one-step overall water splitting. • Pt·Ni(OH) 2 /C 3 N 4 achieves a prominent AQE of 4.2% at 420 nm and excellent stability. • Both H 2 O activation and charge transfer are dramatically enhanced. • The backward recombination of H 2 and O 2 is suppressed. Overall water splitting is vital in solar-hydrogen conversion. In addition to charge separation, the regulation of surface kinetics and suppression of backward reaction become particularly crucial. Herein, an all-in-one Pt·Ni(OH) 2 /C 3 N 4 photocatalyst is proposed by integrating Pt@Ni(OH) 2 composited nanowires and isolated Pt clusters on C 3 N 4. In this heterostructure, Pt@Ni(OH) 2 with rich coordinatively unsaturated sites effectively boost O 2 evolution, and Pt-O-Ni interaction retards O O bond cleavage thus inhibiting backward H 2 O regeneration. Meanwhile isolated Pt forms an Schottky junction with C 3 N 4 for electron transfer and proton reduction. Consequently, Pt·Ni(OH) 2 /C 3 N 4 achieves stoichiometric water splitting with H 2 /O 2 evolution of 1330/632 μmol g−1 h−1, and an outperforming AQE of 4.2% at 420 nm. Our work manifests that accelerating charge migration, inhibiting backward reaction and tuning surface kinetics are dominant in water splitting, for which a rational design of robust redox pathways is necessary. [ABSTRACT FROM AUTHOR]

• MnO x -decorated 3D porous C 3 N 4 is fabricated by NaCl-templated method. • C 3 N 4 possesses donor–acceptor system by Na ions and cyano groups. • MnO x modulate holes transfer and provide oxidation sites. • C 3 N 4 shows quick charge separation and stronger reduction capability. • C 3 N 4 achieves 18-fold higher H 2 production rates of bulk C 3 N 4 under visible light. Carbon nitride is an intriguing visible-light photocatalyst for H 2 production but suffers from low surface area and fast charge recombination. Here, we report a simple yet efficient approach to fine tune the porous structure, modify the electronic structure and carrier behaviors of C 3 N 4 through in-situ growth of MnO x by NaCl template-assisted strategy. This NaCl template method simultaneously constructs 3D porous structure for high surface area, induces Na coordination with N atoms and accompanying cyano group to form an internal donor-acceptor system for efficient charge transfer and separation. Along with the MnO x growth, the band gap of C 3 N 4 is narrowed for stronger visible light absorption and the conduction band level is negatively shifted for stronger reduction capability. Thus, the resulted C 3 N 4 (MSCN) shows much improved activity of about 18 times higher than bulk C 3 N 4 in photocatalytic hydrogen evolution reaction under visible light irradiation. [ABSTRACT FROM AUTHOR]

Review: [syntheses, properties, and energy-related applications; 91 refs. [ABSTRACT FROM AUTHOR]