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Pt is usually used as cocatalyst for g‐C3N4 to produce H2 by photocatalytic splitting of water. However, the photocatalytic performance is still limited by the fast recombination of photo‐generated electrons and holes, as well as the poor absorption of visible light. In this work, MoO2/g‐C3N4 composites were prepared, in which MoO2 synergetic with Pt photo‐deposited during H2 evolution reaction worked as unilateral dual cocatalyst to improve the photocatalytic activity. Within 4 hours of irradiation, the hydrogen production rate of MoO2‐Pt dual cocatalyst modified g‐C3N4 reached 3804.89 μmol/g/h, which was 120.18 times of that of pure g‐C3N4 (GCN, 31.66 μmol/g/h), 10.98 times of that of MoO2 modified g‐C3N4 (346.39 μmol/g/h), and 9.18 times of that of Pt modified g‐C3N4 (413.64 μmol/g/h). Characterization results demonstrate that the deficient MoO2 not only promoted visible light absorption of g‐C3N4, but also worked as a "electron pool" to capture and transfer electrons to Pt. [ABSTRACT FROM AUTHOR]

Hydrogen evolution by photocatalytic technology has been one of the most promising and attractive solutions, and can harvest and convert the abundant solar energy into green, renewable hydrogen energy. As a new kind of photocatalytic material, graphitic carbon nitride (g-C3N4) has drawn much attention in photocataluytic H2 production due to its visible light response, ease of preparation and good stability. For a higher photocatalyic performance, N defects were introduced in to the traditional g-C3N4 in this work. The existence of N defects was proved by adequate material characterization. Significantly, a new absorption region at around 500 nm of N-deficient g-C3N4 appeared, revealing the exciting n-π* transition of lone pair electrons. The photocatalytic H2 production performance of N-deficient g-C3N4 was increased by 5.8 times. The enhanced photocatalytic performance of N-deficient g-C3N4 was attributed to the enhanced visible light absorption, as well as the promoted separation of photo-generated carries and increased specific surface area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen vacancy-mediated carbon nitride (DCNA) modified by deep eutectic solvents for the first time. • DCNA shows 4.93-fold improvement in atrazine removal. • Hole (h+) was found to be the most dominant active species for photocatalytic degradation of atrazine. • N–H of atrazine the side chain is the main adsorption site of DCNA. • The wheat growth toxicity test significantly reduced the degradation byproducts' toxicity. Metal-free photocatalysts like graphitic carbon nitride (g-C 3 N 4) can have their electronic structures altered by vacancy defect engineering, greatly increasing their catalytic activity. Here, we have synthesized nitrogen vacancy mediated carbon nitride (DCNA) modified by deep eutectic solvents for the first time, DCNA showed 4.93-fold improvement compared to pristine g-C 3 N 4 towards photocatalytic degradation of atrazine (ATZ). Besides, we have revealed the role of photogenic holes as the main active species for the photocatalytic degradation of ATZ. This improvement is attributed to the increased nitrogen vacancy, which increases the adsorption of N–H on the ATZ side chain, accelerates the process of photoelectron and hole separation, and allows more holes to participate in ATZ degradation. Moreover, the wheat growth toxicity test significantly reduced the degradation byproducts' toxicity. This study provides an effective method for preparing environmentally friendly metal-free photocatalysts with high catalytic performance. [ABSTRACT FROM AUTHOR]

• CN HP with hollow structure is successfully synthesized. • The tubular structure accelerates the charge separation. • The specific surface area of CN HP dramatically increased. • CN HP exhibits apparently raised photocatalytic H 2 O 2 generation. H 2 O 2 , as a green and environmentally friendly oxidant, has been widely used in our daily life and industrial production. It is of epoch-making significance to develop highly efficient photocatalysts for producing H 2 O 2. In recent years, g-C 3 N 4 has received much attention due to its high chemical stability, environmental friendliness and suitable energy band structure. However, some shortcomings including the fast recombination of photogenerated electron-hole pairs and small specific surface area in traditional 2D g-C 3 N 4 seriously impede its photocatalytic performance for the production of H 2 O 2. 1D hollow nanostructures possess intriguing physicochemical properties and are adopted to overcome the intrinsic shortcomings of g-C 3 N 4. Herein, g-C 3 N 4 with a hollow hexagonal prism structure (CN HP) is prepared to produce H 2 O 2. It is characterized by XRD, XPS, SEM, HRTEM, ESR and DRS. BET, PL spectra, photocurrent and EIS are used to explain the enhanced photocatalytic performance. Compared with traditional 2D g-C 3 N 4 , the specific surface area of CN HP increases to 41.513 m2/g, providing more active sites. Meanwhile, its hollow tubular structure can enhance the migration of photogenerated electrons to the catalyst surface, and electrons with a longer lifetime can participate in photocatalytic reactions to achieve high efficiency. The yield of H 2 O 2 production can up to 4.08 μmol over CN HP in 40 min, which is about 7 times higher than that of traditional 2D g-C 3 N 4 , and the apparent quantum efficiency (AQE) of H 2 O 2 production at 420 nm is 2.41%. This research provides a valuable reference for the development of green materials for efficient photocatalytic production of H 2 O 2. A carbon nitride hexagonal prisms (CN HP) with hollow structure is successfully constructed, which can significantly increase its specific surface area, so as to provide more active sites. Meanwhile, its hollow tubular structure can enhance the migration of photogenerated electrons to the catalyst surface, and electrons with longer lifetime are able to participate in photocatalytic reactions, thereby achieving excellent photocatalysis for H 2 O 2 generation. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] BiOBr-g-C3N4 was synthesized by a one-step chemical bath method at low temperature. [•] BiOBr-g-C3N4 showed much higher visible-light-driven (VLD) photocatalytic activity. [•] The interreaction between BiOBr and g-C3N4 is a kind of facet coupling between BiOBr-{001} and g-C3N4-{002}. [ABSTRACT FROM AUTHOR]

Pt is usually used as cocatalyst for g‐C3N4 to produce H2 by photocatalytic splitting of water. However, the photocatalytic performance is still limited by the fast recombination of photo‐generated electrons and holes, as well as the poor absorption of visible light. In this work, MoO2/g‐C3N4 composites were prepared, in which MoO2 synergetic with Pt photo‐deposited during H2 evolution reaction worked as unilateral dual cocatalyst to improve the photocatalytic activity. Within 4 hours of irradiation, the hydrogen production rate of MoO2‐Pt dual cocatalyst modified g‐C3N4 reached 3804.89 μmol/g/h, which was 120.18 times of that of pure g‐C3N4 (GCN, 31.66 μmol/g/h), 10.98 times of that of MoO2 modified g‐C3N4 (346.39 μmol/g/h), and 9.18 times of that of Pt modified g‐C3N4 (413.64 μmol/g/h). Characterization results demonstrate that the deficient MoO2 not only promoted visible light absorption of g‐C3N4, but also worked as a "electron pool" to capture and transfer electrons to Pt. [ABSTRACT FROM AUTHOR]

• Three novel-structured g-C 3 N 4 were obtained via microstructure engineering. • The photoabsorption, specific surface area and charge separation are all enhanced. • The porous outer-walls and inner-cores of PTYS CN-2 have abundant reactive sites. • The apparent quantum efficiency of H 2 evolution is as high as 11.8% at 420 nm. • CO production from CO 2 verified by the 13C isotopic labeling increases 5.6-fold. Photoabsorption, charge separation efficiency and surface reactive catalytic sites are three critical factors in semiconductor photocatalytic process, which determine the photocatalytic activity. For bulk g-C 3 N 4 derived from direct pyrolysis of C/N rich precursors, reactive sites distributed on the lateral edges are very scarce. In this work, we report the template-free preparation of three novel structured g-C 3 N 4 , namely, porous tubular (PT) g-C 3 N 4 , porous tubular yolk-shell (PTYS) g-C 3 N 4 , and porous split yolk-shell (PSYS) g-C 3 N 4 , by an unprecedented precursor microstructure regulation of melamine crystals in a gas-pressure mediated re-crystallization process. Enhanced photoabsorption, increased surface area, largely improved separation and migration efficiencies of photoinduced charge carriers are simultaneously realized in these g-C 3 N 4 structures. Noticeably, selective photo-deposition test uncovers that the porous outer-walls and inner-rods of PTYS g-C 3 N 4 are enriched by abundant reductive reactive sites, which consumedly boost the photo-reduction activity. Collectively promoted by these advantages, PTYS g-C 3 N 4 shows not only an efficient H 2 production activity with a high apparent quantum efficiency (AQE) of 11.8% at λ = 420 ± 15 nm, but also a superior CO 2 reduction for CO production than bulk g-C 3 N 4 by a factor 5.6, which is verified by the 13C isotopic labeling. This work develops precursor microstructure engineering as a promising strategy for rational design of unordinary g-C 3 N 4 structure for renewable energy production. [ABSTRACT FROM AUTHOR]

• Bi 3 O 4 Cl/g-C 3 N 4 vdW heterojunction is successfully fabricated. • The vdW force accelerates the charge separation at the Bi 3 O 4 Cl and g-C 3 N 4 2D/2D interface. • Bi 3 O 4 Cl/g-C 3 N 4 heterostructures exhibit apparently raised photocatalytic CO 2 conversion. • This strategy contributes to engineering Bi-based vdW heterojunctions for satisfactory solar energy conversion. The van der Waals (vdW) heterojunction formed between two-dimensional materials can break the anisotropy of the electron beam and is an effective method to improve the photocatalytic performance. Herein, vdW heterostructure is successfully constructed between layered Bi 3 O 4 Cl and 2D g-C 3 N 4 for photocatalytic CO 2 reduction. The weak vdW interaction enables Bi 3 O 4 Cl/g-C 3 N 4 with desirable moderate bandgap and built-in electronic field, which can efficiently separate the electron-hole pairs. As a result, Bi 3 O 4 Cl/g-C 3 N 4 heterostructures exhibit better photocatalytic CO 2 reduction activity compared with pure Bi 3 O 4 Cl and g-C 3 N 4. The optimized Bi 3 O 4 Cl/20%g-C 3 N 4 possesses the highest CO 2 conversion efficiency with CO and CH 4 generation rate of 6.6 and 1.9 μmol g−1 h−1, respectively. This work not only reports an effective reference for vdW heterojunction system based on Bi-based and g-C 3 N 4 semiconductors, but also contributes to engineering vdW heterojunctions for satisfactory solar energy conversion performance. [ABSTRACT FROM AUTHOR]