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[Display omitted] • Hydrothermal treatment induced biuret recrystallization to form biuret hydrate with regular morphology and large crystal size. • Biuret hydrate as precursor promoted the thermal polymerization of melem for the formation of graphitic carbon nitride (BCN-HT100) network. • The obtained BCN-HT100 possessed ultrathin nanosheet structure with high polymerization degree, large surface area and plenty of pores. • Photocatalytic overall water splitting was achieved with the AQY reaching 5.8% at 380 nm and 4.9% at 405 nm. Structure regulation (including electronic structure and morphology) for graphitic carbon nitride (g-C 3 N 4) is an effective way to promote the photocatalytic activity. Herein, an ultrathin porous g-C 3 N 4 (BCN-HT100) was synthesized by calcination of biuret hydrate. Hydrothermal treatment induced biuret recrystallization to form biuret hydrate precursor with regular morphology and large crystal size, thus promoting the polymerization of melem to form g-C 3 N 4 network. Accordingly, BCN-HT100 possessed ultrathin nanosheet structure, higher polymerization degree, larger surface area and more pores than biuret-derived g-C 3 N 4. BCN-HT100 behaved high-efficiency photocatalytic H 2 -productin activity with an apparent quantum yield (AQY) of 58.7% at 405 nm due to the enhanced utilization efficiency for photo-generated charge carriers and abundant reactive sites. Furthermore, Pt-NiCo 2 O 4 dual cocatalysts were employed on BCN-HT100 for achieving photocatalytic overall water splitting, and the AQY reached 4.9% at 405 nm. This work provides a meaningful reference to designing g-C 3 N 4 to achieve efficient solar energy conversion into hydrogen. [ABSTRACT FROM AUTHOR]

For the dye-sensitized heterogeneous photocatalytic system, the main challenge is the design of support materials with low cost, good adsorption capacity and facilitated electron transfer ability. Herein, an amorphous/crystalline SnO 2 /BaSO 4 composite with unique leaf-like morphology composed of four protruded corners was developed by an one-pot coprecipitation method at room temperature. The low-cost crystalline BaSO 4 acted as the support material for Eosin Y (EY) sensitization and did not inhibit the light absorption of EY, and the amorphous SnO 2 uniformly coated on BaSO 4 provided good conductivity to benefit for the transport of photogenerated carriers. Therefore, under visible-light irradiation (λ ≥ 420 nm), the EY-sensitized SnO 2 /BaSO 4 showed excellent photocatalytic activity with H 2 -production rate of 263 μmol h−1, which was 7.5 times that of EY or EY-sensitized bare BaSO 4 , and the apparent quantum yield achieved to be 11.2 % at 500 nm. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of type‐II BaSnO3/g‐C3N4 heterojunction composites are prepared by anchoring BaSnO3 on g‐C3N4 via a facile solvothermal method. BaSnO3 is applied as an electron transport promoter in the field of photocatalytic H2 production under visible light for the first time. BaSnO3 shows excellent performance in collecting and transferring photogenerated electrons from g‐C3N4 to reactive sites, thus effectively inhibiting the recombination of photogenerated electron–holes. Consequently, the photocatalytic H2‐production activity of BaSnO3/g‐C3N4 composite is enhanced up to 3.2 times compared to that of pristine g‐C3N4. This work provides a meaningful reference for the application of electron transport materials in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

A dual-precursors co-pyrolysis strategy was adopted to prepare photocatalysts of MoO 3 /g-C 3 N 4 composite from MoS 2 /melamine through a facile one-pot method. By following this strategy, MoS 2 was in-situ transformed to MoO 3 accompanying with the pyrolysis and polymerization of melamine to g-C 3 N 4 nanosheets. A set of samples about MoO 3 /g-C 3 N 4 composite containing different MoO 3 contents were prepared and the visible-light driven photocatalytic performance of samples were investigated. The photocatalytic activity was notably enhanced and the highest evolution rate for H 2 reached 13.9 times and 2.5 times that of the pristine g-C 3 N 4 and the MoO 3 /g-C 3 N 4 derived from MoO 3 /melamine, respectively. On the one hand, layered MoS 2 used as the precursor of MoO 3 contributed to the intimate contact with g-C 3 N 4 nanosheets and the high dispersity of derived MoO 3 , and on the other hand, the morphology and electronic structure of g-C 3 N 4 were actually changed by the strong interaction between the MoO 3 and g-C 3 N 4 , thus inducing an efficient Z-scheme (S-scheme) system in the composite. The above-mentioned co-operation effect in the composite resulted in the significant improvement on the activity of photocatalytic H 2 evolution. This work presented a valuable reference, by taking MoO 3 /g-C 3 N 4 as an example, for the construction of composite-photocatalyst system in visible-light-driven H 2 evolution. Image 1 • MoO 3 /g-C 3 N 4 photocatalyst was prepared by one-pot pyrolysis of MoS 2 /melamine. • H 2 -evolution rate was higher than those of g-C 3 N 4 and sample from MoO 3 /melamine. • Layered MoS 2 contributed to well dispersity and contact of derived MoO 3 on g-C 3 N 4. • Dual-precursors in-situ transformation process influenced the structure of g-C 3 N 4. • Interaction between MoO 3 and g-C 3 N 4 was enhanced to form efficient Z-scheme system. [ABSTRACT FROM AUTHOR]

Co 3 (OH) 2 (HPO 4 ) 2 /LaTiO 2 N composites with a special microstructure were constructed by in-situ hydrothermally growing Co 3 (OH) 2 (HPO 4 ) 2 nano-needles on the surfaces of LaTiO 2 N irregular brick-like chunks. An effective heterojunction in the composites was formed based on the matched band structures and the close interfacial combination between Co 3 (OH) 2 (HPO 4 ) 2 and LaTiO 2 N, and thus improved the separation and transfer of photo-generated carriers. Consequently, photocatalytic O 2 -evolution activity of the composites was enhanced up to 3.5 times that of LaTiO 2 N. [ABSTRACT FROM AUTHOR]

(LaTiO2N)1−x(LaCrO3)x continuous solid solutions with an orthorhombic-phase ABX3 perovskite structure and with varied LaCrO3 contents (0 ≤x≤ 1) were synthesized by a polymerized complex method followed by a post-treatment process of nitridation for the first time. Visible-light-driven photocatalytic H2-evolution activities of the solid solutions gradually increased with the increase of x from 0.0 to 0.3, and then sharply decreased with the further increase of x from 0.3 to 1.0. With the increase of x, on the one hand, the narrowed bandgaps of solid solutions would enhance the generation of charge carriers and the increased lattice distortion of solid solutions could promote the separation and migration of charge carriers, thus mainly contributing to the improvement of photocatalytic activities; on the other hand, the lowered CBMs of solid solutions would reduce the driving force for reducing H2O to H2 and the decreased surface areas of solid solutions would weaken the adsorption of reactants and reduce the reactive sites, thereby resulting in the deterioration of photocatalytic activities. [ABSTRACT FROM AUTHOR]

MoS 2 is widely applied in photocatalytic H 2 evolution to function as an efficient cocatalyst, whereas it is not yet reported that this material acted as an effective host photocatalyst in this field. Herein, MoS 2 nanosheets were prepared by a general hydrothermal process at first, and then treated with flowing NH 3 at temperatures from 400 to 900 °C to develop a series of novel MoS 2 -based photocatalysts, which showed considerable photocatalytic activities for H 2 evolution under visible-light irradiation. It was deduced from different instrumental characterizations on the physicochemical properties of photocatalysts that the enhancement of photocatalytic activity by high-temperature NH 3 treatment could be mainly attributed to the modification of surface properties (such as electric property and acid-base properties) by N, which promoted the adsorption of reactants and further accelerated photocatalytic reaction. This work presented an effective route to explore new H 2 -evolution photocatalysts by modifying the appropriate materials that were commonly employed as cocatalysts. [ABSTRACT FROM AUTHOR]

It has been found in this study that the combination of ZIF-8 and g-C 3 N 4 turns the photo-inactive ZIF-8 into "active" and significantly enhances the photocatalytic performance for H 2 production. The experimental results such as contact potential difference (CPD) and photodeposition analysis suggest that a built-in electric field exists at the interface of g-C 3 N 4 and ZIF-8, and the direction is from ZIF-8 to g-C 3 N 4. Furthermore, the theoretical calculation of charge density difference and work functions uncover the potential forming mechanism of the built-in electric field. The mechanism analysis exhibits that the built-in electric field is conducive to promote the directional transfer of photo-induced electrons from g-C 3 N 4 to ZIF-8, which significantly boosts the catalytic ability. Hence, the construction of a built-in electric field is considered to be an effective strategy to synthesize robust photocatalysts, and the strategy can be extended to prepare a range of advanced catalysts needing directional charge transfer. [Display omitted] • Photo-inactive ZIF-8 is turned into "active" by built-in electric field. • Photo-inactive ZIF-8 become "active" and acts as the photo-reduction site. • The incorporation of ZIF-8 and g-C 3 N 4 improve the photocatalytic ability for 10 times. • The mechanism was detailly uncovered by the consistent experiments and calculations. [ABSTRACT FROM AUTHOR]

Abstract: Visible-light-driven semiconducting photocatalysts of Ag3PO4 were prepared by a hydrothermal method, and were optimized by adjusting reaction conditions, i.e., temperature, pH of reaction solution, concentration of feedstock, and time of hydrothermal process. The obtained photocatalysts were then systematically characterized by different instruments, such as XRD, UV–vis, FESEM, and BET, to reveal the physicochemical properties. Furthermore, activities of photocatalysts for visible-light-driven O2 evolution were evaluated, demonstrating that the photocatalytic activity of Ag3PO4 prepared by hydrothermal reaction (initial rate of O2 evolution, 1156 μmol g−1 h−1) was more than two times as that of sample prepared by room-temperature reaction (initial rate of O2 evolution, 533 μmol g−1 h−1), which could be attributed to its better ability to utilize visible light and more regulated morphology. [Copyright &y& Elsevier]

[Display omitted] Due to structural tunability, high surface area, abundant pore structures, and abundant active sites, covalent heptazine frameworks (CHFs) constructed from heptazine and other molecular blocks are especially prominent. Here, we proposed a reaction-dependent strategy for designing two dimensional CHFs including high-throughput precursors screening, structure generation, and performance evaluation. Assuming that oxamide-like precursors can undergo the same thermal polymerization reaction as producing C 6 N 7 , seven precursors were screened from more than 109 molecules in the ZINC20 database in terms of molecular weight, number of substructures, shape index, and symmetry. Furthermore, CHF-L1 to CHF-L7 were constructed from urea and the seven precursors according to the topologically assembling scheme in thermal polymerization. The designed CHFs had band gaps ranging from 1.89 to 3.10 eV. Among them, CHF-L3 assembled structurally by urea and 1,2,4,5-tetrazine-3,6-dicarboxamide with the smallest bandgap and an oxidative potential bias of 1.38 V for oxygen evolution reaction was screened as the candidate with high oxidative ability. The negative formation energy based on the synthesis route indicated the synthetic feasibility of CHF-L3, and negative cohesive energy as well as the stable structure under ab initio molecular dynamics simulations confirmed the stability of CHF-L3. The present work is expected to provide a powerful design strategy for two-dimensional CHFs design and is broadly applicable to various computational covalent organic framework design systems and experimental studies. [ABSTRACT FROM AUTHOR]

The metal-free graphitic carbon nitride (g-C 3 N 4) with a series of merits like low cost, favorable stability, and controllable two-dimensional graphite-like structure, has been extensively studied for photocatalytic H 2 evolution. Composite engineering is regarded as one of effective strategies to adjust the kinetics of photogenerated carriers in g-C 3 N 4 for elevating its photocatalytic performance. Herein, the composite system of g-C 3 N 4 with oxynitride LaTiO 2 N was elaborately constructed for improving photocatalytic H 2 -evolution performance. With systematical characterizations, the partial cover of g-C 3 N 4 nanosheets on LaTiO 2 N (LaTiO 2 N@g-C 3 N 4) was verified and promoted the sufficient contact between g-C 3 N 4 and LaTiO 2 N, accompanied by the formation of the (oxy)nitride heterojunction. Benefited by the well-matched band structures for g-C 3 N 4 and LaTiO 2 N, the (oxy)nitride heterojunction strengthened the separation of photogenerated carriers and therefore enhanced the photocatalytic performance of g-C 3 N 4. This work gives more insight in composite engineering on g-C 3 N 4 , and also provides feasible guidelines for designing g-C 3 N 4 -based photocatalysts towards improving photocatalytic performance. [Display omitted] • Composites of g-C 3 N 4 and LaTiO 2 N were created to promote photocatalytic H 2 evolution. • g-C 3 N 4 nanosheets partially covered the surface of LaTiO 2 N (LaTiO 2 N@g-C 3 N 4). • (Oxy)nitride heterojunction between g-C 3 N 4 and LaTiO 2 N was formed. • Separation of photogenerated carriers was enhanced by (Oxy)nitride heterojunction. [ABSTRACT FROM AUTHOR]

[Display omitted] Graphite carbon nitride (g-C 3 N 4) as metal-free photocatalyst has been widely studied recently in photocatalytic water reduction, which is considered as one of the promising routes to realizing the hydrogen energy-based society in the future. The generally used preparation process based on thermal polymerization of precursors easily brought the formation of aggregated nanosheets morphology, severely limiting its photocatalytic activity. Herein, the hollow tube-like morphology with porous surface was elaborately obtained by ethylene diamine tetraacetic acid (EDTA)-involved hydrothermal treatment of melamine precursor. The hollow and porous features shortened the migration distance of photo-generated carriers, trapped the incident lights, and provided more photocatalytic reactive sites, then realizing the enhanced photocatalytic H 2 -evolution activity up to 7.1 times that of pristine g-C 3 N 4. The presence of EDTA acted as the pivotal role to control the recrystallization process of melamine and its derivative, cyanuric acid, and thus to determine the framework formation of the hollow tube-like microstructure. Moreover, complete thermal decomposition of cyanuric acid during the thermal polymerization of precursors was responsible for the hollow and porous features. This work extends the morphology regulation cognition of g-C 3 N 4 based on hydrothermal treatment of precursors, and is expected to bring deep understanding and feasible strategies to design morphology-dominated highly-efficient g-C 3 N 4 photocatalysts. [ABSTRACT FROM AUTHOR]

• Nanosized MoP was synthetized in a novel phosphorization process under an ambient-air atmosphere and assembled with g-C 3 N 4. • The incorporation of MoP into g-C 3 N 4 built a conducive highway (Mo(δ+)−N(δ−)) for electrons transfer from g-C 3 N 4 to MoP. • The optimal MoP/g-C 3 N 4 possessed H 2 -production rate of 3868 μmol h−1 g cat −1 and the corresponding AQY reached 21.6 % at 405 nm. In this work, nanosized MoP was synthetized in a novel phosphorization process at a relatively low temperature under an ambient-air atmosphere and then assembled with g-C 3 N 4 to form MoP/g-C 3 N 4 coupled photocatalyst by a mixing and heat-treating method. Significantly, the obtained noble-metal-free MoP/g-C 3 N 4 photocatalyst showed superior photocatalytic H 2 -production activity and excellent stability than most reported noble-metal-free cocatalysts modified g-C 3 N 4. The optimal MoP/g-C 3 N 4 photocatalyst possessed a H 2 -production activity of 3868 μmol h−1 g cat −1 and the corresponding AQY reached 21.6 % at 405 nm. The incorporation of nanosized MoP into g-C 3 N 4 could broaden the absorption range of visible light, built a conducive highway (Mo(δ+)−N(δ−) bond) for electrons to transfer from g-C 3 N 4 to MoP, which improved the separation and transportation efficiency of charge carriers, and reduce the energy barrier for hydrogen evolution reaction. This work provided a reliable guideline for designing novel and simple synthetic method for cocatalyst and then constructing cocatalyst/photocatalyst coupled structure. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride is considered as one of the most potential photocatalysts for utilizing solar energy. Herein, an efficient route of rapid high-temperature treatment (at 800 °C in air for 0–20 min) was developed to modify pristine graphitic carbon nitride. It was found that, after rapid high-temperature treatment, the obtained photocatalysts showed greatly enhanced photocatalytic H 2 -evolution activities (around 25.5 times) under visible-light irradiation attributed to the following reasons. More active sites for photocatalytic reaction were provided by the significant increase of surface areas. The generation, separation and transfer of photo-generated carriers were effectively promoted by the quantum confinement effect of thinner graphitic carbon nitride sheets and by the generated nitrogen vacancies in C N heterocyclic units. Moreover, stronger driving force for photocatalytic H 2 -evolution reaction was obtained to enhance the ability of water reduction reaction. [ABSTRACT FROM AUTHOR]

A nanohybrid of CdS and HCa 2 Nb 3 O 10 with enhanced separation of charge carriers was conveniently prepared by self-assembly of negatively charged HCa 2 Nb 3 O 10 nanosheets with the existence of Cd 2+ followed by sulfuration. With CdS working as a visible light absorbent, HCa 2 Nb 3 O 10 , with a wide bandgap, showed H 2 evolution activity without cocatalysts upon visible light excitation and neutral pH (450 μmol h −1  g cat −1 ), and showed a high quantum efficiency of 7.2% at 425 nm because of enhanced charge separation. The self-assembly method rapidly realized introduction of guest materials into the interlayer space of layered perovskites from a layer-by-layer strategy, showing great potential in synthesizing novel 2D material based hybrid photocatalyst. A type II composite band structure was obtained from combination of CdS and niobates, making it possible for spontaneous charge separation. While ultra-fine nature of the guest CdS, ultra-thin nature of the host niobate nanosheets and close junction between the host and guest components facilitated charge transfer between components. Enhanced charge separation in hybrid photocatalyst is the key factor that leads to its superior photocatalytic performance in comparison with its components. This work extends photocatalytic application of wide gap niobates into visible light region. Since the unique nanostrucute and charged nature of 2D materials can be fully utilized, it is believable that more efficient photocatalytic water splitting can be realized by constructing nanosheets based hybrids in the future. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride suffers terrible recombination of photo-generated carriers and thus usually results in limited photocatalytic activity. Improving crystallinity and creating novel structure can effectively alleviate the aforementioned problem. Herein, a high-cyano groups-content and amorphous-crystalline carbon nitride isotype heterojunction (BCN-NaK) was obtain via a post treatment strategy in eutectic salt. The cyano groups acted as electron acceptors, and the intimate isotype heterojunction constructed by amorphous carbon nitride and crystalline poly-heptazine-imide built interfacial electric field. Both synergistically enabled BCN-NaK more efficient charge transfer than other amorphous and crystalline carbon nitrides. Comprehensive and systematic analysis demonstrated that the promoted charge transfer made the predominant contribution to the ultrahigh photocatalytic H 2 -production activity of BCN-NaK with an excellent apparent quantum yield of 68.9 % at 405 nm. In addition, BCN-NaK exhibited a good photocatalytic CO 2 -to-CO conversion rate of 22.8 μmol h−1 g cat −1 without adding sacrificial agent or loading metal under visible light. [Display omitted] • A high-cyano groups-content and amorphous-crystalline carbon nitride isotype heterojunction (BCN-NaK) was developed. • The cyano groups and interfacial electric field built by isotype heterojunction synergistically promoted charge transfer. • BCN-NaK showed much better photocatalytic activity than other amorphous and crystalline carbon nitrides. • BCN-NaK showed high-quantum-yield H 2 production (AQY : 68.9 % at 405 nm) and enhanced CO 2 reduction. [ABSTRACT FROM AUTHOR]

Na-doped graphitic carbon nitride was successfully developed by a one-pot preparation, that was, by simply annealing the mixture of melamine and organometallic sodium salt (ethylenediamine tetraacetic acid disodium salt). Visible-light-driven photocatalytic H 2 -evolution activity of graphitic carbon nitride was effectively enhanced by Na doping (9.2 times). It was found based on comprehensive analysis that, the absorption of visible light was improved due to the structural change of graphitic carbon nitride by Na doping, thereby promoting the generation of more photo-generated carriers. Meanwhile, the separation and transfer of photo-generated carriers were greatly enhanced by coordination of Na into big C-N rings of the triazine units. Moreover, more active sites for photocatalytic H 2 -evolution reaction were provided by the increased surface areas. [ABSTRACT FROM AUTHOR]