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N-rich precursors govern the thermal polymerization formation of graphitic carbon nitride (g-C 3 N 4) based catalysts towards enhanced photocatalytic performance. In this paper, Cu components were introduced in superior thin g-C 3 N 4 nanosheets using the thermal polymerization copper acetate and bulk g-C 3 N 4 created by different precursors including melamine, dicyandiamide, and thiourea, such as melamine-g-C 3 N 4 (MCN), dicyandiamide-g-C 3 N 4 (DCN), and thiourea-g-C 3 N 4 (TCN). The performance of Cu-g-C 3 N 4 nanosheets depended strongly on the precursors of bulk g-C 3 N 4 samples. The well-developed Cu nanoparticles with clear lattice fringes were observed in the sample prepared using MCN (sample Cu-MCN) while the crystallinity of Cu nanoparticles became worse in the sample prepared using DCN (sample Cu-DCN). Interestingly, Cu clusters were homogeneously distributed in superior thin g-C 3 N 4 nanosheets in the case of using TCN (sample Cu-TCN) because of S components in thiourea affected the thermal polymerization. The photocatalytic activity of Cu-TCN was drastically improved compared with other Cu-g-C 3 N 4 samples. The photocatalytic hydrogen production rate of Cu-TCN with 1% of Cu components was 4035.6 μmol g-1 h-1. Cycle stability test indicated that sample Cu-TCN revealed high stability, in which the H 2 generation rate was retained 95% of their initial value after 5 cycles. These results supply efficient approaches for the study and application of g-C 3 N 4 based photocatalysts. • Cu components introduced in g-C 3 N 4 nanosheets using bulk g-C 3 N 4 created by different precursors. • Precursors (melamine, dicyandiamide, and thiourea) affect the activity of Cu-g-C 3 N 4 nanosheets. • Cu distribution in g-C 3 N 4 nanosheets depended on the thermal polymerization of precursors. • Cu clusters distributed in g-C 3 N 4 nanosheets created using thiourea revealed the best performance. [ABSTRACT FROM AUTHOR]

The design and development of efficient nitride photocatalysts have attracted much attention. Herein, two-dimensional mesoporous Ta 3 N 5 is successfully synthesized through a simple sol-gel process with filter paper as a biological template and a combination of vacuum nitriding reactions. The prepared Ta 3 N 5 shows a wide light response range up to the near infrared (NIR) region due to the nitrogen vacancies generated from substitution of N3− for O2− ions during vacuum nitridation. Significantly, such a narrow bandgap (∼1.99 eV) still satisfies the redox potential of water splitting in thermodynamics. The experimental results show that the Ta 3 N 5 photocatalyst exhibits an enhanced hydrogen production rate of 34.6 μmol h−1 g−1, which is 3.9 and 2.1 times higher than that of Ta 2 O 5 and partial nitridation of Ta 2 O 5 (N–Ta 2 O 5), respectively. This enhanced photocatalytic performance could be attributed to the high specific surface area to provide reactive active sites, substitution of N3− for O2− ions to optimize the band structure, and special two-dimensional mesoporous structure to shorten the charge transfer distance. This work provides a new perspective for the preparation of two-dimensional nitride materials by a biological template method combining vacuum nitriding with enhanced photocatalytic performance. Two-dimensional mesoporous Ta 3 N 5 is synthesized by a simple sol-gel process with filter paper as a biological template and vacuum nitriding reaction, leading to an efficient photocatalytic performance. [Display omitted] • Two-dimensional mesoporous Ta 3 N 5 was prepared by a biological template. • The prepared Ta 3 N 5 shows a wide light response range up to the near infrared region. • The special two-dimensional structure shortens the charge transfer distance. • The Ta 3 N 5 photocatalyst shows a superior hydrogen production performance. [ABSTRACT FROM AUTHOR]

The simultaneous production of hydrogen and biomass-based chemicals from biomass-derived feedstock aqueous solutions via photocatalysis is appealing because no additional sacrificial agent is needed. However, limited success has been achieved. This paper reports efficient nori-shaped carbon nitride-based photocatalysts with potassium/oxygen co-doping and cyano group introduction for efficient conversion of biomass-derived monosaccharides to produce lactic acid and hydrogen simultaneously. The obtained photocatalyst has an adjustable bandgap, fast migration/separation rate of photo-generated carriers and displays excellent photocatalytic performance with respect to xylose conversion (∼95.0%), lactic acid selectivity (90.5%) and hydrogen generation (∼33 380 μmol g−1 h−1) in the presence of visible light. The h+, ˙OH, ˙O2− and 1O2 drive xylose conversion and lactic acid production. For biomass-derived pentoses and hexoses, the reaction system also exhibits excellent photocatalytic activity of lactic acid selectivity and hydrogen generation; the reported photocatalyst has excellent reusability. This paper provides a new perspective for hydrogen generation and biorefineries via a photocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] Construction of Z-scheme heterojunctions has been considered one superb method in promoting solar-assisted charge carrier separation of carbon-based materials to achieve efficient utilization of solar energy in hydrogen production and CO 2 reduction. One interesting concept in nanofabrication that has become trend recent years is nanoarchitectonics. A heterostructure photocatalyst constructed based on the idea of nanoarchitectonics using the combination of g-C 3 N 4 , metal and an additional semiconducting nanocomposite is investigated in this paper. Z-scheme tungsten oxide incorporated copper modified graphitic carbon nitride (WO x /Cu-g-C 3 N 4) heterostructures are fabricated via immobilization of WO x on Cu nanoparticles modified superior thin g-C 3 N 4 nanosheets. Mechano-chemical pre-reaction and a two-step high-temperature thermal polymerization process are the keys in attaining homogeneous distribution of Cu nanoparticles in g-C 3 N 4 nanosheets. The horizontal growth of homogeneously distributed WO x nanobelts on Cu modified g-C 3 N 4 (Cu-g-C 3 N 4) base via solvothermal synthesis is achieved. The photocatalytic performances of the heterostructures are evaluated through water splitting and CO 2 photoreduction measurements in full solar spectrum irradiation condition. The presence of Cu nanoparticles in the composite system improves charge transport between g-C 3 N 4 and WO x and thus enhances the photocatalytic performances (H 2 generation and CO 2 photoreduction) of the composite material, while the presence of WO x nanocomposites enhances light absorption of the composite material in the near infrared range. The synthesized heterostructure with optimized WO x to Cu-g-C 3 N 4 ratio and in case of no co-catalyst addition exhibits enhanced photocatalytic H 2 evolution (4560 μmolg-1h−1) as well as excellent CO 2 reduction rate (5.89 μmolg-1h−1 for CO generation). [ABSTRACT FROM AUTHOR]

Atomically precise Ni 6 (SC 2 H 4 Ph) 12 nanoclusters (Ni 6 NCs) supported on g-C 3 N 4 nanosheets were constructed to enhance the photocatalytic hydrogen evolution performances. [Display omitted] Much effort has been devoted to improving the photocatalytic capacity of graphitic carbon nitride (g-C 3 N 4). In this paper, we reported the successful synthesis of a hybrid photocatalyst with superb photocatalytic hydrogen production activity through decorating atomically precise Ni 6 (SC 2 H 4 Ph) 12 nanoclusters on g-C 3 N 4 nanosheets (labeled as Ni 6 /g-C 3 N 4) at room temperature. Zeta potential experiments demonstrated that the electrostatic interaction between Ni 6 and g-C 3 N 4 led to the formation of Ni 6 /g-C 3 N 4. The photocatalytic measurements revealed that the 5 %-Ni 6 /g-C 3 N 4 prepared with the original mass ratio of m(Ni 6)/m(g-C 3 N 4) = 1/20 exhibited the strongest hydrogen production activity. In the system with triethanolamine (TEOA) as the sacrifice agent, the visible-light hydrogen production rate reached up to 5.87 mmol h−1 g−1, approximately 290 times higher than that of pure g-C 3 N 4 (0.02 mmol h−1 g−1). Density functional theory (DFT) calculations testified that the above significant enhancement of photocatalytic hydrogen evolution of the hybrid photocatalyst arose from the photogenerated electrons transfer from Ni 6 to g-C 3 N 4. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) carried out from electrocatalysis of water splitting is playing a major role in the production of green and clean hydrogen. In this paper, we report on the synthesis of graphitic carbon nitride on nickel hydroxide (g-C 3 N 4 /Ni(OH) 2) nanocomposites by a simple ultrasonication method. The characterizations include the XRD, Raman, FESEM and electrochemical studies to analyze the performance of the as developed material over hydrogen evolution reaction. The morphological analysis shows that the aggregated interconnected g-C 3 N 4 /Ni(OH) 2 (GCN/NH) nanocomposites with an average particle size of ∼20 nm. These GCN/NH nanocomposites exhibit the lowest overpotential of 341 mV at 10 mA/cm2 which is smaller than that of the pristine Ni(OH) 2 nanosheets at 367 mV. Further, the Tafel slope for GCN/NH nanocomposites reveals a lower value of 131 mV/dec. As a result, g-C 3 N 4 decorated sheet-like β-Ni(OH) 2 exhibits the potential hydrogen evolution in alkaline KOH solution. Excitingly, the as developed hybrid β-Ni(OH) 2 nanocomposites show superior electrocatalytic behaviour during the hydrogen evolution reaction and also improve the catalytic stability than pure nanosheets. From these observations, one can say that this g-C 3 N 4 /Ni(OH) 2 nanocomposite electrocatalyst can play a splendid role in future energy technology. • One step synthesis of β-Ni(OH) 2 and g-C 3 N 4 /Ni(OH) 2 via sonochemical method. • Prepared electrodes were characterized for the electrocatalytic HER studies. • The electrochemically active surface area of nanocomposite is higher than that of the pristine. • The overpotential of the g-C 3 N 4 /Ni(OH) 2 nanocomposite is lower than that of the pristine Ni(OH) 2. [ABSTRACT FROM AUTHOR]

In this paper, a novel pristine carbon nitride (np-CN) with hollow capsule-like morphology was facilely prepared by the thermal polymerization of melamine and cyanuric chloride at 550 1C in air for 4 h. Then, modified carbon nitride (CN-P4mg) micro-flakes with zigzag edges were synthesized by the copolymerization of melamine, cyanuric chloride, and triaminotriphenylamine with a mass fraction of 0.13%. Analysis of the microstructure, surface state, porosity, and optoelectronic properties of the two samples indicates that CN-P4mg has a larger specific surface area and a lower bandgap than np-CN. Under visible light, CN-P4mg displays enhanced photocatalytic performance for the generation of hydrogen compared to that of np-CN and bulk graphite carbon nitride (g-C3N4). The photocatalytic hydrogen evolution rate of CN-P4mg reaches 16897.3 mmol g-1 h-1, which is 1.84 times that of np-CN and 72 times that of bulk g-C3N4. The experimental results confirm that the addition of triaminotriphenylamine provides a modified design for developing metal-free carbon nitride derivatives and a new route to study efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

Summary: There are various methods to produce hydrogen from water splitting as a substitute energy resource for fossil fuels in accordance with the global environmental crisis. Among these, water photocatalysis is considered one of the most renewable and sustainable processes simulated the solar energy utilized system in nature. During a half century, different kinds of photocatalysts were developed to convert photon energy into chemical energy to induce redox potential under visible light irradiation condition. In the beginning step, semiconductor materials, such as transition metal oxides, were explored extensively to use as a photocatalyst for hydrogen generation. However, semiconductor has limitations to act as an effective photocatalyst for water splitting due to the large band gap and recombination of charge carriers. Therefore, several kinds of modifications of structure or components have been studied to design visible light active photocatalysts for water splitting to generate hydrogen. Their performance was improved substantially by adding a noble metal or sensitizer to adjust the band gap and reduce the recombination of photoinduced charge carriers. Considering solar light‐induced photocatalytic hydrogen generation, various visible light active photocatalysts have been derived from carbon chain organic compounds and lattice crystals. This review classifies the visible light active photocatalysts as follows: (a) structural and chemical components of modified graphitic carbon nitride (g‐C3N4), (b) exfoliated perovskites, and (c) π‐bond conjugated polymers to produce hydrogen from water splitting. The hydrogen evolution efficiency of photocatalysts shows a great difference under visible light (λ > 400 nm) irradiation according to the three‐dimensional structure and electron transfer pathway. This is because the capability of restricting the recombination of photoinduced charge carriers and the band gap between the valence band and the conduction band of photocatalysts is dependent on the morphology and electrostatic interactions among components. This paper reviews visible light photocatalysts, that is, g‐C3N4 based materials, layered perovskites, and conjugated polymers, to provide integrated insight into photocatalytic water splitting to obtain hydrogen. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure evolution of polymeric carbon nitride was investigated and Au ions was used to improve its photocatalytic efficiency. Their structures were investigated by FT-IR, XPS, XRD, SEM and TEM. Their specific surface area and aperture distribution were measured by BET. Meanwhile, the energy band structure and electron-hole separation efficiency were analyzed by UV–Vis and PL spectroscopy. In addition, the photocatalytic performance of the photocatalysts was assessed by photocatalytic degradation of RhB and photocatalytic hydrogen evolution. The results showed that 600-PCN possessed the best photocatalytic performance, with a degradation rate of 46.92 % in 150 min. What's more, the degradation rate of RhB solution by 2 % Au/PCN reached 47.88 %, which was 2.17 times higher than that of 550-PCN (22.01 %). During the degradation process, h+ oxidatively degrade RhB. The hydrogen production rate of 2 % Au/PCN was about 11.658 μmol/g/h, which was 41.23 times higher than that of 550-PCN (0.282 μmol/g/h). • PCN is basically formed at 500 oC, but 600-PCN has better photocatalytic performance. • 2.0 % Au/PCN showed the best hydrogen production performance, with a hydrogen production rate of about 11.658 μmol/g/h. • 2.0 % Au/PCN showed the highest degradation rate of RhB solution with 47.88 %, and the main active substance is h+. [ABSTRACT FROM AUTHOR]

Adjusting the interlayer structure of carbon nitride is expected to adjust its physicochemical properties, thereby enhancing photocatalytic activity. In this paper, alkaline metal ion-intercalated carbon nitride was prepared by molten salt co-pyrolysis. Alkali metal ions acted as mediators to provide a new migration path for the photogenerated electrons of g-C3N4. The intercalation of K+ and Na+ reduced the bandgap value of carbon nitride, expanded the visible light absorption range, and promoted the separation and migration of charge carriers. As a result, the hydrogen production rate of DCN1 reached 500 μmol g−1 h−1, which was 10 times than that of pristine g-C3N4. Experimental and theoretical methods were used to explain the improvement of photocatalytic efficiency after K+ and Na+ were intercalated into the interlayer of g-C3N4. Our work provided a new idea for the design of high-efficiency hydrogen evolution photocatalysts via intercalation method. [ABSTRACT FROM AUTHOR]

Two dimensional (2D)/2D heterostructures with much interface is advantage to improve the transfer of photogenerated carriers. In this paper, SnS 2 nanosheets were horizontally grown on superior thin graphic carbon nitride (g-C 3 N 4) nanosheets to construct 2D/2D heterostructures with enhanced photocatalytic performance. The g-C 3 N 4 nanosheets (CN) were obtained by a two-step thermal polymerization at 600 and 700 °C. the growth of SnS 2 nanosheets was then carried out using a solvothermal synthesis. Preparation parameters including temperature, reaction time, and precursor components were tested to get optimized SnS 2 /g-C 3 N 4 composite sample 8SnS 2 -CN. A Z-scheme mechanism was proposed for the discussion of photocatalytic process. The degradation test of Rhodamine B (Rh B) indicated that the degradation rate of Rh B using sample 8SnS 2 -CN was twice quick compared with g-C 3 N 4 nanosheets, in which Rh B degradation was completed within 15 min. The photocatalytic hydrogen production rate of sample 8SnS 2 -CN was about 6 times that that of sample CN, which is 1818.75 μmol g−1 L−1. Enhanced photocatalytic performance is ascribed to SnS 2 deposited to form well-developed interface which improved the separation and transfer of photogenerated carriers. In addition, the growth of SnS 2 was also expended the photo adsorption. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, a visible light-driven polymeric carbon nitride (PCN)/(Pt)/nano-spherical MoS 2 photocatalysts was prepared using a self-assembly method. The structure of photocatalysts was explored by FT-IR, XPS, XRD, BET, SEM and TEM. Meanwhile, the energy band structure and electron hole separation efficiency were also analyzed by UV–Vis and PL spectra. In addition, the photocatalytic performance of photocatalysts were tested by photocatalytic degradation of Rhodamine B and photocatalytic hydrogen evolution. The results showed that PCN/2.0%MoS 2 showed the best photocatalytic performance, and the degradation rate of Rhodamine B could reach 98.39% within 150 min. Besides, the introduction of Pt nanoparticles significantly improved the photocatalytic activity. The degradation rate of Rhodamine B reached 100% within 150 min, and the rate of photocatalytic hydrogen production of PCN/Pt/MoS 2 system was increased by 21.3% over the PCN/2.0%MoS 2 system. The separation mechanism of electron and hole is Z-scheme mechanism and the main active substances for photocatalytic degradation were · O 2 − and h+. [Display omitted] • The catalyst is prepared by self-assembly. • Pt promotes the formation of carriers. • The transportation of carriers is Z-scheme. [ABSTRACT FROM AUTHOR]

Structural modulation of graphitic carbon nitride (g‐C3N4) remains a major challenge in rational catalyst design for artificial photosynthesis of valuable chemicals. Herein, a cellulose nanofiber (CNF) assisted polymerization is utilized to prepare 1D holey g‐C3N4 nanorods (HCN) with nitrogen vacancies and oxygen dopants for photochemical synthesis of lactic acid via monosaccharide photooxidation. The HCN exhibits a remarkable yield of 75.5% for lactic acid from a wide assortment of sugars such as hexose (C5) to pentose (C6), together with an excellent hydrogen production rate of 2.8 mmol h−1 g−1. Mechanistic studies confirm the rapid generation of superoxide radical is responsible for the superior activity, enjoying the synergetic effect between nitrogen vacancies and oxygen dopants. This work provides new directions for the design of green and efficient photocatalysts for biomass upgrading. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen-doped crystalline carbon nitride (CCNO) was successfully synthesized. • Pharmaceuticals and personal care products (PPCPs) were readily degraded by CCNO. • Hydrogen fuel was recovered from photocatalytic degradation of PPCPs by CCNO. • An energy-recovering wastewater treatment process using solar energy is proposed. Degrading organic pollutants while generating hydrogen from water splitting is an ideal application of photocatalysis. Herein, we presented an efficient photocatalyst, oxygen-doped crystalline carbon nitride, to power the degradation of various kinds of pharmaceuticals and personal care products and the simultaneous hydrogen production. The highest efficiency was achieved in treating the simulated wastewater containing naproxen (NPX), with the H 2 evolution rate of 819.1 µmol/g/h and the NPX degradation efficiency of 92 % upon visible light irradiation. Experimental and computational results suggested that the doped oxygen atoms thermodynamically favored the generation of hydroxyl peroxide for pollutant degradation and lowered the energy barrier of H 2 O reduction to produce hydrogen fuel. Most importantly, the catalysts functioned well in the natural aquatic environment including sea water, sewage water, river water, and well water. This study provides fundamental insights into photocatalytic water treatment with simultaneous hydrogen production, indicating an energy-recovering approach for wastewater treatment. [ABSTRACT FROM AUTHOR]