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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]

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]

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]

[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]

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]

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]

Solar energy can generate hydrogen via water splitting, which could decrease the environmental pollutions. During the photocatalytic hydrogen generation, some semiconductors can improve efficiencies. Recently, graphitic carbon nitride (g-C3N4) attracts interests due to visible light response. However, pristine g-C3N4 exhibits low photocatalytic activity. In this work, Au nanorods (Au NRs) were prepared via the colloidal seed-mediated approach, which assembled different structures by L-Cysteine (L-Cys). Meanwhile, the g-C3N4 was synthesized by means of thermal condensation of melamine. Based on this, we reports some photocatalysts by combining different Au NRs structures (random, aligned and aggregated) with g-C3N4. The hydrogen generation rates of different Au NR/g-C3N4 composites are 30.1 μmol h−1 g−1 (aligned), 44.5 μmol h−1 g−1 (random) and 46.9 μmol h−1 g−1 (aggregated), respectively. Interestingly, the hydrogen evolution rates are proportional to the surface plasmon resonance (SPR) enhancements of different Au NRs structures. The random and aggregated structures with some vertical Au NRs in contact with g-C3N4, can provide a better circuit for continuous flow of hot charge carriers. Nevertheless, horizontally aligned Au NRs reduce the Schottky barrier between Au NRs and g-C3N4, which enhances the back electrons and thus slow down the hydrogen generation. Our work reveals the effective Au/semiconductor photocatalysts to fabricate the vertically oriented Au NR layer contact with the semiconductor surface. This represents one of the future directions in this field. The preparation of different photocatalysts based on pristine g-C3N4 and aligned Au NR structures with g-C3N4. Our present work reveals the effective Au/semiconductor photocatalysts are to fabricate a highly vertically oriented Au NR layer with the ends of the Au NRs in direct contact with the semiconductor surface. This represents one of the future directions in this field. [ABSTRACT FROM AUTHOR]

P-doped graphitic carbon nitride tubes (P-CNTS) with different P concentrations were successfully fabricated via a pre-hydrothermal in combination with a calcination process under a nitrogen atmosphere. The as-prepared samples exhibited excellent photocatalytic performance with a hydrogen production rate (HPR) of 2749.3 μmol g−1 h−1, which was 17.5 and 6.6 times higher than that of the bulk graphitic carbon nitride (CNB) and graphitic carbon nitride tube (CNT). The structural and textural properties of the P-CNT samples were well-investigated via a series of characterization methods. Compared with the bulk g-C3N4, the tubular structure of the doped samples was provided with a larger specific surface area (SSA) and a relatively rough interior. Besides the above, surface defects were formed due to the doping, which could act as more active sites for the hydrogen production reaction. In addition, the introduction of the P element could effectively adjust the band-gap, strengthen the harvest of visible-light, and boost the effective separation of photogenerated charges. More interestingly, these findings can open up a novel prospect for the enhancement of the photocatalytic performance of the modified g-C3N4. [ABSTRACT FROM AUTHOR]