Rationally designed ternary CdSe/WS2/g-C3N4 hybrid photocatalysts with significantly enhanced hydrogen evolution activity and mechanism insight

Excellent light harvest, efficient charge separation and sufficiently exposed surface active sites are crucial for a given photocatalyst to obtain excellent photocatalytic performances. The construction of two-dimensional/two-dimensional (2D/2D) or zero-dimensional/2D (0D/2D) binary heterojunctions is one of the effective ways to address these crucial issues. Herein, a ternary CdSe/WS₂/g-C₃N₄ composite photocatalyst through decorating WS₂/g-C₃N₄ 2D/2D nanosheets (NSs) with CdSe quantum dots (QDs) was developed to further increase the light harvest and accelerate the separation and migration of photogenerated electron-hole pairs and thus enhance the solar to hydrogen conversion efficiency. As expected, a remarkably enhanced photocatalytic hydrogen evolution rate of 1.29 mmol g⁻¹ h⁻¹ was obtained for such a specially designed CdSe/WS₂/g-C₃N₄ composite photocatalyst, which was about 3.0, 1.7 and 1.3 times greater than those of the pristine g-C₃N₄ NSs (0.43 mmol g⁻¹ h⁻¹), WS₂/g-C₃N₄ 2D/2D NSs (0.74 mmol g⁻¹ h⁻¹) and CdSe/g-C₃N₄ 0D/2D composites (0.96 mmol g⁻¹ h⁻¹), respectively. The superior photocatalytic performance of the prepared ternary CdSe/WS₂/g-C₃N₄ composite could be mainly attributed to the effective charge separation and migration as well as the suppressed photogenerated charge recombination induced by the constructed type-II/type-II heterojunction at the interfaces between g-C₃N₄ NSs, CdSe QDs and WS₂ NSs. Thus, the developed 0D/2D/2D ternary type-II/type-II heterojunction in this work opens up a new insight in designing novel heterogeneous photocatalysts for highly efficient photocatalytic hydrogen evolution.     

Rich carbon vacancies facilitated solar light-driven photocatalytic hydrogen generation over g-C3N4 treated in H2 atmosphere

Graphite carbon nitride (g-C₃N₄) has caught far-ranging concern for its masses of advantages, for instance, the unique graphite-like two-dimensional lamellar structure, low cost, nontoxic, suitable bandgap of 2.7 eV and favorable stability. Whereas owing to the shortcomings of low solar absorptivity and fast recombination of photo-induced charge pairs, the overall quantum efficiency of photocatalysis for g-C₃N₄ is suboptimal, resulting in limited practicality of g-C₃N₄ (GCN). In our study, modified g-C₃N₄ materials (HCN) with ample carbon vacancies (CVs) were obtained through calcinating of g-C₃N₄ in H₂ atmosphere. Higher specific surface area and more active sites of HCN were induced by roasting of g-C₃N₄ in H₂. CVs that occurred in the N-(C₃) bond lead to the reduction of electron density around N, thus narrowing the bandgap of HCN-3h and enlarging corresponding light response capability. Under the synergistic function of abundant pore construction and CVs on HCN, the photo-excited e^?/h⁺ pairs can be memorably separated and transferred, which is favorable to photocatalytic efficiency. Among HCN, the HCN-3h sample has the highest H₂ generation rate of 4297.9 μmol h^?1 g^?1, which achieves 2.3-fold higher than that of GCN (1291.7 μmol h^?1 g^?1). This paper brings forward a meaningful method of boosting the photocatalytic performance of photocatalysts by constructing abundant CVs.     

Active-center-enriched Ni0.85Se/g-C3N4 S-scheme heterojunction for efficient photocatalytic H2 generation

Photocatalysts with abundant active sites are essential for photocatalytic H₂ evolution from water. Herein, Ni_0.85Se-deposited g-C₃N₄ was obtained by a physical solvent evaporation method. The investigation shows that Ni_0.85Se with unsaturated active Se atoms can significantly improve the photocatalytic activity of g-C₃N₄, and the H₂ production rate of Ni_0.85Se/g-C₃N₄ can reach 8780.3 μmol g^?1 h^?1, which is 3.5 and 92.9 times higher than that of Ni_0.85+xSe/g-C₃N₄ (2497.9 μmol g^?1 h^?1) and pure g-C₃N₄ (94.5 μmol g^?1 h^?1), respectively. This improvement can be attributed to the quick charge transfer between Ni_0.85Se and g-C₃N₄ with S-scheme heterojunction feature based on a series of trapping experiments and photoelectrochemical analysis. Moreover, abundant unsaturated Se atoms could provide more H₂ evolution active sites. This work sheds light on the construction of heterojunctions with abundant active sites for H₂ production.     

Synergistic enhancement of photocatalytic H2 production by Ni decorated 2D bubble-like carbon nitride

In this paper, a novel 2D bubble-like g-C₃N₄ (B–CN) with a highly porous and crosslinked structure is successfully synthesized via a cost-effective bottom-up process. The as-prepared B–CN photocatalyst delivers a considerably expanded specific surface area and increased active sites. Moreover, the 2D bubble-like structure can afford shortened diffusion paths for both photogenerated charge carriers and reactants. As a result, the photocatalytic H₂ evolution rate of B–CN reached 268.9 μmol g^?1 h^?1, over 5 times more than that of bulk C₃N₄. The Ni ions were further deposited on B–CN as a cocatalyst to enhance the photocatalytic activity. Benefit from the synergy of 2D bubble-like structure and Ni species cocatalyst, recombination of photoinduced charges was greatly inhibited and the hydrogen evolution reaction (HER) was significantly accelerated. The resulted catalyst achieved a dramatically high H₂ evolution rate of 1291 μmol g^?1 h^?1. This work provides an alternative way to synthesize novel porous carbon nitride together with non-noble metal cocatalysts toward enhanced photocatalytic activity for H₂ production.     

Bimetallic PtNi alloy modified 2D g-C3N4 nanosheets as an efficient cocatalyst for enhancing photocatalytic hydrogen evolution

Platinum-based alloy materials as effective cocatalysts in improving the performance of photocatalytic H₂ production have raised great interest. Herein, a facile strategy of chemical reduction is established to synthesize bimetallic PtNi nanoparticles on 2D g-C₃N₄ nanosheets with excellent photocatalytic activity. The addition of PtNi nanoparticles can provide new H⁺ reduction sites and increase more active sites of the material. The synergistic effect between PtNi alloy nanoparticles and 2D g-C₃N₄ nanosheets can regulate electronic structure, narrow the band, accelerate charge transfer efficiency and inhabit the recombination of photo-induced electron (e⁻) and hole pairs (h⁺), contributing to the improvement of hydrogen evolution activity. The optimal hydrogen evolution rate of Pt_0.6Ni_0.4/CN shows higher hydrogen evolution rate (9528 μmol·g⁻¹·h⁻¹), which is 13.1 times than that of pure g-C₃N₄ nanosheets. Besides, a possible mechanism of photocatalytic hydrogen generation has been brought up according to a series of physical and chemical characterization. This work also provides a potential idea of developing cocatalysts integrating metal alloys with 2D g-C₃N₄ nanosheets for promoting photocatalytic hydrogen evolution.     

Accelerating photocatalytic hydrogen evolution of Ta2O5/g-C3N4 via nanostructure engineering and surface assembly

Despite that several strategies have been demonstrated to be effective for improving the catalytic hydrogen evolution activity of bulky g-C₃N₄, the large-scale hydrogen production over g–C₃N₄–based photocatalysts still confronts a big challenge. Here, a two-step calcination method is presented in constructing metal oxide/two-dimensional g-C₃N₄, i.e., Ta₂O₅/2D g-C₃N₄ photocatalyst. Thanks to the superiority of the synthetic method, nanostructure engineering forming 2D structure, and surface assembly with another semiconductor, can be realized simultaneously, in which ultrathin structure of 2D g-C₃N₄ and strong interfacial coupling between two components are two important characteristics. As a result, the structure engineered Ta₂O₅/2D g-C₃N₄ induces high photocatalytic hydrogen evolution half reaction rate of ~19,000 μmol g^?1 h^?1 under visible light irradiation (λ > 400 nm), and an external quantum efficiency (EQE) of 25.18% and 12.48% at 405 nm and 420 nm. The high photocatalytic performance strongly demonstrates the advance of the synchronous engineering of nanostructure and construction of heterostructure with tight interface, both of which are beneficial for the fast charge separation and transfer.     

Graphite carbon nitride loaded nitrogen-doped carbon and cobalt nanoparticles ternary photocatalyst for enhanced solar-driven hydrogen evolution

In this paper, we designed a composite photocatalytic system in which cobalt nanoparticles (Co NPs) are attached to nitrogen-doped carbon (N-d-C) and co-bonded to the surface of the noted photocatalyst graphite carbon nitride (g-C₃N₄), showing an excellent photocatalytic hydrogen production. The bulk g-C₃N₄ was formed in the first thermal treatment in air using melamine as a precursor. Subsequently, the secondary calcination under N₂ led to the synchronous fabrication of N-d-C/Co NPs and their combination with g-C₃N₄ to form a novel ternary photocatalyst (g-C₃N₄/N-d-C/Co NPs). Co NPs exposed on the surface of the nanomaterials endowed much more reaction sites than g-C₃N₄ for photocatalytic hydrogen production. Meanwhile, the embedded N-d-C provided an additional transfer approach for photocarriers. The as-prepared composite nanomaterials own a relatively high specific surface area of 97.45 m² g^?1 with an average pore size of 3.83 nm. As a result, compared with pristine g-C₃N₄ (～25.35 μmol g^?1 h^?1), the photocatalytic performance was increased by over 10 times (～270.05 μmol g^?1 h^?1). Our work gives a novel approach for highly active g–C₃N₄–based photocatalysts in the field of photocatalysis.     

A facile one-step strategy to construct 0D/2D SnO2/g-C3N4 heterojunction photocatalyst for high-efficiency hydrogen production performance from water splitting

Fabricating 0D/2D heterojunctions is considered to be an efficient mean to improve the photocatalytic activity of g-C₃N₄, whereas their applications are usually restricted by complex preparation process. Here, the 0D/2D SnO₂/g-C₃N₄ heterojunction photocatalyst is prepared by a simple one-step polymerization strategy, in which SnO₂ nanodots in-situ grow on the surface of g-C₃N₄ nanosheets. It shows the outstanding photocatalytic H₂ production activity relative to g-C₃N₄ under the visible light, which is due to the formation of 0D/2D heterojunction significantly contributing to the separation of photogenerated charge carriers. In particular, the H₂ production rate over the optimal SnO₂/g–C₃N₄–1 sample is 1389.2 μmol h⁻¹ g⁻¹, which is 6.06 times higher than that of g-C₃N₄ (230.8 μmol h⁻¹ g⁻¹). Meanwhile, the AQE value of H₂ production over the SnO₂/g–C₃N₄–1 sample reaches up to a maximum of 4.5% at 420 nm. This work develops a simple approach to design and fabricate g–C₃N₄–based 0D/2D heterojunctions for the high-efficiency H₂ production from water splitting.     

Direct Z-scheme CoS/g-C3N4 heterojunction with NiS co-catalyst for efficient photocatalytic hydrogen generation

Facilitating the separation of photoexcited electron-hole pairs and enhancing the migration of photogenerated carriers are essential in photocatalytic reaction. CoS/g-C₃N₄/NiS ternary photocatalyst was prepared by hydrothermal and physical stirring methods. The optimized ternary composite achieved a hydrogen yield of 1.93 mmol g^?1 h^?1, 12.8 times that of bare g-C₃N₄, with an AQE of 16.4% at 420 nm. The enhanced photocatalytic activity of CoS/g-C₃N₄/NiS was mainly ascribed to the synergistic interaction between the Z-scheme heterojunction constructed by CoS and g-C₃N₄ and the NiS co-catalyst featuring a large amount of hydrogen precipitation sites, which realized the efficient separation and migration of photogenerated carriers. In addition, the CoS/g-C₃N₄/NiS heterojunction-co-catalyst system exhibited excellent photocatalytic stability and recyclability.     

In-situ synthesis of ternary heterojunctions via g-C3N4 coupling with noble-metal-free NiS and CdS with efficient visible-light-induced photocatalytic H2 evolution and mechanism insight

The two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheets based composites are prepared in the form of the NiS/g-C₃N₄, CdS/g-C₃N₄ and CdS/NiS/g-C₃N₄ using a facile and reliable method of chemical deposition. The TEM and HRTEM images demonstrated a spectacular representation of the 2D lamellar microstructure of the g-C₃N₄ with adequately attached CdS and NiS nanoparticles. The changes in crystallinity and the surface elemental valence states of composites with the incorporation of two metal sulphides are studied, which confirmed the formation of composites. The photocatalytic response of the composites was estimated by photodegradation of Rhodamine B (C₂₈H₃₁ClN₂O₃–RhB), and the ternary composite CdS/NiS/g-C₃N₄ samples exhibited the superior photocatalytic performance. Further, the free radical capture and electron paramagnetic resonance (EPR) spectroscopy experiments identified the main active species that contributed to the photocatalytic reaction. Besides, the samples’ photocatalytic performance was evaluated by photocatalytic hydrogen production. The stability of the performance-optimized composite was determined by employing cyclic experiments over five cycles. The CdS/NiS/g-C₃N₄ showed the highest efficiency of hydrogen production i.e. about 423.37 μmol.g^?1.h^?1, which is 2.89 times that of the pristine g-C₃N₄. Finally, two types of heterojunction structures were proposed to interpret the enhanced photocatalytic efficiency.     

Ag2CO3-derived Ag/g-C3N4 composite with enhanced visible-light photocatalytic activity for hydrogen production from water splitting

In this paper, Ag-based g-C₃N₄ composites have been successfully fabricated through two deferent synthetic methods: (i) a facile and efficient precipitation-calcination strategy (denoted as D–CN–xAg, x represents the dosage of Ag₂CO₃, the same below), (ii) a calcination method (denoted as Z–CN–xAg). All Ag-based g-C₃N₄ composites exhibit the enhanced photocatalytic activities under visible-light irradiation. Moreover, the optimal dosage of Ag₂CO₃ in the D–CN–xAg composite is found to be 5%, the corresponding hydrogen production capacity is 153.33 μmol g⁻¹ h⁻¹, which is 4.6 times higher than that of Z–CN–5%Ag composite. This might be attributed to appropriate content of metallic Ag and more active sites exposed on the surface of D–CN–5%Ag composite. Meanwhile, combining with photoelectrochemical results, it could be inferred that LSPR effect and the intimate interfacial between metallic Ag and g-C₃N₄ in the system play also important role for the improvement of photocatalytic activity. These results demonstrate that the appropriate loading of metallic Ag originated from Ag₂CO₃ into g-C₃N₄ could accelerate the separation and transfer of photogenerated electron-hole pairs, leading to the improvement of photocatalytic activity for hydrogen production from water splitting. Finally, a possible photocatalytic mechanism is proposed.     

Sulfur-doped 2D/3D carbon nitride-based van der Waals homojunction with superior photocatalytic hydrogen evolution and wastewater purification

The weaker van der Waals force between layers inhibits the interlayer electron migration, which greatly limiting the enhancement of the photocatalytic activity over graphitic carbon nitride (g-C₃N₄). Herein, the metal-free sulfur-doped 2D/3D van der Waals (vdW) homojunction (2D/3D CNSCN) that containing 2D sulfur-doped g-C₃N₄ nanosheets (CNS) and 3D g-C₃N₄ flower-like hierarchical structure (CN) was fabricated. Thanks to the cooperative effect of 2D-3D structural and good compatibility between CNS and CN, an in situ formed 2D/3D vdW homojunction served as the driving force for promoting charge carrier separation and transfer. The optimal photocatalytic H₂ evolution of 2D/3D CNSCN reached up to 2196 μmol h^?1g^?1, which was 4.1 and 3.2 times higher than that of CN and CNS, respectively. 10 mg of the 2D/3D CNSCN photocatalyst was able to totally remove of rhodamine B (RhB) solution in less than 80 min under the visible light. This study provides new opportunities to construct novel 2D/3D mixed-dimensional vdW homojunction, and broad interest in vdW homojunction research for the applications in energy conversion and environmental protection field.     

2D MOFs enriched g-C3N4 nanosheets for highly efficient charge separation and photocatalytic hydrogen evolution from water

Here we report a 2D-2D heterostructure of g-C₃N₄/UMOFNs photocatalysts via mechanical grinding two kinds of two-dimensional nanosheets of g-C₃N₄ nanosheets and UMOFNs, which exhibits enhanced H₂ evolution from water with simulated solar irradiation. g-C₃N₄ nanosheets are in close contact with UMOFNs, and there is a certain interaction between them, showing the effect of superimposition on the two-dimensional layer. The 2D-2D heterostructure offers a maximal photocatalytic hydrogen production activity of 1909.02 μmol g⁻¹ h⁻¹ with 3 wt% of UMOFNs, which is 3-fold higher than that of g-C₃N₄ nanosheets (628.76 μmol g⁻¹ h⁻¹) and 15-flod higher than that of bulk g-C₃N₄ (124.30 μmol g⁻¹ h⁻¹). The significant increasement of photocatalysis is due to 2D-2D heterostructure possessing a short charge transfer distance and large contact area between g-C₃N₄ and UMOFNs. The highly dispersed NiO, CoO and π-π bonds in UMOFNs of 2D-2D structure also promote charge transfer and enhance the photocatalytic activity.     

Novel ReS2/g-C3N4 heterojunction photocatalyst formed by electrostatic self-assembly with increased H2 production

Binary heterostructures (named as CN@Re) composed of ReS₂ nanospheres and g-C₃N₄ nanosheets are constructed by electrostatic self-assembly method. The ReS₂ nanospheres were prepared by hydrothermal method and the g-C₃N₄ nanosheets were treated with surface charge modification. Hydrogen production efficiency of modified CN and CN@Re nanostructures was evaluated in a simulated solar environment. To our surprise, CN5@Re5% exhibits the highest H₂ production up to 1823 μmol g^?1h^?1 of CN5@Rey, which is 3.2 times as high as CN. The improvement of the photocatalytic hydrogen production efficiency of modified CN is attributed to its interaction with the hole sacrificing agent lactic acid, while the improvement of the photocatalytic activity of CN@Re nanostructure is attributed to the efficient electron transfer efficiency between CN and ReS₂ and the enhanced light absorption capacity brought by ReS₂. In addition, the photocatalytic stability of CN5@Re5% has been studied, which can maintain a stable rate of hydrogen production over four cycles. The apparent quantum efficiency is as high as 4.10% at 365 nm and 2.82% at 420 nm.     

Fabrication of 0D/1D/2D ZnS–CuS nanodots/GNRs/g-C3N4 heterojunction photocatalyst for efficient photocatalytic overall water splitting

Photocatalytic water splitting has become a significant challenge in modern chemistry. In this process, the rate-determining step is the hydrogen evolution reaction (HER). In the present work, a surface modification approach for graphitic carbon nitride (g-C₃N₄) was applied to improve its photocatalytic HER. 0D ZnS–CuS nanodots were synthesized with the hydrothermal method as a co-catalyst to enhance the capability and stability of water splitting in the presence of visible light irradiation. Also, graphene nanoribbons were synthesized from CNTs unzipping to reduce the energy barrier of HER, improve the HE kinetic, and enhance the catalytic performance of the g-C₃N₄. By using ZnS–CuS/GNRs₍₂₎/g-C₃N₄ photocatalyst, a low onset potential of 130 mV, slight Tafel slope of 41 mV dec^?1, as well as excellent stability of 2000 s was obtained in acidic media. This efficient performance is attributed to the increased visible light absorption level in the proposed photocatalyst and the high stability in electron-hole pairs.     

High-efficiency of novel hierarchical 3D macroporous g-C3N4 material on solar-driven photocatalytic water-splitting for hydrogen evolution

The use of multi-pore nanostructured g-C₃N₄ photocatalysts is an efficient approach to separate photogenerated charge carriers and increase visible light photocatalytic performance. Recent progress has yielded nanostructured material through hard templating, which limits potential applications. Integrating the 2D building block into multidimensional porous structures remains a significant challenge in scalable production. Herein, a novel technique based on P407 bubble clusters templating and fixation by freezing is described for the first time to fabricate a 3D opened-up macroporous g-C₃N₄ nanostructures for photocatalytic H₂ evolution. Three-dimensional hierarchical nanostructures provide more contact active sites and synergistically promote the creation of heterogeneous catalytic interfaces. This feature is very useful for understanding the transfer path of photoinduced charges as well as the origins of the high charge separation efficiency in photocatalytic reactions, thus yielding a remarkable visible light-induced H₂ evolution rate of 4213.6 μmol h⁻¹ g⁻¹, which is nearly 5.6 times (716 μmol h⁻¹ g⁻¹) higher than that of lamellar bulk g-C₃N₄. This newly developed approach offers a promising alternative to synthesize broad-spectral response 3D hierarchal g-C₃N₄ nanostructures and can be extended to assemble other functional nanomaterials as building blocks into macroscopic configurations coupled with electronic modulation strategy simultaneously.     

Construction of ternary hybrid layered reduced graphene oxide supported g-C3N4-TiO2 nanocomposite and its photocatalytic hydrogen production activity

Reduced graphene oxide (rGO) supported g-C₃N₄-TiO₂ ternary hybrid layered photocatalyst was prepared via ultrasound assisted simple wet impregnation method with different mass ratios of g-C₃N₄ to TiO₂. The synthesized composite was investigated by various characterization techniques, such as XRD, FTIR, Raman Spectra, FE-SEM, HR-TEM, UV vis DRS Spectra, XPS Spectra and PL Spectra. The optical band gap of g-C₃N₄-TiO₂/rGO nanocomposite was found to be red shifted to 2.56 eV from 2.70 eV for bare g-C₃N₄. It was found that g-C₃N₄ and TiO₂ in a mass ratio of 70:30 in the g-C₃N₄-TiO₂/rGO nanocomposite, exhibits the highest hydrogen production activity of 23,143 μmol g^?1h^?1 through photocatalytic water splitting. The observed hydrogen production rate from glycerol-water mixture using g-C₃N₄-TiO₂/rGO was found to be 78 and 2.5 times higher than g-C₃N₄ (296 μmol g^?1 h^?1) and TiO₂ (11,954 μmol g^?1 h^?1), respectively. A direct contact between TiO₂ and rGO in the g-C₃N₄-TiO₂/rGO nanocomposite produces an additional 10,500 μmol g^?1h^?1 of hydrogen in 4 h of photocatalytic reaction than the direct contact between g-C₃N₄ and rGO. The enhanced photocatalytic hydrogen production activity of the resultant nanocomposite can be ascribed to the increased visible light absorption and an effective separation of photogenerated electron-hole pairs at the interface of g-C₃N₄-TiO₂/rGO nanocomposite. The effective separation and transportation of photogenerated charge carriers in the presence of rGO sheet was further confirmed by a significant quenching of photoluminescence intensity of the g-C₃N₄-TiO₂/rGO nanocomposite. The photocatalytic hydrogen production rate reported in this work is significantly higher than the previously reported work on g-C₃N₄ and TiO₂ based photocatalysts.     

Sustainable hydrogen production by CdO/exfoliated g-C3N4 via photoreforming of formaldehyde containing wastewater

Graphitic carbon nitride (g-C₃N₄) has been well-known as an appealing semiconducting material for photocatalytic hydrogen production despite its restricted active sites and poor electronic properties. In this work, exfoliated g-C₃N₄ nanosheets were synthesised by chemical treatment of the bulk graphitic carbon nitride (gCN) and the nanosheets were further doped with CdO. The photocatalysts produced were extensively characterized by diverse analysis including XRD, BET, XPS, TEM, FESEM, UV-Vis spectroscopy and PL analysis. The BET surface area of CdO/exfoliated g-C₃N₄, 40.1 m² g⁻¹ was doubled in comparison to the exfoliated g-C₃N₄. Numerous electrochemical analyses such as Mott-Schottky, linear weep voltammetry and chronoamperometry were also performed in a standard photoelectrochemical system with three-electrode cell. The hydrothermally synthesised CdO/exfoliated g-C₃N₄ resulted higher amount of hydrogen evolution (145 μmol/g) for the photoreforming of aqueous formaldehyde than the CdO (20 μmol/g), bulk gCN (58 μmol/g) and exfoliated g-C₃N₄ (87 μmol/g). The excellent hydrogen production rate using CdO/exfoliated g-C₃N₄ nanocomposite could be ascribed by higher number of active sites as well as shorter path of the charge carries to the reaction surface. The anticipated Z-Scheme mechanism has demonstrated a synergistic impact between the CdO and exfoliated g-C₃N₄ where the organic compounds acting as hole scavenger as well as contribute protons, H⁺ for the effective hydrogen production. Thus, it is clearly confirmed that the newly formulated CdO/exfoliated g-C₃N₄ has an outstanding potentiality for environmental remediation and conversion sectors.     

Hierarchical TiO2 spheroids decorated g-C3N4 nanocomposite for solar driven hydrogen production and water depollution

A novel hierarchical TiO₂ spheroids embellished with g-C₃N₄ nanosheets has been successfully developed via thermal condensation process for efficient solar-driven hydrogen evolution and water depollution photocatalyst. The photocatalytic behaviour of the as-prepared nanocomposite is experimented in water splitting and organic pollutant degradation under solar light irradiation. The optimal ratio of TiO₂ spheroids with g-C₃N₄ in the nanocomposite was found to be 1:10 and the resulting composite exhibits excellent photocatalytic hydrogen production of about 286 μmol h^?1g^?1, which is a factor of 3.4 and 2.3 times higher than that of pure TiO₂ and g-C₃N₄, respectively. The outstanding photocatalytic performance in this composite could be ascribed as an efficient electron-hole pair's separation and interfacial contact between TiO₂ spheroids with g-C₃N₄ nanosheets in the formed TiO₂/g-C₃N₄ nanocomposite. This work provide new insight for constructing an efficient Z-scheme TiO₂/g-C₃N₄ nanocomposites for solar light photocatlyst towards solar energy conversion, solar fuels and other environmental applications.     

Morphology and defects design in g-C3N4 for efficient and simultaneous visible-light photocatalytic hydrogen production and selective oxidation of benzyl alcohol

Small surface area, deficient reaction sites, and poor visible-light harvest ability of the original graphitic carbon nitride (g-C₃N₄) severely restrict its photocatalytic H₂ production activity. Here, an ultrathin porous and N vacancies rich g-C₃N₄ (V_N-UP-CN) was fabricated by thermal oxidation exfoliation and high-temperature calcination under the Ar atmosphere. The ultrathin porous morphology increases the surface area and reaction sites of original g-C₃N₄, moreover, the produced N vacancies greatly broaden the light harvest ability of ultrathin porous g-C₃N₄ (UP–CN). Therefore, V_N-UP-CN displays the maximal H₂ production rate of 2856.7 μmol g^?1 h^?1 in triethanolamine solution under visible-light, and adding 0.5 M of K₂HPO₄ can further improve its H₂ production rate to 4043.9 μmol g^?1 h^?1. Importantly, V_N-UP-CN also shows good performance in simultaneous photocatalytic H₂ production and benzyl alcohol oxidation to benzaldehyde with the activities of 196.08 and 198.28 μmol g^?1 h^?1, respectively, which avoids the waste of sacrificial agent and photogenerated holes. This work affords an achievable way to design the efficient g-C₃N₄ photocatalyst by morphology and defect regulation, which can effectively utilize both photogenerated electrons and holes for H₂ and value-added chemical production.