In-situ synthesis of novel plate-like Co(OH)2 co-catalyst decorated TiO2 nanosheets with efficient photocatalytic H2 evolution activity

Efficient separation of photo-generated electrons and holes is a crucial aspect for photocatalytic hydrogen evolution. Herein, novel plate-like Co(OH)₂ decorated TiO₂ nanosheets for photocatalytic water splitting were synthesized by a facile in-situ synthetic method. The results of X-ray diffractometry (XRD), transmission electron microscope (TEM), UV–Vis diffusion reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) indicate the successfully incorporation of Co(OH)₂ co-catalysts onto the surface of TiO₂ nanosheet photocatalysts. Further photocatalytic hydrogen evolution experiments illustrate that all Co(OH)₂ decorated TiO₂ samples show higher rate of hydrogen production performance than pure TiO₂ sample and the composite sample with Co(OH)₂ loading amount of 0.5mol% presents the highest photocatalytic hydrogen production activity of 746.93 μmol g^?1·h^?1. It is indicated that plate-like Co(OH)₂ particle act as an electron collector, which leads to photo-generated electrons transfer from TiO₂ to Co(OH)₂, and therefore enhance the photocatalytic activity. Based on above results, a possible mechanism is proposed and further verified by surface photovoltage spectra (SPV).     

Investigation of the appropriate content of graphene in AgTiO2-graphene ternary nanocomposites applied as photocatalysts

AgTiO₂-graphene ternary nanocomposites with varying graphene contents were fabricated by photocatalytic reduction. SEM and TEM imaging of the nanocomposites showed that TiO₂ nanoparticles decorated with Ag nanoparticles covered graphene nanosheets. A higher content of graphene was shown to be favorable for dye photodegradation. The results of electrochemical analysis revealed that a higher graphene content contributed to increased conductivity and reduced interfacial impedance, which led to more efficient electron transport and thus higher photocatalytic activity. The highest efficiency in dye photodegradation and hydrogen production from water splitting was achieved when the ratio of TiO₂ to graphene in the nanocomposite was 5: 1. The corresponding mass-normalized hydrogen evolution rate and quantum efficiency were 129.5 μmol g^?1 h^?1 and 4.8%, respectively. A mechanism for photocatalysis was proposed and discussed. This study demonstrates that the AgTiO₂-graphene ternary nanocomposite could be a promising photocatalyst.     

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.     

Facile synthesis and electrochemical hydrogen storage of bentonite/TiO2/Au nanocomposite

In this study, the electrochemical hydrogen storage of bentonite composites containing TiO₂ and Au nanoparticles (NPs) has been investigated by cyclic voltammetry (CV) analysis. TiO₂ NPs were first deposited on the bentonite substrate by reflux technique. Au NPs were then prepared by laser ablation in liquid (LAL) method under different laser irradiation times (6, 12, and 18 min), and utilized in the decoration of bentonite/TiO₂ nanocomposite by physical mixing. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and elemental mapping were carried out in the characterization of the prepared bentonite/TiO₂/Au nanocomposite. The surface and chemical properties of the acquired nanocomposite were analyzed by Brunauer-Emmett-Teller and Fourier transform infrared spectroscopy, respectively. Electrochemical measurement was performed on stainless steel mesh prefabricated electrodes in 1 M KOH electrolyte solution. The B-T/Au nanocomposite prepared under 12 min laser irradiation displayed the highest hydrogen storage capacity (15 Cg^-1).     

Highly stabilized Ag2O-loaded nano TiO2 for hydrogen production from glycerol: Water mixtures under solar light irradiation

Nano TiO₂ prepared by a hydrothermal method and silver-loaded nano TiO₂ prepared by impregnation were studied for the photocatalytic production of hydrogen from glycerol:water mixtures. The structural characteristics were revealed using XRD, EDAX, DRS, TEM, XPS, BET surface area and Raman techniques. The photocatalytic hydrogen production has been investigated under solar light irradiation. Effects of nano TiO₂ calcination temperature, silver loading, photocatalyst content, light source and Ag oxidation state on hydrogen production have been systematically studied. Maximum hydrogen production of 200 μmol h^?1 g^?1 is observed on 4wt% silver-loaded nano TiO₂ catalyst in pure water and the maximum hydrogen production of 7030 μmol h^?1 g^?1 is observed on 3wt% silver-loaded nano TiO₂ catalyst in glycerol: water mixtures. Silver-loaded nano TiO₂ reduced and photodeposited catalysts show similar hydrogen production activities in glycerol: water mixtures under solar irradiation. The optimum catalyst modified with conducting carbon materials (graphene oxide, graphene, carbon nanotubes) by a solid-state dispersion method were also studied for hydrogen production under solar light irradiation. Compared with pure nano TiO₂, a 3wt% silver-loaded nano TiO₂/graphene composite exhibited an approximately 17-fold enhancement of hydrogen production leading to hydrogen production rates of 12,100 μmol h^?1 g^?1. Based on the characterization results and hydrogen production activity on these catalysts, a structure–activity correlation has been proposed wherein the interacting Ag₂OAg phases on the surface of nano TiO₂ play an important role in maintaining a high hydrogen production activity under solar irradiation.     

Enhanced photoelectrochemical water splitting in hierarchical porous ZnO/Reduced graphene oxide nanocomposite synthesized by sol-gel method

Today the utilization of solar energy to split water and its conversion to hydrogen and oxygen has been considered as a powerful way to solve the environmental crisis. Hierarchical porous nanostructured ZnO and ZnO/reduced graphene oxide (rGO) composite photoanodes are synthesized by innovated sol-gel method using triethylenetetramine (TETA) as a stabilizer. The hierarchical porous ZnO structure containing large agglomerates each consisting of tiny nanoparticles are formed. The X-ray diffraction analysis and Raman spectroscopy confirm the in-situ reduction of graphene oxide sheets during synthesis and formation of ZnO/rGO nanocomposite. Although the band gap and transmittance of the porous nanocomposites do not dramatically change by rGO addition, the main photoluminescence peak quenches entirely showing prolonging exciton lifetime. The ZnO/rGO porous structure achieved remarkably improved current density (1.02 mA cm^?2 at 1.5 V vs. Ag/AgCl) in 1 wt% rGO, up to 12 times higher compared to the bare ZnO (0.09 mA cm^?2 at 1.5 V vs. Ag/AgCl), which attributes to positive role of ZnO hierarchical porous structure and rGO electron separation/transportation. These findings provide new insights into the broad applicability of this methodology for promising future semiconductor/graphene composite in the field of photoelectrochemical water splitting.     

Facile synthesis of Ti3+ doped Ag/AgITiO2 nanoparticles with efficient visible-light photocatalytic activity

We successfully synthesized novel Ti³⁺ doped TiO₂ and Ti³⁺ doped Ag/AgITiO₂ nanoparticles with efficient visible-light photocatalytic activity for hydrogen production by facile one-step solvothermal method. The as-prepared Ti³⁺ doped TiO₂ nanoparticles displayed excellent visible-light absorption and visible-light driven hydrogen production activity (115.3 μmol g^?1 h^?1), while the commercial TiO₂ had no visible-light response. Moreover, the as-prepared Ti³⁺ doped Ag/AgITiO₂ nanoparticles in this experiment showed highly enhanced visible-light absorption and efficient visible-light driven activity for hydrogen (571.0 μmol g^?1 h^?1), which was 4.95 times as high as that of the as-prepared TiO₂ nanoparticles. And the surface areas of the as-prepared TiO₂ and Ti³⁺ doped Ag/AgITiO₂ catalysts were up to 138.829 m² g^?1 and 102.988 m² g^?1, much higher than that of the commercial TiO₂ (55.516 m² g^?1). Finally, the visible-light photocatalytic mechanism of the Ti³⁺ doped Ag/AgITiO₂ nanoparticles for hydrogen generation was also proposed in detail.     

A ternary Ag/TiO2/CNT photoanode for efficient photoelectrochemical water splitting under visible light irradiation

A ternary Ag/TiO₂/CNT photoanode was prepared by grafting Ag nanoparticles on the surface of as-synthesized TiO₂/CNT nanocomposite for the photoelectrochemical (PEC) water splitting under visible light irradiance. The ternary composite photoanode was observed to generate four times higher photocurrent density compared to binary TiO₂/CNT nanocomposite under visible light irradiance. The Ag nanoparticles on the surface of nanocomposite act as a surface plasmon resonance (SPR) photosensitizer under visible light. The enhanced photocurrent density of Ag/TiO₂/CNT ternary photoanode is attributed to the increased light absorption in the visible region, decrease in band-bending and effective interfacial electron transfer due to the synergetic effect of Ag nanoparticles and CNTs. The enhanced charge transfer within the Ag/TiO₂/CNT was also confirmed by the electrochemical impedance spectroscopy. This work demonstrates a feasible route to improve the PEC performance of TiO₂ towards water splitting under sunlight irradiation.     

A triptych photocatalyst based on the Co-Integration of Ag nanoparticles and carbo-benzene dye into a TiO2 thin film

This work proposes a new efficient, long-lasting scalable and low-cost triptych photocatalyst by assembling a semiconductor thin film (planar anatase TiO₂), a photosensitive molecule of the carbo-benzene (Cbz) family and plasmonic Ag nanoparticles with exquisite degree of intimacy with the semiconductor. Under simulated sunlight conditions over 48 h, the triptych TiO₂/Ag/Cbz photocatalyst allows a hydrogen production rate of 0.18 mmol g_{photocatalyst}⁻¹ h⁻¹ in conditions of applicative pressure (2.2 bars) and temperature (ambient) suitable for commercial applications. A ternary synergy (~33%) for hydrogen production is clearly evidenced with the triptych material in comparison with the diptych counterpart.The role of each component (TiO₂, Ag and Cbz) on the H₂ production is investigated systematically by discriminating the light absorption from the different materials and interfaces. We show how to achieve an efficient vertical Schottky junction between Ag nanoparticles and the TiO₂ substrate that is demonstrated to be of crucial importance in the water-splitting process.     

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.     

Hydrogen adsorption properties of Ag decorated TiO2 nanomaterials

In this work, we present the synthesis of Ag doped TiO₂ materials. The products are characterized by powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption, and hydrogen adsorption. The Ag/TiO₂ materials exhibit 3.65 times higher in hydrogen adsorption capability compared with the non-doped TiO₂ materials thank to the existence of Ti³⁺ species, which are Kubas-type hydrogen adsorption centers, and the Ag nanoparticles which provide spillover effects. We believe that this is the first time that both Kubas-type adsorption and spillover are exploited in the design of novel hydrogen storage materials.     

Nickel-cobalt layered double hydroxide ultrathin nanosheets coated on reduced graphene oxide nonosheets/nickel foam for high performance asymmetric supercapacitors

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett and Teller (BET) and electrochemical techniques such as voltammetry (CV), galvanostatic charge-discharge curves (GCD) and electrochemical impedance spectroscopy (EIS). The resulting electrode which prepared in the presence of CTAB afforded extremely high specific capacitance of 2133.3 F g^?1 at a current density of 4 A g^?1. FE-SEM, TEM and EDS mapping results showed that Ni-Co LDH nanosheets uniformly covered the surface of rGO/NF in the presence of CTAB, and is closely packed and thinner in thickness compared with the sample prepared in similar way without using surfactant. Such new thin and dense morphology facilitates electrolyte ions diffusion through the prepared electrode. A good cycling stability was obtained for the electrode in alkaline media. EIS measurements showed low values of internal resistance (R_s) and charge transfer resistance (R_ct), indicating that the prepared nanocomposite is a promising candidate for supercapacitor applications. The asymmetric supercapacitor (ASC) based on the Ni-Co LDH/CTAB/rGO/NF as a positive electrode and rGO/NF as a negative electrode was assembled and it exhibited a C_s of 71.4 F g^?1 at a current density of 2 A/g and correspondingly energy density of as high as 68 Wh kg^?1.     

Syngas production by electrocatalytic reduction of CO2 using Ag-decorated TiO2 nanotubes

Huge efforts have been done in the last years on electrochemical and photoelectrochemical reduction of CO₂ to offer a sustainable route to recycle CO₂. A promising route is to electrochemically reduce CO₂ into CO which, by combination with hydrogen, can be used as a feedstock to different added-value products or fuels. Herein, perpendicular oriented TiO₂ nanotubes (NTs) on the electrode plate were grown by anodic oxidation of titanium substrate and then decorated by a low loading of silver nanoparticles deposited by sputtering (i.e. Ag/TiO₂ NTs). Due to their quasi one-dimensional arrangement, TiO₂ NTs are able to provide higher surface area for Ag adhesion and superior electron transport properties than other Ti substrates (e.g. Ti foil and TiO₂ nanoparticles), as confirmed by electrochemical (CV, EIS, electrochemical active surface area) and chemical/morphological analysis (FESEM, TEM, EDS). These characteristics together with the role of the TiO₂ NTs to enhance the stability of CO₂^·- intermediate formed due to titania redox couple (Ti^IV/Ti^III) lead to an improvement of the CO production in the Ag/TiO₂ NTs electrodes. Particular attention has been devoted to reduce the loading of noble metal in the electrode(14.5 %w/%w) and to increase the catalysts active surface area in order to decrease the required overpotential.     

TiO2 nanoparticles modified with 2D MoSe2 for enhanced photocatalytic activity on hydrogen evolution

As an emerging two-dimensional (2D) nanomaterial, 2D MoSe₂ nanosheets has the advantages of wide light response and rapid charge migration ability. In this work, 2D MoSe₂/TiO₂ nanocomposites were successfully synthesized through a simple hydrothermal method. The microstructure and photocatalytic activity of the nanocomposites were systematically investigated and determined. The corresponding Raman peaks and crystal planes of MoSe₂ were analysed by Raman spectroscopy and transmission electron microscopy respectively, demonstrating the successful combination of the MoSe₂ nanosheets and TiO₂ nanoparticles. UV-vis diffused reflectance spectra demonstrated that the introduction of MoSe₂ did increase the light absorption ability of the nanocomposites. A lower recombination of electrons and holes was demonstrated for the MoSe₂/TiO₂ heterojunction from photoluminescence results. The photocatalytic hydrogen evolution test showed that the hydrogen production rate was 4.9 μmol h⁻¹ for the sample with 0.1 wt.% MoSe₂, 2 times higher than that of bare TiO₂. This work provides a novel strategy for improving the photocatalytic properties of semiconductor photocatalyst.     

Surface modification of aligned TiO2 nanotubes by Cu2O nanoparticles and their enhanced photo electrochemical properties and hydrogen generation application

In this work, we report the synthesis of cuprous oxide (Cu₂O) nanoparticles modified vertically oriented aligned titanium dioxide (TiO₂) nanotube arrays through wet chemical treatment of TiO₂ nanotubes and their multi-functional application as enhanced photo electrochemical and hydrogen generation. The synthesized samples were characterized by X-ray diffraction, SEM, TEM, and UV–Vis spectroscopy. The structural characterization revealed that the admixed Cu₂O nanoparticles on the TiO₂ surface did not alter its crystalline structure of vertically oriented aligned TiO₂ nanotube. The photocatalytic performance and hydrogen generation of as synthesized Cu₂O nanoparticles modified aligned TiO₂ nanotube was found to highly depend on the Cu₂O content. The optical characterizations reveal that the presence of Cu₂O nanoparticles extends its absorption into the visible region which improves the photocurrent density in comparison to pristine aligned TiO₂ nanotubes electrodes due to enhanced photoactivity and better charge separation. The optimum photocurrent density and hydrogen generation rate has been found to be 3.4 mA cm^?2 and 127.5 μmole cm^?2 h^?1 in 1 M Na₂SO₄ electrolyte solution under 1.5 AM solar irradiance of white light with illumination intensity of 100 mW cm^?2.     

Enhanced photocatalytic activity in water splitting for hydrogen generation by using TiO2 coated carbon fiber with high reusability

In this study, TiO₂ coated carbon fiber (TiO₂@CF) was synthesized and used for the improvement of hydrogen (H₂) evolution. Obtained results from scanning electron microscopy (SEM), X-ray diffraction (XRD), gas adsorption analysis (BET), UV–vis diffuse (UV–vis), and X-ray photoelectron spectroscopy (XPS) confirmed that the surface area and light absorption of the material was significantly improved. The synthesized TiO₂@CF photocatalyst exhibited improved photocatalytic performance toward hydrogen generation. The enhancement of photocatalytic H₂ evolution capacity by TiO₂@CF was ascribed to its narrowed bandgap energy (2.76eV) and minimized recombination of photogenerated electron-hole pairs The hydrogen production rate by the TiO₂@CF reached 3.238 mmolg^?1h^?1, which was 4.8 times higher than unmodified TiO₂ (0.674 mmolg^?1h^?1). The synthesized TiO₂@CF was relatively stable with no distinct reduction in photocatalytic activity after five recycling runs. The photoluminescence and photocurrent were employed to support the photocatalytic H₂ production mechanism proposed mechanism.Based on these results, TiO₂@CF with unique properties, easy handle, and high reusability could be suggested as an efficient strategy to develop a high-performance photocatalyst for H₂ production.     

Photo-induced CO2 reduction by hydrogen for selective CO evolution in a dynamic monolith photoreactor loaded with Ag-modified TiO2 nanocatalyst

Ag-promoted TiO₂ nanoparticles immobilized over the cordierite monolithic support for dynamic and selective photo-reduction of CO₂ to CO by the use of hydrogen has been investigated. Ag-loaded TiO₂ NPs synthesized by a facile sol–gel method were coated over the monolith channels by dip-coating method. The samples were characterized by XRD, Raman, FTIR, SEM, TEM, XPS, N₂ adsorption–desorption, UV–Vis and PL spectroscopy. The photo-activity test of Ag-modified TiO₂ NPs was conducted for dynamic photocatalytic CO₂ reduction with H₂ as a reductant via a reverse water gas shift (RWGS) reaction in a cell type and monolith photo-reactors. Using 5 wt. % Ag/TO₂ NPs, CO₂ was energetically converted to CO with a yield rate 1335 μmole g-catal.^?1 h^?1, a 111 fold-higher than the amount of CO produced over the pure TiO₂ catalyst. More importantly, photo-activity of Ag/TiO₂ catalyst for CO evolution can be improved by 209 fold using monolith photo-reactor than the cell type reactor under the same operating conditions. This enactment was evidently due to the efficient light harvesting with larger illuminated surface area inside monolith micro-channels and efficient charges separation in the presence of Ag-metal. The reusability of Ag/TiO₂ NPs loaded over the monolithic support showed favorable recycling capability than the catalyst dispersed in a cell reactor. A possible reaction mechanism for this observation has been discussed in detail.     

Kinetic performance of TiO2/Pt/reduced graphene oxide composites in the photocatalytic hydrogen production

Among the different alternatives to generate hydrogen, photocatalysis can play an important role since it is based on the use of solar radiation and a suitable semiconductor. Starting from the most commonly researched TiO₂ catalyst, many efforts have been devoted to improve its efficacy. This work, based on the potential of reduced graphene oxide (rGO) to carry charges and platinum nanoparticles to act as efficient traps for photogenerated electrons, assesses the performance of synthesized binary and ternary photocatalysts (TiO₂/rGO, TiO₂/Pt and TiO₂/rGO/Pt) for hydrogen generation. The addition of rGO to TiO₂ almost duplicates (1.95 factor) the hydrogen production rate compared to bare TiO₂. Moreover, the binary TiO₂/Pt photocatalyst reported the best performance, with an increase in the hydrogen production rate by a factor of 15.26 compared to TiO₂. However, the ternary catalyst performed worse than the binary TiO₂/Pt probably due to the use of non-optimized co-catalyst ratios. Since the addition of rGO reduces the cost of the catalyst, the trade-off between the catalyst performance and cost is worth of future research.     

Nanostructured Bi2O3@TiO2 photocatalyst for enhanced hydrogen production

Here we report on Bi₂O₃ clusters immobilized on anatase TiO₂ nanostructures for an enhanced rate of photocatalytic H₂ evolution. Structural, morphological, and optical properties of the Bi₂O₃@TiO₂ nanocomposite (BT) were characterized by a series of techniques including X-ray diffraction, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy and electrochemical impedance spectroscopy. The catalytic H₂ evolution experiments were carried out under different light sources: natural solar light, LED UV (365 ± 5 nm) and LED visible (420 ± 5 nm) light source. Under the solar light a pristine anatase TiO₂ nanostructured (TNS) catalyst generated 4.20 mmol h^?1 g^?1, whereas in the presence of Bi₂O₃@TNS showed much higher H₂ production 26.02 mmol h^?1 g^?1. The photocatalytic activity of the BT and its reproducible performance for five recycles is ascribed to an efficient separation of photogenerated charge carriers. A plausible reaction mechanism for the H₂ generation is proposed.     

A facile dissolution strategy facilitated by H2SO4 to fabricate a 2D metal-free g-C3N4/rGO heterojunction for efficient photocatalytic H2 production

A 2D g-C₃N₄(pPCN)/rGO heterojunction for photocatalytic hydrogen production is fabricated by a facile dissolution strategy facilitated by H₂SO₄. The bulk g-C₃N₄ (CN) can be directly exfoliated into ultrathin protonated g-C₃N₄ (PCN) nanosheets under the assistance of H₂SO₄, and PCN can be further modified by rGO in a dissolved state under the electrostatic self-assembly process. The nanocomposite exhibits a large surface area (146.47 m²/g) and intimate contact interfaces between pPCN and rGO due to the specific synthesis method. Based on the DRS, PL and photoelectrochemical analyses, the introduction of rGO can greatly improve the light absorption and photogenerated charge carrier separation and transfer of g-C₃N₄. The optimal pPCN/2 wt% rGO nanocomposite shows an efficient photocatalytic H₂ evolution rate of 715 μmol g^?1 h^?1 under visible light irradiation, which is 2.6 and 13 times higher than those obtained on pPCN and CN. In addition, a photocatalytic mechanism over a 2D pPCN/rGO heterojunction is proposed. This work offers a new effective strategy for fascinating gC₃N₄based nanocomposites with promising hydrogen generation.