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This study developed an efficient photocatalyst for hydrogen production, consisting of CdS nanorods and the CoTPPBr4 co-catalyst. The synthesized photocatalyst was characterized using a suite of techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Additionally, transient photocurrent response and electrochemical impedance spectroscopy (EIS) were carried out to further probe the material's properties. Our findings demonstrate that the CoTPPBr4 co-catalyst significantly enhances the photocatalytic H2 evolution efficiency under visible light irradiation. Notably, among the tested photocatalysts, a 12.5% CoTPPBr4/CdS composite exhibited the most superior photocatalytic performance, achieving a hydrogen production rate of 41.3 mmol g−1 h−1, which is 4.1 times higher than that of pristine CdS. The introduction of CoTPPBr4 effectively facilitates charge transfer within CdS, enhances the separation efficiency of light-induced electron–hole pairs, and boosts the surface H2-evolution kinetics. This research not only introduces a promising photocatalyst for visible light-driven hydrogen production but also provides a way for the development of highly efficient and stable CdS-based hybrid semiconductor nanocomposites suitable for diverse photocatalytic applications. [ABSTRACT FROM AUTHOR]

The development of high-efficiency and low-cost photocatalysts for hydrogen production reactions is very important to solve energy problems. In this paper we study the photocatalytic H2 evolution activity of a CeO2/CoS2 heterojunction catalyst under visible light. Characterization studies such as XRD and XPS proved the successful synthesis of a CeO2/CoS2 catalyst. The composite catalyst with a CeO2 and CoS2 mass ratio of 1 : 20 had the best activity, and the hydrogen evolution rate reached 5172.20 μmol g−1 h−1. BET and UV-Vis DRS characterization showed that the introduction of CeO2 not only increased the specific surface area of the composite catalyst, but also improved the response of the photocatalyst to visible light. In addition, PL and electrochemical experiments showed that the electrons and holes of the CeO2/CoS2 catalyst could be quickly separated and transferred, thereby accelerating the kinetics of the hydrogen evolution reaction. This work provided an experimental basis for designing a composite photocatalyst with high stability and hydrogen production activity. [ABSTRACT FROM AUTHOR]

Solar-driven photocatalytic hydrogen generation via splitting water requires an efficient visible light active photocatalyst. In this work, Ni cocatalysts on a TiO2 composite photocatalyst with different graphene oxide (GO) contents were prepared using a hydrothermal method and characterized by TEM, XRD, UV-vis, Raman and PL spectra. The results show that the synthesized TiO2/GO/Ni nanosheet composites have a large specific surface area and can provide a large number of active sites for a photocatalytic hydrogen production reaction. GO can broaden the optical absorption range of TiO2 and absorb more visible light, thus stimulating more photogenerated electron–hole pairs. At the same time, GO can collect electrons and promote the separation of photogenerated electron–hole pairs. Ni, as a cocatalyst, can be used as an active site for hydrogen ion adsorption, which is conducive to promoting the migration of photogenerated electrons in the system and prolonging the life of photogenerated electrons and holes, thus ensuring the high efficiency of the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

Realizing highly efficient utilization of solar energy for solving problems of environmental pollution and energy shortage has attracted increasing attention. Herein, Z-scheme two-dimensional (2D)/2D NiCo-LDH/g-C3N4 (LDH/CN) heterojunction composites were synthesized, which showed enhanced photocatalytic performance for tetracycline hydrochloride (TC) degradation and hydrogen (H2) generation under visible light irradiation. A 2D/2D heterojunction structure was formed between NiCo-LDH nanosheets (LDH) and g-C3N4 (CN), which was beneficial for the effective separation of photogenerated charge carriers. The active species of hydroxyl (˙OH), superoxide (˙O2−) and hole (h+) radicals contributed to TC photodegradation. The optimum photocatalyst showed a remarkably enhanced photocatalytic capability with a hydrogen generation rate of 451.7 μmol g−1 h−1. The improved photocatalytic activities may be attributed to the synergistic effects of the increased absorption of visible light, the separation efficiency of carriers and the 2D/2D heterostructure. A Z-scheme photocatalytic mechanism was proposed for the LDH/CN composite, showing dual advantages of a high redox ability and efficient charge carrier separation. [ABSTRACT FROM AUTHOR]

Introducing the photothermal effect to promote the photocatalytic H2 rate is a good strategy and is gradually gaining attention. In this work, a series of ultrathin Bi2Se3/CdS nanocomposites were prepared by hydrothermal method and in situ precipitation method. Notably, CdS nanoparticles are monodispersed on the surface and aggregated at the edge of ultrathin Bi2Se3 nanosheets, as shown by the TEM images, implying the formation of a tight interface and rich active sites with a large area. As expected, the composite displays an excellent photocatalytic H2 rate under visible light irradiation, which is about 3.2 times higher than that of pristine CdS. The DRS analysis shows that Bi2Se3 endowed the Bi2Se3/CdS composite with a stronger absorption ability and a wider visible absorption range. The PL, SPV, and electrochemical tests all demonstrate that the transfer and separation of electron–holes are greatly enhanced. Furthermore, the composite exhibits good solar-to-heat conversion efficiency under full-spectrum light illumination, which is beneficial to the charge activation and transfer rate. Based on the obtained band structure, the superior photocatalytic ability of the Bi2Se3/CdS composite is ascribed to the synergetic effect of the heterojunction and the strong solar-to-heat conversion. The work provides a strategy for employing photothermal conversion to improve solar energy conversion. [ABSTRACT FROM AUTHOR]

The study of environmentally friendly semiconductor photocatalysts has important practical significance for efficient photocatalytic hydrogen evolution. In this experiment, type II heterojunction NiCo-LDH/CeO2 was prepared by in situ loading, and the NiCo-LDH/CeO2 catalyst showed good activity under simulated sunlight irradiation. Under simulated visible light irradiation, its hydrogen production rate reached 2.7 mmol h−1 g−1, which was higher than that of NiCo-LDH (0.86 mmol h−1 g−1). Through a series of characterization data, it can be concluded that the heterojunction successfully constructed by the close contact between NiCo-LDH and CeO2 accelerates the separation of photogenerated electrons and holes and can effectively inhibit the recombination of the two so that more electrons are involved in the hydrogen evolution reaction. The material has good interfacial charge transfer performance, which improves the photocatalytic performance. This work can provide an effective method for the research and development of NiCo-LDH. [ABSTRACT FROM AUTHOR]

The application of electron-accumulation sites in the photocatalytic splitting of water for the hydrogen-production process represents a prospective strategy for the efficient use of solar energy. Herein, electron-accumulation sites (Ti–Mn–O3) anchored on TiO2 hollow spheres (THS) were facilely prepared by a two-step calcination method involving the modification of Mn species and surface oxygen vacancies (Ovs). The optimized photocatalyst (TM30) showed excellent activity for photocatalytic water splitting (λ ≥ 420 nm). The Ti–Mn–O3 sites that were constructed on the surface of THS owing to electron transfer from the Mn atom to the Ti atom and three O atoms around Ovs were rich in electrons under in situ visible-light-driven conditions and constituted electron-accumulation sites, which not only greatly regulated the surface potential and band gap to enhance the separation efficiency of photogenerated charge carriers and the visible-light-responsive capability of the compound, but also improved the dissociation for the adsorption of H2O to reduce Gibbs free energies for hydrogen adsorption as well. This study demonstrates a novel approach for the efficient use of solar energy to produce hydrogen toward water splitting. [ABSTRACT FROM AUTHOR]

The substitution of C for N in graphitic carbon nitride (g-C3N4) can promote π-electron availability and increase photocatalytic activity, but the low specific surface area still limits its performance. Herein, porous C-doped g-C3N4 was prepared by the uracil-mediated supramolecular assembly of melamine and cyanuric acid. The as-prepared catalyst exhibited a high photocatalytic hydrogen evolution rate of 2352 μmol g−1 h−1 under visible light irradiation (λ ≥ 420 nm), which was 28 times that of g-C3N4 (83 μmol g−1 h−1), due to the porous architecture and C-doping effect. The porous architecture endowed the catalyst with a large specific surface area (79.4 m2 g−1) and great light utilization efficiency in the visible light region between 500 and 750 nm. In addition, C-doping modified the energy band structure of g-C3N4 to a narrow band gap (from 2.92 eV to 2.78 eV) and enhanced the separation efficiency of photogenerated carriers. [ABSTRACT FROM AUTHOR]

Herein we have demonstrated the synthesis of nitrogen vacancy enriched exfoliated B-doped g-C3N4 (e-BCN) through a facile thermal exfoliation method, characterized it using different analytical techniques and compared its photocatalytic activity with that of bulk B-doped g-C3N4 (BCN). The decrease in peak intensity and slight shift of the 2 value in the PXRD patterns confirmed the successful exfoliation of bulk BCN to an e-BCN nanosheet. FESEM and HRTEM images also indicated the formation of a thin layered nanosheet of e-BCN as compared to bulk BCN. The PL and EIS data suggested the reduced recombination rate and superior separation capability of the photo-generated charge carriers of e-BCN. The introduction of nitrogen vacancies on the surface of e-BCN is confirmed by the FTIR and XPS analyses. The increased photocurrent density of 524 μA cm−2 displayed by e-BCN indicated the better availability of photo-generated electrons due to the higher separation of charge carriers than in the bulk BCN. The as-prepared e-BCN nanosheet exhibited enhanced photocatalytic performance 1.2 and 3.7 fold greater than that of bulk BCN towards ciprofloxacin degradation and H2 generation, respectively, under visible light irradiation. The excellent photocatalytic behavior of e-BCN was ascribed to the augmented active sites with reduced recombination efficiency and increased separation ability of the photo-induced e−/h+ pairs of the e-BCN nanosheet. This work suggested the facile fabrication of e-BCN through the thermal exfoliation process and its photocatalytic activity towards pollutant degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

The construction of heterojunctions can effectively improve the electron transport rate and photocatalytic activity. In this work, nanoflower-like S-scheme heterojunction MoS2/NiAl-LDH was successfully synthesized. The results indicated that the hydrogen yield of the MoS2/NiAl-LDH composite catalyst reached 229.5 μmol in 5 hours under visible light irradiation by adjusting the pH value of the sacrificial agent and the amount of eosin. The crystal structure and morphological characteristics of the composite were analyzed by XRD, SEM and TEM. The visible light response degree and charge separation and transfer rates of photogenerated carriers of the composite were analyzed by UV-Vis DRS, PL and electrochemistry. The electronic transfer path was also analyzed by XPS. The construction of S-scheme heterojunctions can realize effective separation of electron–hole pairs and ensure that the photo-induced carriers with the strongest redox ability can be retained to participate in the photocatalytic reaction. In addition, the feasible mechanism of photocatalytic hydrogen evolution is given. This work will provide different insights into the enhancement of hydrogen evolution by heterojunctions formed by binary semiconductors. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs), as an environmentally friendly non-noble metal cocatalyst, play a key role in promoting photocatalytic hydrogen evolution. In this work, three metal phosphating compounds (NiCoP, Ni2P, and Co2P) were synthesized by solvothermal method using red phosphorus as a phosphorus source. The three kinds of co-catalysts were individually loaded onto Zn0.5Cd0.5S by physical agitation method to form binary nanocomposites (ZnCdS/TMPs). The results showed that the three composite photocatalysts all showed excellent HER performance in the Na2S/Na2SO3 sacrifice solution. Among them, the hydrogen production rate of ZnCdS/NiCoP-5% reached 64 μmol at 5 h, which was significantly higher than that of pure Zn0.5Cd0.5S, ZnCdS/Ni2P-5%, and ZnCdS/Co2P-5%. According to the results of various characterization techniques, NiCoP nanoparticles provide more active sites for Zn0.5Cd0.5S and the composite photocatalytic materials exhibit excellent hydrogen evolution performance. Moreover, the Schottky barrier between Zn0.5Cd0.5S and NiCoP nanoparticles effectively enhances the charge separation rate, thus promoting the improvement of photocatalytic hydrogen evolution. Therefore, low-cost transition metal phosphide as a cocatalyst has broad prospects in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

A porous Cu2O/TiO2 hybrid photocatalyst with n-type Cu2O decorated on the mesoporous TiO2 derived from MIL-125 was designed through the in situ Cu2+ ion reduction strategy. Under UV-vis light irradiation, the Cu2O/TiO2 composite with 4.2 wt% of Cu2O displayed the highest hydrogen evolution rate of 14.39 mmol h−1 g−1, which was about 9.6 and 24.8 times that of the original mesoporous TiO2 and pure Cu2O, respectively. The enhancement in photocatalytic activity can be mainly attributed to the type-I band structure formed, which can efficiently enhance the photoexcited charge carrier mobility across the phase interfaces of the Cu2O/TiO2 composite, as evidenced by the UV-DRS spectra, Mott–Schottky curves, and XPS analysis. Besides, the narrow band gap of Cu2O, conducive to the absorption of visible light, and the high specific surface of TiO2 were also found to contribute to the photoactivity enhancement. This work will provide a new perspective for the study of type-I photocatalysts. [ABSTRACT FROM AUTHOR]