Biomimetic photocatalysis inspired by nitrogenase is a promising approach to nitrogen fixation. Success in this strategy relies on the multi-metal synergistic active sites and efficient charge separation. In this study, a cascaded CN/MoFeTiO S-scheme heterojunction photocatalyst was constructed by modifying a ternary MoO3/Fe2O3/TiO2 (MoFeTiO) with g-C3N4. The optimal 0.05CN/MoFeTiO achieved an outstanding ammonia production rate of 760.5 mu mol g-1 h-1, which is 2.7 and 42.5 times higher than that of individual MoFeTiO and g-C3N4, respectively, outperforming many previously reported photocatalysts. Moreover, the corresponding apparent quantum efficiency (AQY) reached 4.1 % at 450 nm, highlighting its excellent utilization of visible light. Joint experimental and theoretical studies confirm that the constructed cascaded S-scheme heterojunction efficiently separates charge carriers, while the multi-metal (Mo/Fe/Ti) sites synergistically lower the energy barriers for N---N bond activation and NH3 desorption, thereby boosting the overall nitrogen fixation efficiency. This work provides a viable paradigm for designing high-performance nitrogen-fixing photocatalysts through a strategy that integrates biomimetic multi-site design with heterojunction engineering.

Microorganisms serve as biological factories for the synthesis of nanomaterials such as CdS quantum dots. Based on the uniqueness of Acidithiobacillus sp., a one-step route was explored to directly convert cadmium waste into CdS QDs using these bacteria. First, an exhaustive study was conducted to reveal the specific pathways involved in the biosynthesis of CdS QDs. The widely known homologous enzyme, cysteine desulfhydrase, which catalyzes the synthesis of CdS QDs from a cysteine substrate, is also present in Acidithiobacillus sp. and is referred to as the OSH enzyme. The structure of the OSH enzyme was determined through X-ray crystallography. Moreover, we identified two new pathways. One involved the SQR enzyme in Acidithiobacillus sp., which catalyzed the formation of sulfur globules and subsequently catalyzed further reactions with GSH to release H2S; subsequently, a CdS QD biosynthesis pathway was successfully constructed. The other pathway involved extracellular polyphosphate, a bacterial metabolic product, which with the addition of GSH and Cd2+, resulted in the formation of water-soluble fluorescent CdS QDs in the supernatant. Based on the above-described mechanism, after the bioleaching of Cd2+ from cadmium waste by Acidithiobacillus sp., CdS QDs were directly obtained from the bacterial culture supernatants. This work provides important insights into cleaner production and cadmium bioremediation with potential industrial applications.

Biomass flow fuel cells (BFFCs) are effective energy conversion technologies for converting biomass into electricity to realize a sustainable society. However, most of them depend on the thermal degradation of biomass, which is energy consumption and induces biomass polycondensation. Herein, we develop a novel solar-driven BFFC for converting lignin into electricity under sunlight at room temperature based on FeCl3/TiO2 synergetic mediators, which endow a broad photo-absorption range and enhance absorption intensity for high photo-catalytic activity. A new electron transfer chain is constructed by employing Fe3+ to obtain electrons and efficiently promote electron-hole separation of TiO2. Meantime, the generated & sdot;OH can depolymerize lignin rapidly. The BFFC achieved a power density of 64.4 mW/cm2 at room temperature via sunlight irradiation with sodium lignosulfonate as fuel when paired with VO2+/VO2+ catholyte. It can stably discharge and power LED light successfully. This work provides a sustainable and energy conservation approach for developing advanced biomass fuel cells.

Developing efficient catalysts for photocatalytic hydrogen evolution and pollutant degradation is one of the most ideal methods to address energy and environmental pollution issues. To address the challenges of energy crisis and environmental issues, a hollow spherical g-C3N4/Mn0.25Cd0.75S (HCNS/MCS) heterostructure was constructed and characterized. The unique morphology and appropriate band gap of the hollow carbon nitride sphere (HCNS) make it a promising photocatalytic material. The growth of Mn0.25Cd0.75S solid solution on HCNS enhances the spatial separation of photo-generated charges at the HCNS/MCS interface, thereby promoting electron transfer and reaction kinetics. Under visible light irradiation, the HCNS/MCS exhibited the highest H-2 production activity (31.34 mmol center dot g(-1)center dot h(-1)), which was 2.8 times that of pure MCS and 224 times that of pure HCNS. Moreover, the HCNS/MCS photocatalyst achieved a removal rate of 94% for tetracycline within 180 min under visible light, involving the center dot OH and center dot Oz radicals and following the proposed type-II mechanism. This work contributes to the design of highly efficient photocatalytic materials with synergistic effects for photocatalytic hydrogen evolution and organic pollutant degradation.

Developing dual functional catalysts for photocatalytic hydrogen evolution and pollutant degradation is one of the most ideal methods to address energy and environmental pollution. In the present study, an S-scheme ZnIn2S4/crystalline polymeric carbon nitride (ZIS/CPCN) heterojunction was synthesized using simple hydrothermal and calcination methods. The CPCN with a highly ordered heptazine-imide structure within the layer imparts a suitable band structure, while the widened interlayer spacing facilitates rapid electron transfer through surface engineering to construct heterojunctions. During the in-situ growth process, ZnIn2S4 uniformly distributes on the high surface area of CPCN as ultra-thin nanosheets. Under visible light irradiation, ZIS/CPCN-2 exhibited the highest hydrogen production activity (3492 mu mol center dot g(-1)center dot h(-1)), which was 4 times and 112 times higher than ZIS and CPCN, respectively. Furthermore, the ZIS/CPCN catalyst demonstrated a certain degradation rate for quinolone antibiotics within 180 min, involving the center dot OH and center dot O-2(-) radicals, and analyzed the degradation pathway of levofloxacin. The most stable configuration was obtained through theoretical calculations, and the density of states and work function of the sample were computed, proposing the S-scheme mechanism. This work contributes to the development of efficient photocatalytic systems with dual functions of hydrogen evolution and degradation.

Improving the stability and electron-hole separation efficiency of semiconductor photocatalysts has always been a hot topic in the field of catalysis. In the present study, a novel Cu2-xS@Mn0.3Cd0.7S (Cu2-xS@MCS) core-shell heterojunction has been constructed by the in-situ traditional hydrothermal reaction on the basis of hollow Cu2-xS nanocubes. The optimized Cu2-xS@MCS-2 photocatalyst with expanded light absorption exhibits excellent stability and a higher hydrogen evolution rate of 42.43 mmol g-1 h-1, which is 2.3 times and more than 1400 times contrasting to the pure Mn0.3Cd0.7S and Cu2-xS, respectively. Multiple characterizations and structure analysis revealed that the Cu2-xS@MCS heterojunction possesses outstanding charge separation efficiency and a wider specific surface area which can provide abundant active sites. Furthermore, the mechanism of photo-catalytic H2 evolution for Cu2-xS@Mn0.3Cd0.7S S-scheme heterojunction is also proposed. This work thus provides a favorable strategy to inhibit the photogenerated charge carrier recombination and drive highly efficient photocatalytic hydrogen generation by synthesizing photocatalyst with in situ core-shell structures.

The development of efficient catalysts for simultaneous photocatalytic hydrogen evolution and degradation of organic pollutants is one of the most ideal methods to solve energy problems and environmental pollution. In the present study, an S-scheme Mn0.25Cd0.75S/honeycomb-like g-C3N4 (MCS/HCN) heterojunction is synthesized using simple hydrothermal and calcination methods. It is found that the S-scheme MCS/HCN heterojunction can promote the separation and transfer of charge carriers through the IEF constructed after the rebalancing of Fermi energy levels. Under visible light irradiation, the degradation efficiency of amoxicillin (AMX) for the MCS/HCN composite is 98 %, and the synergistic production of hydrogen is 2668 mu mol center dot h(-1)center dot g(-1). The photocatalytic performance remains basically unchanged after four cycles. At the same time, the photodegradation path of AMX was analyzed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS). Furthermore, the photocatalytic H-2 evolution integrated with amoxicillin degradation mechanism of the S-scheme MCS/HCN heterojunction is also proposed. This work is helpful to design new photocatalyst materials with S-scheme heterojunction for simultaneous photocatalytic hydrogen evolution and degradation of organic pollutants.

The design and construction of low-cost and high-performance semiconductor is critical for the large-scale application of hydrogen energy. Hollow spherical carbon nitride (HCNS) is considered as a promising photocatalytic material due to its large inner space and appropriate band gap. Herein, 0D CdS QDs and 0D CoS nanoparticles are coated on HCNS to form a distinct double-shell structure by a facile in-situ preparation process. Based on the unique hierarchical structure, the photoinduced charge is spatially separated along the ternary catalysts to improve the electron transfer and reaction kinetics. The CoS/CdS@HCNS shows the highest H2 generation activity under visible light irradiation (2866 mu mol.g- 1.h- 1), which is 20.2 and 7.9 times higher than that of HCNS (142 mu mol.g- 1.h- 1) and CdS (363 mu mol.g- 1.h- 1), respectively. In addition, the 5%-CoS/ CdS@HCNS composite has high stability after 4 cycles of test. It provides a new strategy for exploring and manufacturing 0D/3D photocatalysts for energy and environmental applications.

3D CdMoO4@CdS core-shell visible-light-driven photocatalyst was successfully synthesized by in-situ method. Various analytical techniques show that CdS dots are uniformly loaded on the surface of CdMoO4 hollow microspheres constructing a 3D core-shell CdMoO4@CdS heterojunction. The photocatalytic activity of nano composites was studied by degrading malachite green (MG) under visible light irradiation. It was found that the composite material can effectively degrade MG under visible light irradiation. Furthermore, the enhanced photocatalytic efficiency for the composite material is due to the effective diffusion and separation of photo generated carriers.

CdS quantum dots (QDs) were decorated onto phosphorus-doped hexagonal g-C3N4 tube (P-CNT) to form a novel high-preformance photocatalyst (CdS QDs/P-CNT) via an in-situ oil bath approach. The ultra-small CdS QDs with the average diameter of similar to 9 nm are homogeneously anchored on the both external and internal surface of P-CNT hollow channel (similar to 25 mu m), yielding a type of zero-dimensional (0D)/one-dimensional (1D) heterojunction. The CdS QDs/P-CNT-1 exhibits the maximum photocatalytic H-2 evolution rate of 1579 mu mol h(-1) g(-1) under visible-light irradiation, which is 31.6, 6.8, 4.7 and 3.1 times higher than P-CNT, CdS, CdS/BCN and CdS/CNT, respectively. The improved photocatalytic activity of CdS QDs/P-CNT is primarily attributed to large surface area, P doping and formed 0D/1D heterojunction, which can broaden the light absorption, narrow the band gap, activate the H2O molecule and promote the spatial charge separation. Moreover, the DFT calculation coupled with experiment (Mott-Schottky curves) illustrates the electron transfer behavior of CdS QDs/P-CNT, showing that the Cd-1 site should be the main active center and P doping is beneficial to increase H-2 production. This work provides a new strategy to design of highly active 0D/1D photocatalyst for photocatalytic H-2 production. (C) 2020 Elsevier Inc. All rights reserved.

Honeycomb-like graphitic carbon nitride (H-C3N4) with unique morphology has been studied as a promising polymer photocatalyst. Herein, a novel binary metal sulfide constructed with H-C3N4 (Cd0.5Zn0.5S/H-C3N4) was prepared though the facile in situ precipitation method. The characterization data suggest that Cd0.5Zn0.5S quantum dots (QDs) are well dispersed on the macroporous structure of H-C3N4 (156 m(2) g(-1)), which can provide higher surface area, more catalytic active sites and larger interface contact area with accelerating the migration and separation of charge carriers. By taking advantage of 0D/3D heterojunction structure, the Cd0.5Zn0.5S/H-C3N4 dramatically boosts the photocatalytic H-2 evolution rate with the visible-light illumination. The Cd0.5Zn0.5S/H-C3N4-3 yields the highest photocatalytic activity of 5145 mu mol h(-1) g(-1), which is 4.3 times as high as that of pure Cd0.5Zn0.5S. Furthermore, Cd0.5Zn0.5S/H-C3N4 composite presents high stability after four recycles. The enhanced visible-light-driven photocatalytic H-2 production is attributed to the construction of n-n type heterojunction as well as the large surface area, which can inhibit the agglomeration of Cd0.5Zn0.5S nanoparticles, and efficiently transfer the photo excited electron-hole pairs in Cd0.5Zn0.5S. Therefore, this work provides a potential way for designing advanced 0D/3D heterojunction. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

In this study, LaFeO3/ZnIn2S4 composites were synthesized via in situ synthesis. The composition, structure and optical absorption properties of LaFeO3/ZnIn2S4 were characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy, fluorescence spectroscopy (PL), Fourier Transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The photocatalytic activity of the LaFeO3/ZnIn2S4 photocatalyst was determined based on the degradation of methyl orange (MO). LaFeO3/ZnIn2S4 composites showed much better photocatalytic performance compared with pure LaFeO3 and ZnIn2S4. The enhanced photocatalytic performance was attributed to intimately contacted interfaces and charge transfer channels which can effectively transfer and separate the photogenerated charge carriers.