In situ preparation of g-C3N4 nanosheet/FeOCl: Achievement and promoted photocatalytic nitrogen fixation activity

Decade Milestone Advancement of Defect-Engineered g-C3N4 for Solar Catalytic Applications

Over the past decade, graphitic carbon nitride (g-C3N4) has emerged as a universal photocatalyst toward various sustainable carbo-neutral technologies. Despite solar applications discrepancy, g-C3N4 is still confronted with a general fatal issue of insufficient supply of thermodynamically active photocarriers due to its inferior solar harvesting ability and sluggish charge transfer dynamics. Fortunately, this could be significantly alleviated by the "all-in-one" defect engineering strategy, which enables a simultaneous amelioration of both textural uniqueness and intrinsic electronic band structures. To this end, we have summarized an unprecedently comprehensive discussion on defect controls including the vacancy/non-metallic dopant creation with optimized electronic band structure and electronic density, metallic doping with ultra-active coordinated environment (M-Nx, M-C2N2, M-O bonding), functional group grafting with optimized band structure, and promoted crystallinity with extended conjugation π system with weakened interlayered van der Waals interaction. Among them, the defect states induced by various defect types such as N vacancy, P/S/halogen dopants, and cyano group in boosting solar harvesting and accelerating photocarrier transfer have also been emphasized. More importantly, the shallow defect traps identified by femtosecond transient absorption spectra (fs-TAS) have also been highlighted. It is believed that this review would pave the way for future readers with a unique insight into a more precise defective g-C3N4 "customization", motivating more profound thinking and flourishing research outputs on g-C3N4-based photocatalysis.

Research Progress in Composite Materials for Photocatalytic Nitrogen Fixation

Ammonia is an essential component of modern chemical products and the building unit of natural life molecules. The Haber-Bosch (H-B) process is mainly used in the ammonia synthesis process in the industry. In this process, nitrogen and hydrogen react to produce ammonia with metal catalysts under high temperatures and pressure. However, the H-B process consumes a lot of energy and simultaneously emits greenhouse gases. In the "double carbon" effect, to promote the combination of photocatalytic technology and artificial nitrogen fixation, the development of green synthetic reactions has been widely discussed. Using an inexhaustible supply of sunlight as a power source, researchers have used photocatalysts to reduce nitrogen to ammonia, which is energy-dense and easy to store and transport. This process completes the conversion from light energy to chemical energy. At the same time, it achieves zero carbon emissions, reducing energy consumption and environmental pollution in industrial ammonia synthesis from the source. The application of photocatalytic technology in the nitrogen cycle has become one of the research hotspots in the new energy field. This article provides a classification of and an introduction to nitrogen-fixing photocatalysts reported in recent years and prospects the future development trends in this field.

In Situ Fabrication of an S-Scheme NaNbO3/Bi2O2CO3 Heterojunction for Enhanced Performance in Photocatalytic Nitrogen Fixation

In this study, NaNbO3 microcubes were introduced during the preparation of Bi2O2CO3 nanosheets to construct a series of NaNbO3/Bi2O2CO3 heterojunctions with varying NaNbO3 content. Their photoactivities for N2 fixation were examined and compared. Results demonstrated that 7.5% NaNbO3/Bi2O2CO3 had the highest photoactivity. The NH3 production rate under simulated solar light is 453.1 μmol L-1 g-1 h-1, representing 2.0 and 3.8-fold increases compared to those of Bi2O2CO3 and NaNbO3, respectively. A comprehensive investigation encompassing the physical and chemical properties of the NaNbO3/Bi2O2CO3 photocatalyst was conducted. Bi2O2CO3 nanosheets were discovered to be distributed on the NaNbO3 microcubes surface. The addition of NaNbO3 exhibited nearly no effect on the photoabsorption performance and specific surface area of the Bi2O2CO3. However, the tight contact between NaNbO3 and Bi2O2CO3 and their appropriate band positions led to the formation of a heterojunction structure between them. The electron drift occurring in the interface region induces the creation of an internal electric field and energy band bending. This facilitates the transfer of photogenerated electrons and holes through an S-scheme mechanism, achieving efficient separation without compromising the redox performance. As a result, the NaNbO3/Bi2O2CO3 composite exhibits exceptional performance in the photocatalytic nitrogen fixation reaction. This study expands the application of S-scheme photocatalysts in the field of N2 reduction and provides insights into the preparation of efficient S-scheme photocatalysts.

Promoted wet peroxide oxidation of chlorinated volatile organic compounds catalyzed by FeOCl supported on macro-microporous biomass-derived activated carbon

Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H₂O₂ to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO^• to be the dominant ROS in the FeOCl/BAC + H₂O₂ system. The wet scrubber performs well at pH 3 and H₂O₂ concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H₂O₂ to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants.

A novel scheme to improve the photo-Fenton performance of iron oxychloride by carbon: Three existent states and roles of carbon in the degradation of tetracycline in water

The photo-Fenton process is promising for sincerely treating contaminated water. In this work, carbon-decorated iron oxychloride (C-FeOCl) is synthesized as a photo-Fenton catalyst for removing tetracycline (TC) from water. Three actual states of carbon are identified and their different roles in enhancing photo-Fenton performance are revealed. All carbon on/in FeOCl, including graphite carbon, carbon dots and lattice carbon, enhance visible light adsorption. More importantly, a homogeneous graphite carbon on the outer surface of FeOCl accelerates the transportation-separation of photo-excited electrons along the horizontal direction of FeOCl. Meanwhile, the interlayered carbon dots offer a FeOC bridge in helping the transportation-separation of photo-excited electrons along the vertical direction of FeOCl. In this way, C-FeOCl acquires isotropy in conduction electrons to ensure an efficient Fe(II)/Fe(III) cycle. These interlayered carbon dots extend the layer spacing (d) of FeOCl to about 1.10 nm, exposing the internal iron centers. The lattice carbon significantly increases the amounts of coordinatively unsaturated iron sites (CUISs) in activating hydrogen peroxide (H₂O₂) to hydroxyl radical (OH). Density functional theory (DFT) calculations confirm this activation on inner and external CUISs with a significantly low activation energy of about 0.33 eV.

Recent Advances in g-C3N4-Based Photocatalysts for NOx Removal

Nitrogen oxides (NOx) pollutants can cause a series of environmental issues, such as acid rain, ground-level ozone pollution, photochemical smog and global warming. Photocatalysis is supposed to be a promising technology to solve NOx pollution. Graphitic carbon nitride (g-C3N4) as a metal-free photocatalyst has attracted much attention since 2009. However, the pristine g-C3N4 suffers from poor response to visible light, rapid charge carrier recombination, small specific surface areas and few active sites, which results in deficient solar light efficiency and unsatisfactory photocatalytic performance. In this review, we summarize and highlight the recent advances in g-C3N4-based photocatalysts for photocatalytic NOx removal. Firstly, we attempt to elucidate the mechanism of the photocatalytic NOx removal process and introduce the metal-free g-C3N4 photocatalyst. Then, different kinds of modification strategies to enhance the photocatalytic NOx removal performance of g-C3N4-based photocatalysts are summarized and discussed in detail. Finally, we propose the significant challenges and future research topics on g-C3N4-based photocatalysts for photocatalytic NOx removal, which should be further investigated and resolved in this interesting research field.

Adsorption-enforced Fenton-like process using activated carbon-supported iron oxychloride catalyst for wet scrubbing of airborne dichloroethane

Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H₂O₂ and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H₂O₂ concentrations. By pulsed or continuous dosing H₂O₂, the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control.

Recent Advances in Application of Graphitic Carbon Nitride-Based Catalysts for Photocatalytic Nitrogen Fixation

Ammonia, the second most-produced chemical, is widely used in agricultural and industrial applications. However, traditional industrial ammonia production dominated by the Haber-Bosch process presents huge resource and environment issues due to the massive energy consumption and CO₂ emission. The newly emerged nitrogen fixation technology, photocatalytic N₂ reduction reaction (p-NRR), uses clean solar energy with zero-emission, holding great prospect to achieve sustainable ammonia synthesis. Although great efforts are made, the p-NRR catalysts still suffer from poor N₂ adsorption and activation, inferior light absorption, and fast recombination of photocarriers. Due to the tunable electronic structure of the metal-free polymeric graphitic carbon nitride (g-C₃ N₄ ), the above-mentioned issues can be significantly alleviated, making it the most promising p-NRR photocatalyst. This review summarizes the recent development of g-C₃ N₄ -based catalysts for p-NRR, including the working principle of p-NRR catalysts, the challenges of developing p-NRR catalysts, and corresponding solutions. Particularly, the roles of defect engineering and heterojunction construction on g-C₃ N₄ to the enhancement of photocatalytic performances are emphasized. In addition, computational studies are introduced to deepen the understanding of reaction pathways. At last, perspectives are provided on the development of p-NRR catalysts.

Synthesis, Performance Measurement of Bi2SmSbO7/ZnBiYO4 Heterojunction Photocatalyst and Photocatalytic Degradation of Direct Orange within Dye Wastewater under Visible Light Irradiation

Originally, the new catalyst Bi2SmSbO7 was synthesized by the hydrothermal synthesis method or by the solid-phase sintering method at a lofty temperature. A solvothermal method was utilized to prepare a Bi2SmSbO7/ZnBiYO4 heterojunction photocatalyst (BZHP). The crystal structure of Bi2SmSbO7 belonged to the pyrochlore structure and face-centered cubic crystal system by the space group of Fd3m. The cell parameter a was equivalent to 10.835(1) Å (Bi2SmSbO7). With Bi2SmSbO7/ZnBiYO4 heterojunction (BZH) as the photocatalyst, the removal rate (RR) of direct orange (DO) and the total organic carbon were 99.10% and 96.21% after visible light irradiation of 160 min (VLI-160M). The kinetic constant k toward DO concentration and visible light irradiation time (VLI) with BZH as photocatalyst reached 2.167 min−1. The kinetic constant k, which was concerned with total organic carbon, reached 0.047 min−1. The kinetic curve that came from DO degradation with BZH as a catalyst under VLI conformed to the second-order reaction kinetics. After VLI-160M, the photocatalytic degradation (PD) removal percentage of DO with BZH as the photocatalyst was 1.200 times, 1.268 times or 3.019 times that with Bi2SmSbO7 as the photocatalyst, ZnBiYO4 as the photocatalyst or with nitrogen-doped titanium dioxide as the photocatalyst. The photocatalytic activity (PA) was as following: BZH > Bi2SmSbO7 > ZnBiYO4 > nitrogen-doped titanium dioxide. After VLI-160M for three cycles of experiments with BZH as the photocatalyst, the RR of DO reached 98.03%, 96.73% and 95.43%, respectively, which meant that BZHP possessed high stability. By using the experiment of adding a trapping agent, the oxidative purifying capability for degradation of direct orange, which was in gradual depressed order, was as following: hydroxyl radical > superoxide anion > holes. Finally, the possible degradation pathway and degradation mechanism of DO were discussed systematically. A new high active heterojunction catalyst BZHP, which could efficiently remove toxic organic pollutants such as DO from dye wastewater after VLI, was obtained. Our research was meant to improve the photocatalytic property of the single photocatalyst.

Preparation of Cu modified g-C3N4 nanorod bundles for efficiently photocatalytic CO2 reduction

Carbon nitride-based photocatalysts for CO₂ reduction have received great attention. The introduction of transition metals can effectively improve the photocatalytic efficiency of carbon nitride. However, how to introduce transition metals into carbon nitride in more ways remains a challenge. Herein, the Cu modified g-C₃N₄ nanorod bundles (CCNBs) were prepared by chemical vapor co-deposition using the mixture of urea and chlorophyllin sodium copper salt as precursor. The prepared CCNBs exhibited excellent photocatalytic activity for CO₂ reduction. The unique hierarchical structure was beneficial to enhance light harvesting. Besides, the introduction of uniformly dispersed Cu further improved the absorption capacity of visible light, increased active sites, and promoted the separation and transfer of carriers. The CO yield of CCNBs was 5 times higher than that of bulk g-C₃N₄, and showed excellent stability in cycle experiments. This work provides a strategy to prepare carbon nitride-based photocatalysts for efficient CO₂ reduction.

New and highly efficient Ultra-thin g-C3N4/FeOCl nanocomposites as photo-Fenton catalysts for pollutants degradation and antibacterial effect under visible light

The photo-Fenton reaction was widely used in the removal of pollutants in waste water, which makes it exhibit great potential in the field of environmental remediation. Hence, it is crucial to explore a new efficient and stable photo-Fenton catalyst driven by visible light. In this work, a simple two-step calcination method was used to synthesize sheet-like stacked Ultra-thin g-C₃N₄/FeOCl (CNF) materials. The morphology, composition, photo-Fenton performance, and antibacterial properties were systematically analyzed. Research results exhibited that the synthesized CNF catalysts showed enhanced visible light absorption capacity and excellent photo-Fenton performance. Compared with FeOCl alone, CNF displayed stronger degradation ability for rhodamine B (RhB) and could achieve 97% degradation within 9 min, which was about 10 times that of pure FeOCl. At the same time, the composite catalysts exhibited excellent antibacterial effects under photo-Fenton conditions. The antibacterial rate of CNF composite catalyst under photo-Fenton conditions can reach almost 99%, which was 3 times that of photocatalysis alone and 2 times that of Fenton alone. The heterojunction formed between Ultra-thin g-C₃N₄ and FeOCl promoted the separation of e^- and h⁺. Simultaneously, the presence of e^- promoted the cycle of Fe³⁺ and Fe²⁺ in FeOCl, thereby promoting the generation of hydroxyl radicals (OH) from H₂O₂ and improving the photo-Fenton activity to achieve the effect of degrading pollutants and antibacterial. The photo-Fenton catalysis and degradation mechanism were analyzed in detail. This work provided a theoretical basis for the application of CNF material in the removal of wastewater.

The fabrication of graphitic carbon nitride hollow nanocages with semi-metal 1T' phase molybdenum disulfide as co-catalysts for excellent photocatalytic nitrogen fixation

Improving the efficiency of photogenerated carrier separation is essential for photocatalytic N₂ fixation. Herein, the 2D semi-metal 1T'-MoS₂ was uniformly distributed in g-C₃N₄ nanocages (CNNCs) by a hydrothermal method, and the 1T'-MoS₂/CNNC composite was obtained. 1T'-MoS₂ as a co-catalyst can promote the transfer of electrons, improve the separation efficiency of photogenerated carriers, and also increase the number of effective active sites. In addition, the unique nanocage morphology of CNNCs is conducive to the scattering and reflection of incident light and improves the light absorption capacity. Therefore, the optimized 1T'-MoS₂/CNNC composite (5 wt%) shows a significantly improved photocatalytic N₂ fixation rate (9.8 mmol L^-1 h^-1 g^-1) and good stability, which is significantly higher than pure CNNCs (2.9 mmol L^-1 h^-1 g^-1), Pt/CNNC (8.2 mmol L^-1 h^-1 g^-1) and Pt/g-C₃N₄ nanosheet (CNNS, 6.3 mmol L^-1 h^-1 g^-1). This work guides guidance for the design of green and efficient N₂ fixation photocatalysts.

New FeOCl/graphene quantum dots catalyst for peroxymonosulfate activation to efficiently remove organic pollutants and inactivate Escherichia coli

The sulfate radical-based advanced oxidation processes (SR-AOPs) are well-established and efficient techniques for degradation of organic pollutants. Fe2+ is used as an environmentally friendly and cost-effective catalyst for activating peroxymonosulfate...

N-doping TiO2 hollow microspheres with abundant oxygen vacancies for highly photocatalytic nitrogen fixation

Photocatalytic fixation of nitrogen to ammonia (NH₃) is a green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N₂ and the band position of TiO₂ are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO₂ hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol g_cat^-1h^-1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H₂O₂ treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol g_cat^-1h^-1 after reducing oxygen vacancies by H₂O₂ treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol g_cat^-1h^-1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.

Self-Assembly of a 3D Hollow BiOBr@Bi-MOF Heterostructure with Enhanced Photocatalytic Degradation of Dyes

Considering the flexibility, adjustable pore structure, and abundant active sites of metal-organic frameworks (MOFs), rational design and fine control of the MOF-based hetero-nanocrystals is a highly important and challenging subject. In this work, self-assembly of a 3D hollow BiOBr@Bi-MOF microsphere was fabricated through precisely controlled dissociation kinetics of the self-sacrificial template (BiOBr) for the first time, where the residual quantity of BiOBr and the formation of Bi-MOF were carefully regulated by changing the reaction time and the capability of coordination. Meanwhile, the hollow microstructure was formed in BiOBr@Bi-MOF through the Oswald ripening mechanism to separate photogenerated electron-hole pairs and increase the adsorption capacity of Bi-MOF for dyes, which significantly enhanced the photocatalytic degradation efficiency of RhB from 56.4% for BiOBr to 99.4% for the optimal BiOBr@Bi-MOF microsphere. This research broadens the selectivity of semiconductor/MOF hetero-nanocrystals with reasonable design and flexible synthesis.

Heterojunction-based photocatalytic nitrogen fixation: principles and current progress

Nitrogen fixation is considered one of the grand challenges of the 21st century for achieving the ultimate vision of a green and sustainable future. It is crucial to develop and design sustainable nitrogen fixation techniques with minimal environmental impact as an alternative to the energy-cost intensive Haber-Bosch process. Heterojunction-based photocatalysis has recently emerged as a viable solution for the various environmental and energy issues, including nitrogen fixation. The primary advantages of heterojunction photocatalysts are spatially separated photogenerated charge carriers while retaining high oxidation and reduction potentials of the individual components, enabling visible light-harvesting. This review summarises the fundamental principles of photocatalytic heterostructures, the reaction mechanism of the nitrogen reduction reaction, ammonia detection methods, and the current progress of heterostructured photocatalysts for nitrogen fixation. Finally, future challenges and prospects are briefly discussed for the emerging field of heterostructured photocatalytic nitrogen fixation.

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst

The interesting g-C3N4 nanosheet morphology has drawn huge attention in photocatalytic applications because of its special features. Nonetheless, the relative activity of these nanosheets is still controversial due to the low available active sites and the high recombination probability of photo-induced charge carriers. In this work, in situ sol-gel approach was applied to synthesize holey g-C3N4 nanosheets/hydroxyapatite (HAp) nanospheres with plentiful in-plane holes. Herein, the presence of Ca2+ plays a key role in the formation of holey defects on 2D g-C3N4. In-plane holes provide nanosheets with more active edges and diffusion channelsv, resulting in a tremendous enhanced mass and photo-induced charge transfer speed. Moreover, the holes make highly numbered boundaries, which lead to the prevention of aggregation. On the other hand, distributed nano-HAp spheres on these nanosheets can form effective heterojunctions having high photo-degradation ability of pollutants. Intrinsic O-vacancies inside HAp unit cells mainly affect the capture of photogenerated electrons, pollutant molecules, and O2 gas. The synergistic presence of O-vacancies and holey defects (C-vacancies) on 2D g-C3N4 plays a key role in raising the photocatalytic performance of holey g-C3N4/HAp. It can be concluded that the proposed preparation method is a promising approach for simultaneous synthesis of holey g-C3N4 and surface heterojunctions of Ca-based materials. This new structure has shown significant degradation ability of bisphenol A, a prominent pollutant, with a low amount (0.01 g) and short time.

Construction 0D/2D heterojunction by highly dispersed Ag2S quantum dots (QDs) loaded on the g-C3N4 nanosheets for photocatalytic hydrogen evolution

In recent years, the use of quantum dots (QDs) cocatalysts to improve the hydrogen evolution activity from the water splitting of photocatalysts has become a popular research topic. Herein, we successfully prepared a novel 0 dimension/2 dimension (0D/2D) heterojunction nanocomposite (denoted Ag₂S quantum dots (QDs)/g-C₃N₄) with excellent photocatalytic performance by anchoring the Ag₂S QDs cocatalyst on the surface of g-C₃N₄ through a self-assembly strategy. Ag₂S QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-C₃N₄. The Ag₂S QDs/g-C₃N₄ composite with 0.5 wt% Ag₂S QDs loading achieved the highest hydrogen evolution rate of 471.1 μmol·g^-1·h^-1 with an apparent quantum efficiency (AQE) of 1.48% at 405 nm. Such remarkable hydrogen evolution activity far exceeded that of undoped g-C₃N₄ and Ag₂S nanoparticles (NPs)/g-C₃N₄. Moreover, it was 2.04 times the activity of Pt/g-C₃N₄ with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of Ag₂S QDs caused by the quantum size effect and the convenient and effective charge transfer between g-C₃N₄ and Ag₂S QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H₂ evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.

New g-C3N4/GO/MoS2 composites as efficient photocatalyst for photocathodic protection of 304 stainless steel

Photocathodic protection is an economical and environmental metal anticorrosion method. In this research, we successfully synthesized the g-C₃N₄/GO (15 wt%)/MoS₂ catalytic materials by a facile hydrothermal method. The results show that the as-prepared g-C₃N₄/GO (15 wt%)/MoS₂ composites prominently enhanced photocatalytic activities for the photocathodic protection of 304 stainless steel (SS) compared with the corresponding pristine g-C₃N₄ and MoS₂. Notably, the AC impedance results demonstrated that the Rct value of 304 SS coupled with g-C₃N₄/GO (15 wt%)/MoS₂ decreased to 35.66 Ω•cm², which is 29 and 37 times lower than that of g-C₃N₄ and MoS₂ alone. In addition, g-C₃N₄/GO (15 wt%)/MoS₂ provided the highest current density (77.19 μA•cm²) for the 304 SS, which is four times that of pristine g-C₃N₄. All results indicate that as-prepared g-C₃N₄/GO (15 wt%)/MoS₂ photocatalysts have produced a distinct enhancement on photocathodic protection performance. An optimum decorating amount of MoS₂ onto g-C₃N₄ forms heterojunctions of g-C₃N₄/MoS₂, which favor the separation of electrons and holes efficiently. Furthermore, the addition of GO further promotes the separation and transfer of photo-induced carriers.

3D hollow Bi2O3@CoAl-LDHs direct Z-scheme heterostructure for visible-light-driven photocatalytic ammonia synthesis

In this paper, the novel 3D hollow Z-scheme heterojunction photocatalysts based on Bi₂O₃ and CoAl layered double hydroxides (Bi₂O₃@CoAl-LDHs) were prepared for efficient visible-light-driven photocatalytic ammonia synthesis. The synthesized nanohybrid exhibits excellent photocatalytic ammonia synthesis performance (48.7 μmol·L^-1·h^-1) and structural stability, which is primarily attributed to the fact that Z-scheme heterojunction significantly enhanced lifetime of photogenerated carriers (6.22 ns) and transfer efficiency of surface photogenerated electrons (72.5%). Strict control experiments and nitrogen isotope labeling results show that nitrogen and hydrogen in the produced ammonia come from nitrogen and water in the reactant respectively. Electron paramagnetic resonance (EPR) experiments and density functional theory (DFT) calculations further reveal that the built-in electric field due to the difference between Bi₂O₃ and CoAl-LDHs is the key to constructing the Z-scheme heterojunction. In addition, results of partial density of states (PDOS) show that Co in Bi₂O₃@CoAl-LDHs composite is the active site for photocatalytic N₂ fixation.

g-C3N4 Sensitized by an Indoline Dye for Photocatalytic H2 Evolution

Protonated g-C3N4 (pCN) formed by treating bulk g-C3N4 with an aqueous HCl solution was modified with D149 dye, i.e., 5-[[4[4-(2,2-diphenylethenyl) phenyl]-1,2,3,3a,4,8b-hexahydrocyclopent[b]indol-7-yl] methylene]-2-(3-ethyl-4-oxo-2-thioxo-5-thiazolidinylidene)-4-oxo-thiazolidin-2-ylidenerhodanine, for photocatalytic water splitting (using Pt as a co-catalyst). The D149/pCN-Pt composite showed a much higher rate (2138.2 µmol·h−1·g−1) of H2 production than pCN-Pt (657.0 µmol·h−1·g−1). Through relevant characterization, the significantly high activity of D149/pCN-Pt was linked to improved absorption of visible light, accelerated electron transfer, and more efficient separation of charge carriers. The presence of both D149 and Pt was found to be important for these factors. A mechanism was proposed.

Constructing electron transfer pathways and active centers over W18O49 nanowires by doping Fe3+ and incorporating g-C3N5 for enhanced photocatalytic nitrogen fixation

A compound constructed from fluffy and porous g-C₃N₅ with OV-rich Fe-W₁₈O₄₉ was employed in the photocatalytic nitrogen fixation. The formation rate of ammonia reached 131.6 μmol g⁻¹ h⁻¹ when Fe-W₁₈O₄₉/g-C₃N₅ was employed as the catalyst.