Nitrogen-rich carbon nitride (C3N5) coupled with oxygen vacancy TiO2 arrays for efficient photocatalytic H2O2 production

TiO2 Supporting Cu-Au Alloy Nanoparticles for Photocatalytic Methanol Reforming to Hydrogen Production

Methanol steam reforming (MSR) is a promising approach for hydrogen production, allowing for efficient production and safe transportation of hydrogen via liquid methanol. However, it requires relatively high temperatures to achieve high activity, resulting in huge energy consumption. In this study, a plasma copper-gold alloy catalyst supported on titanium dioxide was synthesized via the impregnation method followed by high-temperature calcination. The resulting nanoparticles exhibited an average size of approximately 12 nm, and their composition was controlled by adjusting the molar ratio of the precursor materials. The synthesized CuAu-TiO2 catalyst facilitates efficient solar-driven MSR without the need for additional thermal input. The optimized catalyst achieves a continuous hydrogen production rate of 78 µmol·g-1·h-1, with a solar energy conversion efficiency of 2.66%. We determined that the maximum conversion rate under photochemical catalysis conditions can reach 90.6%. We verified that the plasmon-induced hot carriers could catalyze the methanol steam reforming reaction at temperatures significantly lower than those required for traditional thermal catalysis, releasing hydrogen. Post-reaction, the catalyst can be recovered and reactivated for repeated use. This work provides a valuable demonstration for the development and application of future light-driven clean energy conversion systems.

Hollow flower-like WO3@TiO2 heterojunction microspheres for the photocatalytic degradation of rhodamine B and tetracycline

In the context of sustainable development, the utilization of semiconductor materials for the degradation of dyes, antibiotics, heavy metals, and pesticides in wastewater under visible light has emerged as a focal point of contemporary research. In this investigation, a WO3@TiO2 composite was synthesized via a solvothermal method, with the composite exhibiting a molar ratio of 5% WO3 to TiO2 precursors demonstrating optimal photocatalytic degradation performance. This material achieved complete degradation of 20 mg per L Rhodamine B (RhB) dye and tetracycline (TC) antibiotic within 30 min. Furthermore, the effects of initial pollutant concentration and solution pH on catalytic efficacy were systematically explored. The findings revealed that at RhB concentrations below 40 mg L-1, the degradation proceeded at an accelerated rate, with a rate constant exceeding 0.128 min-1. The catalyst exhibited robust performance across a broad pH range, attaining peak degradation efficiency at pH ≈ 3. The exceptional photocatalytic prowess of the WO3@TiO2 composite is predominantly attributable to its distinctive hollow microstructure, the intimate interfacial synergy between WO3 and TiO2, and the efficient separation of photogenerated electrons and holes facilitated by the type-II heterojunction architecture.

Improved H2O2 Photogeneration on KBr Doped-Polymeric Carbon Nitride Via Optimize the Oxygen Reduction Path

The photosynthesis of hydrogen peroxide (H2O2) from oxygen (O2) represents a promising catalytic pathway, the limited efficiency of the oxygen reduction constitutes a primary barrier to enhancing production. In this content, alkali metal potassium (K+) and Br-doped g-C3N4 photocatalysts (K-CN) were successfully constructed by one-pot method. The introduction of K+ is not only beneficial to the transmission of space charge and the separation efficiency of photogenerated carriers, but also promotes the efficient production of H2O2 by 2e- oxygen reduction reaction. The introduction of Br- promotes O2 converted to triplet state and triggers energy transfer process to increase 1O2 production, O2 adsorption was facilitated through regulating the oxygen evolution (O2→1O2), which is beneficial to the subsequent oxygen reduction process. The results showed that the H2O2 yield of 0.05 K-CN catalyst reached 26.0 mmol g-1 h-1, which was more than 5 times that of pure g-C3N4.

Mechanism, Performance, and Application of g-C3N5-Coupled TiO2 as an S-Scheme Heterojunction Photocatalyst for the Abatement of Gaseous Benzene

In this research, S-scheme heterojunction photocatalysts are prepared through the hybridization of nitrogen-rich g-C3N5 with TiO2 (coded as TCN5-(x): x as the weight ratio of TiO2:g-C3N5). The photocatalytic potential of TCN5-(x) is evaluated against benzene (1-5 ppm) across varying humidity levels using a dynamic flow packed-bed photocatalytic reactor. Among the prepared composites, TCN5-(10) exhibits the highest synergy between g-C3N5 and TiO2 at "x" ratio of 10%, showing superior best benzene degradation performance (e.g., 93.9% removal efficiency, specific clean air delivery rate of 1126.9 L g-1 h-1, kinetic reaction rate of 46.1 nmol mg-1 min-1, quantum yield of 6.0 × 10-4 molec. photon-1, and space-time yield of 1.2 × 10-4 molec. photon-1 mg-1). The formation of an S-scheme heterojunction with a built-in internal electric field is supported by both theoretical (through the density functional theory calculations) and photoelectrochemical bases (e.g., improvement in the band potential and electrochemistry along with surface characteristics (e.g., reactive sites and charge migrations at the interface)). The results of the in situ DRIFTS analysis confirm that the oxidation of benzene molecules is accompanied by many reaction intermediates (e.g., phenolate, maleate, acetate, and methylene). The outcomes of this work will help us pursue the development of a state-of-the-art photocatalytic system for air quality management.

Highly efficient photoenzymatic CO2 reduction dominated by 2D/2D MXene/C3N5 heterostructured artificial photosynthesis platform

Photoenzyme-coupled catalytic systems offer a promising avenue for selectively converting CO2 into high-value chemicals or fuels. However, two key challenges currently hinder their widespread application: the heavy reliance on the costly coenzyme NADH, and the necessity for metal-electron mediators or photosensitizers to address sluggish reaction kinetics. Herein, we present a robust 2D/2D MXene/C3N5 heterostructured artificial photosynthesis platform for in situ NADH regeneration and photoenzyme synergistic CO2 conversion to HCOOH. The efficiencies of utilizing and transmitting photogenerated charges are significantly enhanced by the abundant π-π conjugation electrons and well-engineered 2D/2D hetero-interfaces. Noteworthy is the achievement of nearly 100 % NADH regeneration efficiency within just 2.5 h by 5 % Ti3C2/C3N5 without electron mediators, and an impressive HCOOH production rate of 3.51 mmol g-1h-1 with nearly 100 % selectivity. This study represents a significant advancement in attaining the highest NADH yield without electron mediator and provides valuable insights into the development of superior 2D/2D heterojunctions for CO2 conversion.

Structurally and surficially activated TiO2 nanomaterials for photochemical reactions

Renewable fuels and environmental remediation are of paramount importance in today's world due to escalating concerns about climate change, pollution, and the finite nature of fossil fuels. Transitioning to sustainable energy sources and addressing environmental pollution has become an urgent necessity. Photocatalysis, particularly harnessing solar energy to drive chemical reactions for environmental remediation and clean fuel production, holds significant promise among emerging technologies. As a benchmark semiconductor in photocatalysis, TiO2 photocatalyst offers an excellent solution for environmental remediation and serves as a key tool in energy conversion and chemical synthesis. Despite its status as the default photocatalyst, TiO2 suffers from drawbacks such as a high recombination rate of charge carriers, low electrical conductivity, and limited absorption in the visible light spectrum. This review provides an in-depth exploration of the fundamental principles of photocatalytic reactions and presents recent advancements in the development of TiO2 photocatalysts. It specifically focuses on strategic approaches aimed at enhancing the performance of TiO2 photocatalysts, including improving visible light absorption for efficient solar energy harvesting, enhancing charge separation and transportation efficiency, and ensuring stability for robust photocatalysis. Additionally, the review delves into the application of photodegradation and photocatalysis, particularly in critical processes such as water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide generation, and alcohol oxidation. It also highlights the novel use of TiO2 in plastic polymerization and degradation, showcasing its potential for converting plastic waste into valuable chemicals and fuels, thereby offering sustainable waste management solutions. By addressing these essential areas, the review offers valuable insights into the potential of TiO2 photocatalysis for addressing pressing environmental and energy challenges. Furthermore, the review encompasses the application of TiO2 photochromic systems, expanding its scope to include other innovative research and applications. Finally, it addresses the underlying challenges and provides perspectives on the future development of TiO2 photocatalysts. Through addressing these issues and implementing innovative strategies, TiO2 photocatalysis can continue to evolve and play a pivotal role in sustainable energy and environmental applications.

Introducing Br, K, and cyano group into carbon nitride for efficient photocatalytic hydrogen peroxide production then in situ tetracycline mineralization

In this work, Br, K-doped and cyano group-rich carbon nitride (CN) were prepared via pyrolysis of molten urea and 6-Bromopyridine-3-carbaldehyde, followed by re-calcination with potassium thiocyanate. The hydrogen peroxide (H2O2) evolution and in situ tetracycline (TC) mineralization performances of the prepared samples were studied. The optimal sample could produce 9127 μmol g-1 h-1 H2O2 from 10 vol% ethanol solution and air atmosphere, which was 10.9 times higher than that of pristine CN. With addition of 4 mg L-1 Fe2+ ions, 97.2% of TC (10 mg L-1) and 98.7% of total organic carbon were removed in 30 min under the actions of holes, hydroxyl and superoxide radicals. The high H2O2 yield and TC mineralization ratio were attributed to the increased light absorption, efficient electrons-holes separation, enhanced surface O2 adsorption (0.3878 mmol g-1), and accelerated conversion from Fe3+ to Fe2+ ions. Meanwhile, the system possessed good reusability in H2O2 evolution and TC removal. It is expected that this work can provide new ideas to design CN-based photo-Fenton system to treat wastewater.

Construction of a BiOCl/Bi2O2CO3 S-Scheme Heterojunction Photocatalyst via Sharing [Bi2O2]2+ Slabs with Enhanced Photocatalytic H2O2 Production Performance

The construction of a close contact interface is key to enhancing the photocatalytic activity in heterojunctions. In the work, the BiOCl/Bi2O2CO3 of sharing [Bi2O2]2+ slabs S-scheme heterojunction was prepared by a HCl in situ etching method. The optimal composite photocatalyst could accomplish sizable productivity of H2O2 to 2562.95 μmol g-1 h-1 under simulated solar irradiation, higher than that of primitive Bi2O2CO3 and BiOCl. Moreover, the synthesized catalysts showed good stability. The band structures of BiOCl and Bi2O2CO3 were determined, confirming the formation of BiOCl/Bi2O2CO3 S-scheme heterojunction The BiOCl/Bi2O2CO3, which obviously improved the separation efficiency of photoinduced carriers and effectively enhanced the redox ability of the photocatalyst. In addition, density functional theory (DFT) calculations were utilized to analyze the electron transfer properties and the constitution of the built-in electric field at the interface of BiOCl and Bi2O2CO3. The photocatalytic reaction process was further researched by electron paramagnetic resonance (EPR), indicating the active species in the photocatalytic production of hydrogen peroxide. Eventually, a feasible S-scheme electron transfer mechanism on the BiOCl/Bi2O2CO3 heterojunction during the photocatalytic H2O2 production process was proposed and discussed. This work provides a reliable strategy for the fine design of the S-scheme heterojunction.

Mediating peroxymonosulfate activation path in Fenton-like reaction via doping different metal atoms into g-C3N5

Peroxymonosulfate (PMS) could be activated by either radical path or non-radical path, how to rationally mediate these two routines was an important unresolved issue. This work has introduced a simple way to address this problem via metal atom doping. It was found that Fe-doped nitrogen-rich graphitic carbon nitride (Fe-C3N5) exhibited high activity towards PMS activation for tetracycline degradation, and the degradation rate was 3.14 times higher than that of Co-doped nitrogen-rich graphitic carbon nitride (Co-C3N5). Radical trapping experiment revealed the contributions of reactive species over two catalysts were different. Electron paramagnetic resonance analysis further uncovered the non-radical activation path played a dominated role on Fe-C3N5 surface, while the radical activation path was the main routine on Co-C3N5 surface. Density functional theory calculations, X-ray photoelectron spectroscopy analysis, and electrochemical experiments provided convincing evidence to support these views. This study supplied a novel method to mediate PMS activation path via changing the doped metal atom in g-C3N5 skeleton, and it allowed us to better optimize the PMS activation efficiency.

An innovative Z-type Sb2S3/In2S3/TiO2 heterostructure: superior performance in the photocatalytic removal of levofloxacin and mechanistic insight

In this study, Sb2S3/In2S3/TiO2 (SIT) heterojunction photocatalysts were prepared by a simple two-step hydrothermal method and applied to the photocatalytic degradation of levofloxacin (LEV). After 160 min of reaction under visible light, the SIT heterojunction photocatalyst degraded 10 mg L-1 LEV at a rate of 86.7%. The degradation of LEV follows pseudo-first-order kinetics with a rate constant 1.16 × 10-2 min-1, which is 1.42, 1.22 and 1.05 times higher than that of TiO2, SI and IT, respectively. Meanwhile, the SIT photocatalysts also showed high photocatalytic activity for other antibiotics. The enhanced photocatalytic activity of the ternary heterostructures was attributed to the full-spectrum response and the synergistic effect of the dual Z-type heterojunctions, which improved the visible light absorption and facilitated the charge separation. In addition, ˙OH and ˙O2- play a dominant role in the photodegradation process. This work contributes to the design of novel photocatalytic materials with dual Z-type heterojunctions and efficient photocatalysts for the degradation of antibiotics.