Showing papers on "Photochemistry published in 2023"

Construction of dual Z-scheme Bi2WO6/g-C3N4/black phosphorus quantum dots composites for effective bisphenol A degradation.

Abstract: In this work, a novel dual Z-scheme Bi2WO6/g-C3N4/black phosphorus quantum dots (Bi2WO6/g-C3N4/BPQDs) composites were fabricated and utilized towards photocatalytic degradation of bisphenol A (BPA) under visible-light irradiation. Optimizing the content of g-C3N4 and BPQDs in Bi2WO6/g-C3N4/BPQDs composites to a suitable mass ratio can enhance the visible-light harvesting capacity and increase the charge separation efficiency and the transfer rate of excited-state electrons and holes, resulting in much higher photocatalytic activity for BPA degradation (95.6%, at 20 mg/L in 120 min) than that of Bi2WO6 (63.7%), g-C3N4 (25.0%), BPQDs (8.5%), and Bi2WO6/g-C3N4 (79.6%), respectively. Radical trapping experiments indicated that photogenerated holes (h+) and superoxide radicals (•O2-) played crucial roles in photocatalytic BPA degradation. Further, the possible degradation pathway and photocatalytic mechanism was proposed by analyzing the BPA intermediates. This work also demonstrated that the Bi2WO6/g-C3N4/BPQDs as effective photocatalysts was stable and have promising potential to remove environmental contaminants from real water samples.

Fast Au-Ni@ZIF-8-catalyzed ammonia borane hydrolysis boosted by dramatic volcano-type synergy and plasmonic acceleration

Abstract: Production of hydrogen (H2) from H2 storage materials is very attractive as a source of sustainable energy. We report that [email protected] alloys are very efficient nanocatalysts for H2 evolution upon ammonia borane hydrolysis under visible-light illumination with turnover frequency 3.4 times higher than with the monometallic Ni catalyst in the dark. This improvement is attributed to dramatic volcano-type positive synergy optimized in Au0.5Ni0.5 @ZIF-8, for which ZIF-8 is by far the superior support, as well as to the localized surface plasmon resonance induced between 450 and 620 nm. Infrared spectra analysis and tandem reaction confirm the origin of the hydrogen atoms, reveal the reaction mechanism, and suggest how the cleavage of the B–H and O–H bonds proceeds in this reaction. Deuteration experiments with D2O including primary kinetic isotope effects and density functional theory calculation under both dark and visible light conditions show that activation of H2O always is the rate-determining step.

Single-atom copper embedded in two-dimensional MXene toward peroxymonosulfate activation to generate singlet oxygen with nearly 100% selectivity for enhanced Fenton-like reactions

Abstract: Singlet oxygen (1O2)-dominated advanced oxidation processes has drawn widespread attention for selective oxidation of organic pollutants in complex water environments. However, the high efficiency and selectivity of 1O2 generation remains challenging. Herein, we develop single-atom copper anchored on Ti3C2Tx MXene nanosheets (Cu-SA/MXene) by molten salt etching for the generation of 1O2 via peroxymonosulfate (PMS) activation. Particularly, it exhibits a high selectivity of 99.71% toward 1O2 generation by activating PMS, which shows outstanding catalytic activity for multiple pollutants, and strong resistance to inorganic anions. Experimental and theoretical results reveal that the Cu single atoms with three oxygen coordination environments (Cu-O3) are more favorable for PMS absorption and selectively adsorb the terminal oxygen of PMS to promote the generation of SO5.-, resulting in the generation of 1O2. A continuous-flow wastewater system by dispersing catalysts on poly (vinylidene fluoride) membrane exhibit stable catalytic activity for polycarbonate plant wastewater treatment over 8 h.

Dynamic rhenium dopant boosts ruthenium oxide for durable oxygen evolution

Abstract: Heteroatom-doping is a practical means to boost RuO2 for acidic oxygen evolution reaction (OER). However, a major drawback is conventional dopants have static electron redistribution. Here, we report that Re dopants in Re0.06Ru0.94O2 undergo a dynamic electron accepting-donating that adaptively boosts activity and stability, which is different from conventional dopants with static dopant electron redistribution. We show Re dopants during OER, (1) accept electrons at the on-site potential to activate Ru site, and (2) donate electrons back at large overpotential and prevent Ru dissolution. We confirm via in situ characterizations and first-principle computation that the dynamic electron-interaction between Re and Ru facilitates the adsorbate evolution mechanism and lowers adsorption energies for oxygen intermediates to boost activity and stability of Re0.06Ru0.94O2. We demonstrate a high mass activity of 500 A gcata.-1 (7811 A gRe-Ru-1) and a high stability number of S-number = 4.0 × 106 noxygen nRu-1 to outperform most electrocatalysts. We conclude that dynamic dopants can be used to boost activity and stability of active sites and therefore guide the design of adaptive electrocatalysts for clean energy conversions.

Interfacial Chemical Bond and Oxygen Vacancy‐Enhanced In2O3/CdSe‐DETA S‐scheme Heterojunction for Photocatalytic CO2 Conversion

Abstract: The S‐scheme heterojunctions have great potential for photocatalytic carbon dioxide reduction due to their unique carrier migration pathways, superior carrier separation efficiencies, and high redox capacities. However, the precise process of the oriented powerful electron transport remains a great challenge. Herein, an InOCd bond‐modulated S‐scheme heterojunction of In2O3/CdSe‐DETA is synthesized by a simple microwave‐assisted hydrothermal method for the accelerated photogenerated electron transfer. Meanwhile, the oxygen vacancies (Vo) of In2O3 have an electron capture effect. Consequently, thanks to the synergistic effect of this In‐Vo‐In‐O‐Cd structural units at the interface, electrons are extracted and rapidly transferred to the surface‐active sites, which improves the electronic coupling of CO2. This finding precisely adjusts the electron transfer pathway and shortens the electron transfer distance. The synergistic effect of this chemical bond established in the S‐scheme heterostructure with oxygen vacancies in In2O3 (Vo‐In2O3) provides new insights into photocatalytic CO2 reduction.

BiOBr/MXene/gC3N4 Z-scheme heterostructure photocatalysts mediated by oxygen vacancies and MXene quantum dots for tetracycline degradation: Process, mechanism and toxicity analysis

Abstract: The rapid recombination rate of photogenerated charges make the rational design of high-performance stable photocatalysts challenging. Herein, the features of heterojunctions, oxygen vacancies (OVs), and MXene quantum dots (MQDs) were simultaneously collected in CBM (gC3N4/BiOBr/MXene) using a simple solvothermal method for the first time. OVs promoted the chemisorption of O2, MQDs not only accelerated electron transport but also promoted a photogenerated charge to selectively generate singlet oxygen, 99% of the tetracycline hydrochloride (TC-HCl) was degraded by CBM within 30 min under visible light irradiation. Thirteen intermediates and possible photocatalytic degradation pathways were proposed. It was discovered that CBM is nontoxic to the environment but can swiftly produce an excellent antibacterial effect when exposed to visible light irradiation. This research provides fresh insights into the effective removal of organic pollutants from water by combining cutting-edge defect engineering and quantum dot doping technology in photocatalytic heterojunctions.

Derivatized Benzothiazoles as Two-Photon-Absorbing Organic Photosensitizers Active under Near Infrared Light Irradiation.

Abstract: Homogeneous organic photocatalysis typically requires molecular photosensitizers absorbing in the ultraviolet-visible (UV/vis) region, because UV/vis photons possess the sufficient energy to excite those one-photon-absorbing photosensitizers to the desired excited states. However, UV/vis light irradiation has many potential limitations, especially for large-scale applications, such as low penetration through reaction media, competing absorption by substrates and co-catalysts, and incompatibility with substrates bearing light-sensitive functionalities. In fact, these drawbacks can be effectively avoided if near infrared (NIR) photons can be utilized to drive the target reactions. Herein, we report two benzothiazole-derived compounds as novel two-photon-absorbing (TPA) organic photosensitizers, which can function under NIR light irradiation using inexpensive LED as the light source. We demonstrate that by judicially modulating the donor-π-acceptor-π-donor-conjugated structure containing a bibenzothiazole core and imine bridges, excellent two-photon absorption capability in the NIR region can be achieved, approaching 2000 GM at 850 nm. Together with large quantum yields (∼0.5), these benzothiazole-derived TPA organic photosensitizers exhibit excellent performance in driving various O2-involved organic reactions upon irradiation at 850 nm, showing great penetration depth, superior to that upon blue light irradiation. A suite of photophysical and computational studies were performed to shed light on the underlying electronic states responsible for the observed TPA capability. Overall, this work highlights the promise of developing Ru/Ir-free organic photosensitizers operative in the NIR region by taking advantage of the two-photon absorption mechanism.

Enabling Specific Photocatalytic Methane Oxidation by Controlling Free Radical Type.

Abstract: Selective CH4 oxidation to CH3OH or HCHO with O2 in H2O under mild conditions provides a desired sustainable pathway for synthesis of commodity chemicals. However, manipulating reaction selectivity while maintaining high productivity remains a huge challenge due to the difficulty in the kinetic control of the formation of a desired oxygenate against its overoxidation. Here, we propose a highly efficient strategy, based on the precise control of the type of as-formed radicals by rational design on photocatalysts, to achieve both high selectivity and high productivity of CH3OH and HCHO in CH4 photooxidation for the first time. Through tuning the band structure and the size of active sites (i.e., single atoms or nanoparticles) in our Au/In2O3 catalyst, we show alternative formation of two important radicals, •OOH and •OH, which leads to distinctly different reaction paths to the formation of CH3OH and HCHO, respectively. This approach gives rise to a remarkable HCHO selectivity and yield of 97.62% and 6.09 mmol g-1 on In2O3-supported Au single atoms (Au1/In2O3) and an exceptional CH3OH selectivity and yield of 89.42% and 5.95 mmol g-1 on In2O3-supported Au nanoparticles (AuNPs/In2O3), respectively, upon photocatalytic CH4 oxidation for 3 h at room temperature. This work opens a new avenue toward efficient and selective CH4 oxidation by delicate design of composite photocatalysts.

Novel preparation strategy of graphdiyne (CnH2n-2): One-pot conjugation and S-Scheme heterojunctions formed with MoP characterized with in situ XPS for efficiently photocatalytic hydrogen evolution

Abstract: As a new two-dimensional (2D) carbon hybrid material, graphdiyne has attracted much attention for its good electrical conductivity, tunable electronic structure and special electron transfer enhancement properties. With its unique atomic arrangement and 2D network of sp and sp2 conjugated hybridization, graphdiyne has a natural advantage in building active catalytic sites. Meanwhile, its special charge distribution gives graphdiyne the ability to be an electron acceptor or donor. Due to its special properties, it has great potential in the field of hydrogen evolution for photocatalytic water decomposition. In this work, a novel strategy for the simple synthesis of graphdiyne (CnH2n-2) by CaC2, hexabromobenzene and mixed organic solvents was firstly prepared and effectively enhanced the photocatalytic hydrogen evolution by topological semimetals (MoP). Combined with experimental tools such as in situ XPS, EPR and DFT calculations, the possible formation of S-Scheme heterojunctions between graphdiyne and MoP is proposed as an important strategy for the application of graphdiyne in the field of photocatalytic hydrogen evolution.

Silver nanoparticle enhanced metal-organic matrix with interface-engineering for efficient photocatalytic hydrogen evolution

Abstract: Abstract Integrating plasmonic nanoparticles into the photoactive metal-organic matrix is highly desirable due to the plasmonic near field enhancement, complementary light absorption, and accelerated separation of photogenerated charge carriers at the junction interface. The construction of a well-defined, intimate interface is vital for efficient charge carrier separation, however, it remains a challenge in synthesis. Here we synthesize a junction bearing intimate interface, composed of plasmonic Ag nanoparticles and matrix with silver node via a facile one-step approach. The plasmonic effect of Ag nanoparticles on the matrix is visualized through electron energy loss mapping. Moreover, charge carrier transfer from the plasmonic nanoparticles to the matrix is verified through ultrafast transient absorption spectroscopy and in-situ photoelectron spectroscopy. The system delivers highly efficient visible-light photocatalytic H 2 generation, surpassing most reported metal-organic framework-based photocatalytic systems. This work sheds light on effective electronic and energy bridging between plasmonic nanoparticles and organic semiconductors.