Photocatalytic Production Of Hydrogen Peroxide Research Articles

Nitrogen‐Rich Carbon Dot‐Mediated n→π* Electronic Transition in Carbon Nitride for Superior Photocatalytic Hydrogen Peroxide Production

AbstractSolar‐driven synthesis of hydrogen peroxide (H2O2) through photocatalysis stands out as a promising avenue for sustainable energy generation, marked by environmental friendliness and industrial feasibility. However, the inherent limitations of carbon nitride (CN) in photocatalytic H2O2 production significantly impede their performance. Herein, a novel 0D/2D carbon dots‐modified CN nanosheet heterojunction (CDsMCN) is introduced, synthesized through a hydrothermal‐calcination tandem strategy induced by CDs derived from melamine. This innovative technique enhances the n→π* electronic transition in CDsMCN, accelerating the separation efficiency of electron‐hole pairs, boosting oxygen adsorption, and promoting a highly selective 2e− ORR. Comparative to pristine CN, CDs10MCN exhibited a remarkable tenfold increase in H2O2 production, reaching an impressive 1.48 mmol L−1. Furthermore, CDs10MCN demonstrates exceptional stability, maintaining its catalytic efficiency at the initial level over four consecutive cycles. The notable achievement of a molar selectivity of H2O2 ≈80% at an onset potential of 0.6 V (vs RHE) underscores its exceptional ability to produce the desired product selectively. Advanced in situ characterization together with DFT calculations revealed that the ultrathin CDs10MCN nanosheet heterojunction with enhanced n→π* electronic transition improves its optical properties, reduces bandgap, facilitates fast charge migration, and increases photocatalytic H2O2 performance, thereby serving as a promising candidate for advanced catalytic applications.

Accelerated sonochemical fabrication of MIn2S4 (M = Zn, Mg, Ni, Co) for ultra-high photocatalytic hydrogen peroxide production

Ternary metal sulfide (MIn2S4) by virtue of large extinction coefficient, suitable band gap and stability, has been proposed as a candidate for photocatalytic synthesis hydrogen peroxide (H2O2). However, MIn2S4 is conventionally synthesized by solvothermal method that is generally characterized by tedious operational steps and long reaction time. In this work, four sonoMIn2S4 (M = Zn, Mg, Ni, Co) were successfully prepared by sonochemical method within 2 h. These as-synthesized sonoMIn2S4 delivered much high-efficient photocatalytic H2O2 generation. Particularly, the sonoZnIn2S4 presented a H2O2 production rate of 21295.5 μmol∙g−1∙h−1 in water/benzylalcohol system, which is 3.0 times that ZnIn2S4 prepared by solvothermal method. The remarkably improved photocatalytic performance of sonoZnIn2S4 might be due to the multiple defects and fast electron-hole pair separation caused by ultrasound cavitation effect. Other metal sulfide photocatalysts with high performance were efficiently fabricated by facile sonochemical technology as well. The sonochemical method realized the rapid preparation of metal sulfide photocatalysts and efficient production of H2O2, which benefits to meet the United Nations Sustainable Development Goals (SDGs) including SDG-7 and SDG-12.

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.

Photocatalytic Hydrogen Peroxide Production through Functionalized Semiconductive Metal-Organic Frameworks.

Hydrogen peroxide (H2O2) holds significance as a vital chemical with the potential to serve as an energy carrier. Compared with the conventional anthraquinone process, photocatalytic H2O2 production has emerged as an appealing alternative because of its energy efficiency and environmental sustainability. However, the existing photocatalysts suffer from low catalytic efficiency, limited tunability of optical properties, and reliance on sacrificial agents due to high energy loss caused by inefficient charge separation. Therefore, developing catalysts with tunable optical properties and efficient charge separation is desirable. In this work, we introduce postsynthetic functionalization into an electrically conductive metal-organic framework, namely, DPT-MOF. Leveraging DPT (3,6-di(4-pyridyl)-1,2,4,5-tetrazine) as a pillar ligand, we exploited click-type chemistry to manipulate band position and charge separation efficiency, allowing for photocatalytic nonsacrificial H2O2 production. Notably, the fluorine-functionalized MOF exhibited the highest H2O2 production rate of 1676 μmol g-1 h-1 under visible light in O2-saturated water among our other samples. This high production rate is attributed to the tuned electronic structure and prolonged charge lifetime facilitated by the fluorine groups. This work highlights the effectiveness of postsynthetic methodology in tuning optical properties, opening a promising avenue for advancing the field of semiconductive MOF-based photocatalysis.

Cyanide‐based Covalent Organic Frameworks for Enhanced Overall Photocatalytic Hydrogen Peroxide Production

AbstractPhotocatalytic oxygen reduction to produce hydrogen peroxide (H2O2) is a promising route to providing oxidants for various industrial applications. However, the lack of well‐designed photocatalysts for efficient overall H2O2 production in pure water has impeded ongoing research and practical thrusts. Here we present a cyanide‐based covalent organic framework (TBTN‐COFs) combining 2,4,6‐trimethylbenzene‐1,3,5‐tricarbonitrile (TBTN) and benzotrithiophene‐2,5,8‐tricarbaldehyde (BTT) building blocks with water‐affinity and charge‐separation. The ultrafast intramolecular electron transfer (<500 fs) and prolonged excited state lifetime (748 ps) can be realized by TBTN‐COF, resulting in a hole accumulated BTT and electron‐rich TBTN building block. Under one sun, the 11013 μmol h−1 g−1 yield rate of H2O2 can be achieved without any sacrificial agent, outperforming most previous reports. Furthermore, the DFT calculation and in situ DRIFTS spectrums suggesting a Yeager‐type absorption of *O2⋅− intermediate in the cyanide active site, which prohibits the formation of superoxide radical and revealing a favored H2O2 production pathway.

Cyanide-based Covalent Organic Frameworks for Enhanced Overall Photocatalytic Hydrogen Peroxide Production.

Photocatalytic oxygen reduction to produce hydrogen peroxide (H2O2) is a promising route to providing oxidants for various industrial applications. However, the lack of well-designed photocatalysts for efficient overall H2O2 production in pure water has impeded ongoing research and practical thrusts. Here we present a cyanide-based covalent organic framework (TBTN-COFs) combining 2,4,6-trimethylbenzene-1,3,5-tricarbonitrile (TBTN) and benzotrithiophene-2,5,8-tricarbaldehyde (BTT) building blocks with water-affinity and charge-separation. The ultrafast intramolecular electron transfer (<500 fs) and prolonged excited state lifetime (748 ps) can be realized by TBTN-COF, resulting in a hole accumulated BTT and electron-rich TBTN building block. Under one sun, the 11013 μmol h-1 g-1 yield rate of H2O2 can be achieved without any sacrificial agent, outperforming most previous reports. Furthermore, the DFT calculation and in situ DRIFTS spectrums suggesting a Yeager-type absorption of *O2⋅- intermediate in the cyanide active site, which prohibits the formation of superoxide radical and revealing a favored H2O2 production pathway.

Progress and perspective on covalent organic frameworks for photo-catalytic hydrogen peroxide production

Progress and perspective on covalent organic frameworks for photo-catalytic hydrogen peroxide production

Efficient photocatalytic hydrogen peroxide production over S-scheme In2S3/molten salt modified C3N5 heterojunction

Graphitic phase carbon nitride (g-C3N5), as a novel n-type metal-free material, is employed as a visible light-receptive catalyst because of its narrow band gap and abundant nitrogen. To overcome the low carrier mobility efficiency of g-C3N5, its modification by K ions was adopted. In addition, In2S3 was selected to couple with modified g-C3N5 to overcome the recombination of photogenerated e−/h+. As a novel photocatalytic material, it was proven to possess a high visible light absorption capacity and a strong H2O2 production ability (up to 3.89 mmol/L in 2 h). Moreover, a S-scheme heterojunction structure was successfully constructed between the two materials, which was tested and confirmed to be successful in raising the photogenerated e−/h+ separation efficiency. Ultimately, the primary processes of photocatalytic H2O2 production were summarized by superoxide radical and rotating disc electron measurements. This research provides a fresh perspective for the synthesis of C3N5-based S-scheme heterojunction photocatalysts for producing H2O2.

A quaternary ammonium cyclodextrin polymer for efficient photocatalytic production of hydrogen peroxide from pure water

A photocatalytic system can be used to efficiently produce hydrogen peroxide (H2O2) without introducing a sacrificial agent or oxygen (O2). This system has practical application potential but remains challenging to implement. To increase the H2O2 yield of this system, a quaternary ammonium cyclodextrin polymeric photocatalyst QCD36A1-1350 is successfully synthesized using quaternization modification and low-temperature polycondensation. The photocatalyst is used to produce H2O2 from pure water and air by the one-step two electron oxygen reduction reaction. Under irradiation by visible light, QCD36A1-1350 produces a higher H2O2 yield (of up to 2.51 mmol g−1h−1) than unquaternized polymers and reported metal-free catalysts under similar conditions. Experimental and theoretical studies clearly show that the introduction of quaternary ammonium groups can effectively broaden the visible light absorption of polymer catalysts, while increasing the hydrophilicity, charge transfer efficiency and surface stability. The practicability of efficient photocatalytic production of H2O2 is realized by increasing the activity and selectivity of the polymer photocatalyst.

Rationally Designed Cyclooctatetrathiophene-Based Porous Aromatic Frameworks (COTh-PAFs) for Efficient Photocatalytic Hydrogen Peroxide Production.

Constructing stable and efficient photocatalysts for H2 O2 production is of great importance and is challenging. In this study, the synthesis of three photoactive cyclooctatetrathiophene (COTh)-based porous aromatic frameworks (COTh-PAFs) in an alternating donor-acceptor (D-A) fashion is presented. In combination with a triazine-derived electron acceptor, PAF-363 exhibits high efficiency for the photosynthesis of H2 O2 with production rates of 11733 μmol g-1  h-1 (with sacrificial agent) and 3930 μmol g-1  h-1 (without sacrificial agent) from water and oxygen under visible light irradiation. Experimental results and theoretical calculations reveal that the charge transfer positions and the O2 adsorption sites in PAF-363 are both concentrated on COTh fragments, which facilitate the H2 O2 production through the oxygen reduction reaction (ORR) pathway. This work highlights that the rational design of COTh-PAFs with consideration of D-A direction, charge transfer positions, and O2 adsorption sites provides a feasible access to efficient H2 O2 production photocatalysts.

Rationally Designed Cyclooctatetrathiophene‐Based Porous Aromatic Frameworks (COTh‐PAFs) for Efficient Photocatalytic Hydrogen Peroxide Production

AbstractConstructing stable and efficient photocatalysts for H2O2 production is of great importance and is challenging. In this study, the synthesis of three photoactive cyclooctatetrathiophene (COTh)‐based porous aromatic frameworks (COTh‐PAFs) in an alternating donor‐acceptor (D−A) fashion is presented. In combination with a triazine‐derived electron acceptor, PAF‐363 exhibits high efficiency for the photosynthesis of H2O2 with production rates of 11733 μmol g−1 h−1(with sacrificial agent) and 3930 μmol g−1 h−1 (without sacrificial agent) from water and oxygen under visible light irradiation. Experimental results and theoretical calculations reveal that the charge transfer positions and the O2 adsorption sites in PAF‐363 are both concentrated on COTh fragments, which facilitate the H2O2 production through the oxygen reduction reaction (ORR) pathway. This work highlights that the rational design of COTh‐PAFs with consideration of D−A direction, charge transfer positions, and O2 adsorption sites provides a feasible access to efficient H2O2 production photocatalysts.

Mixed‐Linker Strategy for the Construction of Sulfone‐Containing D–A–A Covalent Organic Frameworks for Efficient Photocatalytic Hydrogen Peroxide Production

AbstractThe solar‐driven photocatalytic production of hydrogen peroxide (H2O2) from water and oxygen using semiconductor catalysts offers a promising approach for converting solar energy into storable chemical energy. However, the efficiency of photocatalytic H2O2 production is often restricted by the low photo‐generated charge separation, slow surface reactions and inadequate stability. Here, we developed a mixed‐linker strategy to build a donor‐acceptor‐acceptor (D–A–A) type covalent organic framework (COF) photocatalyst, FS‐OHOMe‐COF. The FS‐OHOMe‐COF structure features extended π–π conjugation that improves charge mobility, while the introduction of sulfone units not only as active sites facilitates surface reactions with water but also bolsters stability through increased interlayer forces. The resulting FS‐OHOMe‐COF has a low exciton binding energy, long excited‐state lifetime and high photo‐stability that leads to high performance for photocatalytic H2O2 production (up to 1.0 mM h−1) with an H2O2 output of 19 mM after 72 hours of irradiation. Furthermore, the catalyst demonstrates high stability, which sustained activity over 192 hours of photocatalytic experiment.

Mixed-Linker Strategy for the Construction of Sulfone-Containing D-A-A Covalent Organic Frameworks for Efficient Photocatalytic Hydrogen Peroxide Production.

The solar-driven photocatalytic production of hydrogen peroxide (H2 O2 ) from water and oxygen using semiconductor catalysts offers a promising approach for converting solar energy into storable chemical energy. However, the efficiency of photocatalytic H2 O2 production is often restricted by the low photo-generated charge separation, slow surface reactions and inadequate stability. Here, we developed a mixed-linker strategy to build a donor-acceptor-acceptor (D-A-A) type covalent organic framework (COF) photocatalyst, FS-OHOMe-COF. The FS-OHOMe-COF structure features extended π-π conjugation that improves charge mobility, while the introduction of sulfone units not only as active sites facilitates surface reactions with water but also bolsters stability through increased interlayer forces. The resulting FS-OHOMe-COF has a low exciton binding energy, long excited-state lifetime and high photo-stability that leads to high performance for photocatalytic H2 O2 production (up to 1.0 mM h-1 ) with an H2 O2 output of 19 mM after 72 hours of irradiation. Furthermore, the catalyst demonstrates high stability, which sustained activity over 192 hours of photocatalytic experiment.

N and O vacancies regulation over semiconductor heterojunction to synergistically boost photocatalytic hydrogen peroxide production

Defect engineering represents a potent strategy for the modification of electronic properties by introducing atomic vacancies in photocatalysts. However, the synergistic enhancement attributable to different types of atomic vacancies within a heterojunction, as well as their underlying mechanisms, remains sparsely studied. Here, the flexible g-C3N4 materials with varying nitrogen vacancies were prepared via a facile calcination method under different atmospheric conditions and then composited with CeO2 nanocubes to construct Z-scheme heterojunction. It was observed that CeO2 has abundant O vacancies, and the g-C3N4 form tertiary nitrogen defects at the center of the heptazine units under an NH3 atmosphere treatment. The resulting enhancement in the interfacial built-in electric field, coupled with the synergistic effect of O and N vacancies within the Z-scheme heterojunction, has been demonstrated to significantly enhance charge transfer efficiency. This results in an optimized photoactivity with a H2O2 generation rate of 2.01 mmol g–1 h–1. This work opens an avenue for constructing and optimizing the heterogeneous photocatalysts by defect engineering technology, and provides deep insight to understand the nature of vacancy engineering in designing effective catalysts for solar energy conversion.

Marrying luminescent metal nanoclusters to C3N4 for efficient photocatalytic hydrogen peroxide production

Photocatalytic oxygen (O2) reduction has been considered a promising method for hydrogen peroxide (H2O2) production. However, the poor visible light harvesting and low-efficient separation and generation of charge carriers of conventional photocatalysts strongly limited their photocatalytic H2O2 generation performance. Herein, we design a highly efficient photocatalyst in this work by marrying luminescent gold-silver nanoclusters (AuAg NCs) to polyethyleneimine (PEI) modified C3N4 (C3N4-PEI). The key design in this work is the utilization of highly luminescent AuAg NCs as photosensitizers to promote the generation and separation of charge carriers of C3N4-PEI, thereby ultimately producing abundant e− for O2 reduction under visible light illumination (λ ≥ 400 nm). As a result, the as-designed photocatalyst (C3N4-PEI-AuAg NCs) exhibits excellent photocatalytic activity with an H2O2 production capability of 82 μM in pure water, which is 3.5 times higher than pristine C3N4 (23 μM). This interesting design provides a paradigm in developing other high-efficient photocatalysts for visible-light-driven H2O2 production.

Extended H-bonds/π-bonds networks for boosting electron transfer over polydopamine-covered nanocellulose/g-C3N4 toward efficient photocatalytic H2O2 production

Photocatalytic hydrogen peroxide production (PHP) from H2O and O2 is a promising solar-to-chemical conversion technology. However, conventional doping, heterojunction and defect engineering of catalyst modification for enhanced PHP process is unable to meet the highly requirements of efficient oxygen reduction reaction (ORR), while also damaging the intrinsic crystal structure of the catalysts. Herein, we demonstrate a rationally extended H-bonds/π-bonds intermolecular networks between carbon nitride (g-C3N4, CN) and carboxylated cellulose nanofibers (CNF) with a small quantity of polydopamine (PDA) for solar H2O2 production. Ultimately, CN/CNFP exhibits an extraordinary PHP of 130.7 μmol·L−1·h−1, surpassing CN/CNF (75.2 μmol·L−1·h−1) and pure CN (20.1 μmol·L−1·h−1). Experimental and density function theory (DFT) have validated that CNFP increases the adsorption capabilities of O2, enhancing the efficiency of photogenerated charge transfer and separation via multiple hydrogen bonding/π-π stacking with g-C3N4, thereby facilitating the superior PHP via a two-step single-electron ORR pathway. This work offered a viable route to modulate directed transfer of photogenerated charges with multiple intermolecular interactions and presented an encouraging strategy to obtain high-efficient PHP.

Photocatalytic hydrogen peroxide production from seawater over graphitic carbon nitride supported titanium dioxide quantum dots

Photosynthesis of hydrogen peroxide (H2O2) from seawater, as a promising technique, is in infancy, and faces challenges of deactivation of photocatalyst and disturbance in H2O2 formation due to the coexisting salts in seawater. Herein, graphitic carbon nitride (g-C3N4) nanosheets supported titanium dioxide (TiO2) quantum dots (QDs) are exploited as novel and efficient photocatalysts for H2O2 photoproduction from seawater. An appropriate content of as-prepared TiO2 QDs are highly and uniformly dispersed on the surface of g-C3N4 nanosheets after a neutralization treatment. TiO2 QDs emerge the synergistic effect and the band gaps regulation effect on g-C3N4 to enhance the H2O2 production. The salt ions in the actual seawater also play the positive role. In actual seawater, the photocatalyst obtains 8.38 mM·h−1·g cat−1 of H2O2 productivity, 11.2% of apparent quantum yields (AQY), and good reusability·H2O2 productivity can be further increased into 30.15 and 23.44 mM·h−1·g cat−1, respectively in alkaline environment and with the addition of electron and proton donor ethanol in seawater. Active species and mechanism of the present photocatalytic system in seawater are also clearly clarified. TiO2 QDs supported on g-C3N4 photocatalyst achieved a major channel of two-electron reduction of O2, and an auxiliary channel of single electron reduction of O2 to produce H2O2 in seawater.

Dual Regulation of Charge Separation and the Oxygen Reduction Pathway by Encapsulating Phosphotungstic Acid into the Cationic Covalent Organic Framework for Efficient Photocatalytic Hydrogen Peroxide Production.

Previous research on covalent organic framework (COF)-based photocatalytic H2O2 synthesis from oxygen reduction focuses more on charge carrier separation but less on the electron utilization efficiency of O2. Herein, we put forward a facile approach to simultaneously promote charge separation and tailor the oxygen reduction pathway by introducing phosphotungstic acid (PTA) into the cationic COF skeleton. Experiments verified that PTA, as an electron transport medium, establishes a fast electron transfer channel from the COF semiconductor conductor band to the substrate O2; meanwhile, the reaction path is optimized by its catalytic cycle for preferable dioxygen capture and reduction in oxygen reduction reaction (ORR) kinetics. The existence of PTA promotes the rate and tendency of converting O2 into •O2- intermediates, which is conducive to boosting the photocatalytic activity and selectivity toward the sequential two-step single-electron ORR. As expected, compared to the pristine TTB-EB, the optimal PTA0.5@TTB-EB achieves a 2.2-fold improvement of visible-light-driven photocatalytic performance with a H2O2 production rate of 897.94 μmol·L-1·h-1 in pure water without using any sacrificial agents. In addition, owing to the robust electrostatic interaction and the confinement effect of porous TTB-EB channels, the PTA@TTB-EB composite possessed favorable stability.

Enhanced biomimetic catalysis via self-cascade photocatalytic hydrogen peroxide production over modified carbon nitride nanozymes for total antioxidant capacity evaluation

The peroxidase mimics usually requires the addition of exogenous hydrogen peroxide (H2O2), which greatly hinder their practical applications. Herein, through rational co-modification of multiple elements (potassium (K), chlorine (Cl) and iodine (I)), the modified carbon nitride nanomaterials (KCl/KI-CN) could serve as efficient bifunctional catalysts. The multiple elements doping and the incorporation of cyano groups (CN) are deemed to enhance their photocatalytic and peroxidase-like activity, respectively. Based on the photocatalytic function, H2O2 can be produced continuously and steadily via two-electron oxygen reduction over modified carbon nitride under visible light irradiation. Subsequently, the KCl/KI-CN could catalyze the chromogenic substrate by the in-situ produced H2O2. Taking advantage of the bifunctional properties of modified carbon nitride, we for the first time demonstrate a self-cascade catalytic process and apply successfully for the ascorbic acid (AA) detection and versatile total antioxidant capacity (TAC) evaluation. This paper not only prepares an efficiently bifunctional catalyst but also provides a new self-cascade photocatalytic H2O2 production strategy for the peroxidase-like application.

Carbon dots bridged Zn0.5Cd0.5S with interfacial amide bond facilitating electron transfer for efficient photocatalytic hydrogen peroxide production

Photocatalytic H2O2 production has gained significant attention as an environmentally friendly approach. The key is to explore efficient photocatalysts with sufficient active sites and excellent electron transfer capacity. Herein, we propose a novel approach by incorporating carbon dots (CDs) on ethylenediamine capped Zn0.5Cd0.5S, which was bridged with an interfacial amide bond. Smooth transfer of photoinduced electrons from Zn0.5Cd0.5S to carbon dots via a high-speed electron channel is afforded by interfacial amide bond. A remarkable H2O2 yield with a rate of 252 μmol/h and an apparent quantum yield (AQY) of 31 % at 400 nm is achieved. Photoelectrochemical analysis and density function theory (DFT) calculation reveal CDs with abundant oxygenous functional groups as active sites, boosting activity and selectivity. This interfacial engineering strategy with the acceleration of electrons transfer and enhanced 2e- selectivity can be applied to advanced photocatalytic systems for the achievement of valuable organics, environmental purification and new energy carriers.