Nanospatial Charge Modulation of Monodispersed Polymeric Microsphere Photocatalysts for Exceptional Hydrogen Peroxide Production

H2O2 Photosynthesis from H2O and O2 under Weak Light by Carbon Nitrides with the Piezoelectric Effect

Driven by the essential need of a green, safe, and low-cost approach to producing H2O2, a highly valuable multifunctional chemical, artificial photosynthesis emerges as a promising avenue. However, current catalyst systems remain challenging, due to the need of high-density sunlight, poor selectivity and activity, or/and unfavorable thermodynamics. Here, we reported that an indirect 2e- water oxidation reaction (WOR) in photocatalytic H2O2 production was unusually activated by C5N2 with piezoelectric effects. Interestingly, under ultrasonication, C5N2 exhibited an overall H2O2 photosynthesis rate of 918.4 μM/h and an exceptionally high solar-to-chemical conversion efficiency of 2.6% after calibration under weak light (0.1 sun). Mechanism studies showed that the piezoelectric effect of carbon nitride overcame the high uphill thermodynamics of *OH intermediate generation, which enabled a new pathway for 2e- WOR, the kinetic limiting step in the overall H2O2 production from H2O and O2. Benefiting from the outstanding sonication-assisted photocatalytic H2O2 generation under weak light, the concept was further successfully adapted to biomedical applications in efficient sono-photochemodynamic therapy for cancer treatment and water purification.

Nanoengineering of Porous 2D Structures with Tunable Fluid Transport Behavior for Exceptional H2O2 Electrosynthesis

Precision nanoengineering of porous two-dimensional structures has emerged as a promising avenue for finely tuning catalytic reactions. However, understanding the pore-structure-dependent catalytic performance remains challenging, given the lack of comprehensive guidelines, appropriate material models, and precise synthesis strategies. Here, we propose the optimization of two-dimensional carbon materials through the utilization of mesopores with 5-10 nm diameter to facilitate fluid acceleration, guided by finite element simulations. As proof of concept, the optimized mesoporous carbon nanosheet sample exhibited exceptional electrocatalytic performance, demonstrating high selectivity (>95%) and a notable diffusion-limiting disk current density of -3.1 mA cm-2 for H2O2 production. Impressively, the electrolysis process in the flow cell achieved a production rate of 14.39 mol gcatalyst-1 h-1 to yield a medical-grade disinfectant-worthy H2O2 solution. Our pore engineering research focuses on modulating oxygen reduction reaction activity and selectivity by affecting local fluid transport behavior, providing insights into the mesoscale catalytic mechanism.

Solar-to-H2 O2 Catalyzed by Covalent Organic Frameworks

Benefiting from the excellent structural tunability, robust framework, ultrahigh porosity, and rich active sites, covalent organic frameworks (COFs) are widely recognized as promising photocatalysts in chemical conversions, and emerged in the hydrogen peroxide (H2 O2 ) photosynthesis in 2020. H2 O2 , serving as an environmental-friendly oxidant and a promising liquid fuel, has attracted increasing researchers to explore its potential. Over the past few years, numerous COFs-based photocatalysts are developed with encouraging achievements in H2 O2 production, whereas no comprehensive review articles exist to summarize this specific and significant area. Herein we provide a systematic overview of the advances and challenges of COFs in photocatalytic H2 O2 production. We first introduce the priorities of COFs in H2 O2 photosynthesis. Then, various strategies to improve COFs photocatalytic efficiency are discussed. The perspective and outlook for future advances of COFs in this emerging field are finally offered. This timely review will pave the way for the development of highly efficient COFs photocatalysts for practical production of value-added chemicals not limited to H2 O2 .

Synergistic Promotion of the Photocatalytic Preparation of Hydrogen Peroxide (H2 O2 ) from Oxygen by Benzoxazine and Si─O─Ti Bond

Hydrogen peroxide (H2 O2 ) is considered one of the most important chemical products and has a promising future in photocatalytic preparation, which is green, pollution-free, and hardly consumes any non-renewable energy. This study involves the preparation of benzoxazine with Si─O bonds via the Mannich reaction, followed by co-hydrolysis to produce photocatalysts containing benzoxazine with Si─O─Ti bonds. In this study, a benzoxazine photocatalyst with Si─O─Ti bonds is synthesized and characterized using fourier transform infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The size and elemental distribution of the nanoparticles are confirmed by transmission electron microscopy and scanning electron microscopy. The photocatalytic synthesis of H2 O2 is tested using the titanium salt detection method, and the rate is found to be 7.28 µmol h-1 . Additionally, the catalyst exhibits good hydrolysis resistance and could be reused multiple times. The use of benzoxazine with Si─O─Ti bonds presents a promising experimental and theoretical foundation for the industrial production of H2 O2 through photocatalytic synthesis.

Spatial Specific Janus S-Scheme Photocatalyst with Enhanced H2 O2 Production Performance

Photocatalytic oxygen reduction reaction (ORR) for H₂ O₂ production in the absence of sacrificing agents is a green approach and of great significance, where the design of photocatalysts with high performance is the central task. Herein, a spatial specific S-scheme heterojunction design by introducing a novel semiconducting pair with a S-scheme mechanism in a purpose-designed Janus core-shell-structured hollow morphology is reported. In this design, TiO₂ nanocrystals are grown inside the inner wall of resorcinol-formaldehyde (RF) resin hollow nanocakes with a reverse bumpy ball morphology (TiO₂ @RF). The S-scheme heterojunction preserves the high redox ability of the TiO₂ and RF pair, the spatial specific Janus design enhances the charge separation, promotes active site exposure, and reduces the H₂ O₂ decomposition to a large extent. The TiO₂ @RF photocatalyst shows a high H₂ O₂ yield of 66.6 mM g^-1  h^-1 and solar-to-chemical conversion efficiency of 1.11%, superior to another Janus structure (RF@TiO₂ ) with the same heterojunction but a reversed Janus spatial arrangement, and most reported photocatalysts under similar reaction conditions. The work has paved the way toward the design of next-generation photocatalysts for green synthesis of H₂ O₂ production.

Molecular Level Modulation of Anthraquinone-containing Resorcinol-formaldehyde Resin Photocatalysts for H2 O2 Production with Exceeding 1.2 % Efficiency

Designing polymeric photocatalysts at the molecular level to modulate the photogenerated charge behavior is a promising and challenging strategy for efficient hydrogen peroxide (H₂ O₂ ) photosynthesis. Here, we introduce electron-deficient 1,4-dihydroxyanthraquinone (DHAQ) into the framework of resorcinol-formaldehyde (RF) resin, which modulates the donor/acceptor ratio from the perspective of molecular design for promoting the charge separation. Interestingly, H₂ O₂ can be produced via oxygen reduction and water oxidation pathways, verified by isotopic labeling and in situ characterization techniques. Density functional theory (DFT) calculations elucidate that DHAQ can reduce the energy barrier for H₂ O₂ production. RF-DHAQ exhibits excellent overall photosynthesis of H₂ O₂ with a solar-to-chemical conversion (SCC) efficiency exceeding 1.2 %. This work opens a new avenue to design polymeric photocatalysts at the molecular level for high-efficiency artificial photosynthesis.

Solar-to-H2 O2 Energy Conversion by the Photothermal Effect of a Polymeric Photocatalyst via a Two-Channel Pathway

With a view to using solar energy, the exploitation of near-infrared (NIR) light, which constitutes about 50 % of solar energy, in photocatalytic H₂ O₂ synthesis remains challenging. In this study, resorcinol-formaldehyde (RF), which has a relatively low bandgap and high conductivity, is introduced for photothermal catalytic generation of H₂ O₂ under ambient conditions. Owing to the promoted surface charge transfer rate under high temperature, the photosynthetic yield reaches roughly 2000 μm within 40 min under 400 mW cm^-2 irradiation with a solar-to-chemical conversion (SCC) efficiency of up to 0.19 % at 338 K under ambient conditions, exceeding the rate of photocatalysis with a cooling system by a factor of about 2.5. Notably, the H₂ O₂ produced by RF during photothermal process was formed via a two-channel pathway, leading to the overall promotion of H₂ O₂ formation. The resultant H₂ O₂ can be applied in situ for pollutant removal. This work offers a sustainable and economical route for the efficient formation of H₂ O₂ .

A general interfacial-energetics-tuning strategy for enhanced artificial photosynthesis

The demands for cost-effective solar fuels have triggered extensive research in artificial photosynthesis, yet the efforts in designing high-performance particulate photocatalysts are largely impeded by inefficient charge separation. Because charge separation in a particulate photocatalyst is driven by asymmetric interfacial energetics between its reduction and oxidation sites, enhancing this process demands nanoscale tuning of interfacial energetics on the prerequisite of not impairing the kinetics and selectivity for surface reactions. In this study, we realize this target with a general strategy involving the application of a core/shell type cocatalyst that is demonstrated on various photocatalytic systems. The promising H₂O₂ generation efficiency validate our perspective on tuning interfacial energetics for enhanced charge separation and photosynthesis performance. Particularly, this strategy is highlighted on a BiVO₄ system for overall H₂O₂ photosynthesis with a solar-to-H₂O₂ conversion of 0.73%.

Metal-Free Photocatalysts for Conversion of H2 O into Hydrogen Peroxide

Hydrogen peroxide (H₂ O₂ ) is an important green oxidizing agent for environmental protection and chemical production. In comparison to the traditional anthraquinone method, photosynthesis is a green and energy-saving process for H₂ O₂ production. To improve the stability and practical application value of the H₂ O₂ synthesized by photocatalysis, the H₂ O₂ photosynthesis should be conducted in pure water without involving any sacrificial reagents. In this regard, organic semiconducting catalysts pose as a suitable candidate for photocatalytic H₂ O₂ synthesis owing to their metal-free nature to prevent H₂ O₂ decomposition by the metal ions. In this Perspective, the H₂ O₂ photosynthesis history is firstly introduced, followed by a review of the organic semiconductor photocatalysts reported to date. Finally, the main problems to thwart the advances of current pure H₂ O-to-H₂ O₂ photosynthesis are discussed, followed by proposed solutions to address these issues in order to pave new ways for the development of highly efficient metal-free organic photocatalysts for sustainable pure H₂ O-to-H₂ O₂ conversion.

Extended Conjugation Tuning Carbon Nitride for Non-sacrificial H2 O2 Photosynthesis and Hypoxic Tumor Therapy

Artificial photocatalysis offers a clean approach for producing H₂ O₂ . However, the poor selectivity and activity of H₂ O₂ production hamper traditional industrial applications and emerging photodynamic therapy (PDT)/chemodynamic therapy (CDT). Herein, we report a C₅ N₂ photocatalyst with a conjugated C=N linkage for selective and efficient non-sacrificial H₂ O₂ production in both normoxic and hypoxic systems. The strengthened delocalization of π-electrons by linkers in C₅ N₂ downshifted the band position, thermodynamically eliminating side H₂ evolution reaction and kinetically promoting water oxidation. As a result, C₅ N₂ had a competitive solar-to-chemical conversion efficiency of 0.55 % in overall H₂ O₂ production and exhibited by far the highest activity under hypoxic conditions (698 μM h^-1 ). C₅ N₂ was further applied to hypoxic PDT/CDT with outstanding performance in apparent cancer cell death and synchronous bioimaging. The study sheds light on the photosynthesis of H₂ O₂ by carbon nitrides for health applications.

Versatile synthesis of dendritic mesoporous rare earth-based nanoparticles

Rare earth-based nanomaterials that have abundant optical, magnetic, and catalytic characteristics have many applications. The controllable introduction of mesoporous channels can further enhance its performance, such as exposing more active sites of rare earth and improving the loading capacity, yet remains a challenge. Here, we report a universal viscosity-mediated assembly strategy and successfully endowed rare earth-based nanoparticles with central divergent dendritic mesopores. More than 40 kinds of dendritic mesoporous rare earth-based (DM-REX) nanoparticles with desired composition (single or multiple rare earth elements, high-entropy compounds, etc.), particle diameter (80 to 500 nanometers), pore size (3 to 20 nanometers), phase (amorphous hydroxides, crystalline oxides, and fluorides), and architecture were synthesized. Theoretically, a DM-REX nanoparticle library with 393,213 kinds of possible combinations can be constructed on the basis of this versatile method, which provides a very broad platform for the application of rare earth-based nanomaterials with rational designed functions and structures.

Molecularly Engineered Covalent Organic Frameworks for Hydrogen Peroxide Photosynthesis

Synthesizing H2 O2 from water and air via a photocatalytic approach is ideal for efficient production of this chemical at small-scale. However, the poor activity and selectivity of the 2 e- water oxidation reaction (WOR) greatly restricts the efficiency of photocatalytic H2 O2 production. Herein we prepare a bipyridine-based covalent organic framework photocatalyst (denoted as COF-TfpBpy) for H2 O2 production from water and air. The solar-to-chemical conversion (SCC) efficiency at 298 K and 333 K is 0.57 % and 1.08 %, respectively, which are higher than the current reported highest value. The resulting H2 O2 solution is capable of degrading pollutants. A mechanistic study revealed that the excellent photocatalytic activity of COF-TfpBpy is due to the protonation of bipyridine monomer, which promotes the rate-determining reaction (2 e- WOR) and then enhances Yeager-type oxygen adsorption to accelerate 2 e- one-step oxygen reduction. This work demonstrates, for the first time, the COF-catalyzed photosynthesis of H2 O2 from water and air; and paves the way for wastewater treatment using photocatalytic H2 O2 solution.

Dendrimer-Modified Silica Nanoparticles for Efficient Enrichment of Low-Concentration Peptides

Peptide profiling based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is of particular interest as it can provide physiologically and pathologically related information of the bio-samples. Due to the complexity of real biological samples, MALDI-TOF MS-based peptide mapping methods rely strongly on particular enrichment methods to improve the signal intensity. This paper introduces third-generation dendrimer-modified SBA-15 with the surface functionalization of amino and carboxyl group, respectively (denoted as SBA-15/G3-NH₂ and SBA-15/G3-COOH), for the efficient capture of low-abundance peptides. The enrichment ability of the nanocomposites was evaluated by standard peptides digests and real biological samples. The synthesized nanocomposites incorporated the benefit of dendrimers and mesoporous silica nanomaterial SBA-15, showing enhanced peptide enrichment ability. Therefore, this work may provide a new class of nanomaterials for peptide mapping from biological samples.

A biomimetic all-inorganic photocatalyst for the artificial photosynthesis of hydrogen peroxide

The artificial photosynthesis of H2O2 from water and O2 presents a sustainable route for the production. Remarkable progress in the rate of reaction has recently been achieved mainly by using...