Coating Polymeric Carbon Nitride on Conductive Carbon Cloth to Promote Charge Separation for Photocatalytic Water Splitting

Construction of carbon nitride/zeolitic imidazolate framework-67 heterojunctions on carbon fiber cloth as the photocatalyst for various pollutants removal and hydrogen production

With the macroscale and conductive carbon fiber cloth (CFC) as the substrate, the obtained self-supported photocatalysts hold great promise for enhancing the separation of generated carriers and the recyclability of catalysts, thereby improving the photocatalytic performance and practicality in various applications. Additionally, decorating metal-organic frameworks (MOFs) with ultrahigh surface area on the surface of effective semiconductors is a promising method to enhance the adsorption capacity and photocatalytic performance. Herein, zeolitic imidazolate framework-67 (ZIF-67) as a typical MOFs was applied to modify carbon nitride (C3N4) on the surface of macroscale and conductive CFC. CFC/C3N4/ZIF-67 (4 × 4 cm2) was obtained by a thermal condensation-chemical bath deposition two-step route, and it shows superior adsorption and photocatalytic activity toward bisphenol A (BPA), levofloxacin (LVFX), ciprofloxacin (CIP) and good hydrogen evolution activity. Besides, the recycling test for four cycles indicates the high stability of CFC/C3N4/ZIF-67 with an easy recycling process. In this study, CFC/C3N4/ZIF-67 was prepared through the hydrothermal and chemical bath deposition two-step method, which enhances light absorption and photocatalytic performance, as well as recyclability for solving environmental and energy issues.

Driving a NiTiO3 photocatalyst for the oxygen evolution reaction with near-infrared light

A nickel titanate (NTO) photocatalyst has been developed for the oxygen evolution reaction (OER) with an exceptionally broad light wavelength excitation ranging from visible to infrared. Specifically, by loading CoOx as the co-catalyst, the apparent quantum yields for the OER were ca. 2.2%, 1.0%, and 0.8% at wavelengths of 470, 760, and 850 nm, respectively. The achievements reveal that the NTO photocatalyst is highly efficient even under illumination with near-infrared (NIR) light, which confers the potential for highly efficient solar-driven oxidation reactions.

Piezoelectric built-in electric field advancing TiO2 for highly efficient photocatalytic air purification

Photocatalytic air purification is a promising technology; however, it suffers from a limited rate of photocatalytic mineralization (easily inactivated surfactant sites of hydroxyls) and poor kinetics of degradation. Herein, we report a ferroelectric strategy, employing a polyvinylidene fluoride (PVDF) layer embedded with TiO2, where the polarization field of stretched PVDF dramatically enhances and stabilizes active adsorption sites for the promotion of charge separation. The F (-) and H (+) atomic layers with distinct local structures in stretched PVDF increase the electron cloud density around Ti which simultaneously promotes the dissociation of water to form hydroxyl groups which are easier to activate for adsorption of formaldehyde molecules. Besides, the ferroelectric field of stretched PVDF effectively separates the photogenerated charge carriers and facilitates the carriers' transportation of TiO2/PVDF. The optimal stretched TiO2/PVDF exhibits excellent photocatalytic mineralization for formaldehyde with considerable stability. This work may evolve the polarization field as a new method to enhance adsorption and activation of hydroxyls and disclose the mechanism by which hydroxyl radicals mineralize gaseous formaldehyde for photocatalytic air purification.

Construction and Activity of an All-Organic Heterojunction Photocatalyst Based on Melem and Pyromellitic Dianhydride

The separation efficiency of photogenerated carriers in the g-C₃ N₄ system could be improved by the construction of all-organic heterojunctions. However, g-C₃ N₄ has a large π-π conjugated plane that induces a low number of amino groups (-NH₂ ), which are the sites of the heterojunction reaction with organic molecules. In this case, few heterojunction knots can be constructed, and the enhancement effect of the heterojunction cannot be fully displayed. In this study, an all-organic heterojunction with PMDA is constructed with melem instead of g-C₃ N₄ . Although the photocatalytic activity of melem is far below that of g-C₃ N₄ , the photocatalytic activity of PI (the all-organic heterojunction constructed with melem) is considerably higher than that of CP (the all-organic heterojunction constructed with g-C₃ N₄ ). This result is attributed to melem that has more -NH₂ groups to form more heterojunction knots, which can enable the effective transfer and separation of electron-hole pairs. These new findings may shed light on the design of all-organic heterojunction photocatalysts.

Tunable Carrier Transfer of Polymeric Carbon Nitride with Charge-Conducting CoV2O6∙2H2O for Photocatalytic O2 Evolution

Photocatalytic water splitting is one of the promising approaches to solving environmental problems and energy crises. However, the sluggish 4e⁻ transfer kinetics in water oxidation half-reaction restricts the 2e⁻ reduction efficiency in photocatalytic water splitting. Herein, cobalt vanadate-decorated polymeric carbon nitride (named CoVO/PCN) was constructed to mediate the carrier kinetic process in a photocatalytic water oxidation reaction (WOR). The photocatalysts were well-characterized by various physicochemical techniques such as XRD, FT-IR, TEM, and XPS. Under UV and visible light irradiation, the O₂ evolution rate of optimized 3 wt% CoVO/PCN reached 467 and 200 μmol h⁻¹ g⁻¹, which were about 6.5 and 5.9 times higher than that of PCN, respectively. Electrochemical tests and PL results reveal that the recombination of photogenerated carriers on PCN is effectively suppressed and the kinetics of WOR is significantly enhanced after CoVO introduction. This work highlights key features of the tuning carrier kinetics of PCN using charge-conducting materials, which should be the basis for the further development of photocatalytic O₂ reactions.

Semiconducting Polymers for Oxygen Evolution Reaction under Light Illumination

Sunlight-driven water splitting to produce hydrogen fuel has stimulated intensive scientific interest, as this technology has the potential to revolutionize fossil fuel-based energy systems in modern society. The oxygen evolution reaction (OER) determines the performance of overall water splitting owing to its sluggish kinetics with multielectron transfer processing. Polymeric photocatalysts have recently been developed for the OER, and substantial progress has been realized in this emerging research field. In this Review, the focus is on the photocatalytic technologies and materials of polymeric photocatalysts for the OER. Two practical systems, namely, particle suspension systems and film-based photoelectrochemical systems, form two main sections. The concept is reviewed in terms of thermodynamics and kinetics, and polymeric photocatalysts are discussed based on three key characteristics, namely, light absorption, charge separation and transfer, and surface oxidation reactions. A satisfactory OER performance by polymeric photocatalysts will eventually offer a platform to achieve overall water splitting and other advanced applications in a cost-effective, sustainable, and renewable manner using solar energy.

Development of dual-functional catalysis for hydrazine oxidation by an organic p-n bilayer through in situ formation of a silver co-catalyst

Dual-functional catalysis indicates that an organic p-n bilayer induces the catalytic oxidation involved in downhill reactions, not only under illumination but also in the dark. When the organo-bilayer is composed of a perylene derivative (3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI), n-type) and cobalt phthalocyanine (CoPc, p-type), only the photocatalytic oxidation of hydrazine (N2H4) occurs. However, the loading of Ag co-catalyst onto the CoPc surface in the PTCBI/CoPc bilayer successfully led to dual catalysis in terms of the oxidation of N2H4 to N2. To develop the present dual catalysis Ag loading was essential to achieve the catalysis performance particularly without irradiation.

Sustainable photoanode for water oxidation reactions: from metal-based to metal-free materials

Sunlight affords an inexhaustible and primary energy for Earth. A photoelectrochemical system can efficiently harvest solar energy and convert it into chemicals. However, sophisticated processes and expensive raw materials are...

Role of carbon quantum dots on Nickel titanate to promote water oxidation reaction under visible light illumination

Water oxidation reaction (WOR) is the heart for overall water splitting owing to its sluggish kinetics. Herein, carbon quantum dots (CQDs) are studied as co-catalyst to promote WOR by loading them on NiTiO₃ (NTO) photocatalyst. The performance can be obtained in a fold of 7 compared with pristine NTO in power-based photocatalytic system, and strong stability has received with preserving the output for at least 10 h. The CQDs have also demonstrated to load on NTO based photoanode for WOR, and a 6 times increasement has realized. In-situ characterizations have acquired to study the roles of CQDs for WOR and found that CQDs can facilitate the chemical adsorption of water molecules, and meanwhile promote the formation of hydroxyl radical as transition states of WOR. This demonstration presents a clue to understand the role of carbon in photocatalytic system to promote WOR and encourage its uses for advanced photoredox catalytic reactions.