Synergized Mechanistic and Solar Photocatalysis Features of N-TiO2 Functionalised Activated Carbon

A TiO2 photocatalysts was successfully functionalised by employing nitrogen (N) as a dopant on activated carbon (AC) support as synergist. Two different types of activated carbon adopting namely Garcinia mangostana and palm shell as precursor were chosen as an activated carbon support. Thus the synthesized samples were examined for its physical and chemistry properties through advanced microscopic and spectroscopic techniques. The results revealed the contribution of adsorbent support through the rich surface area while doping of nitrogen contributed for effectively utilizing the incident photons by narrowing the band gap energy. The synergetic adsorption-photocatalytic activity was investigated by adopting batik dye, Remazol Brilliant Blue Dye (RBB) as model pollutant. Thus the N-TiO2 functionalised activated carbon demonstrated excellent adsorption-photocatalytic activity with 80% removal efficiency in 6 h. The synergism of adsorption photocatalysis portrayed the alternative for treating recalcitrant RBB a predominant dye found in batik textile industry wastewate

Metal free and sunlight driven g-C3N4 based photocatalyst using carbon quantum dots from Arabian dates: Green strategy for photodegradation of 2,4-dichlorophenol and selective detection of Fe3+

The fabrication of photocatalyst with a visible response and prolonged lifetime of charge carriers is a significant tactic to treat EDCs. In this work, a green synthesis route was adopted to prepare carbon quantum dots (CQDs) from Arabian dates (AD-CQDs) via hydrothermal method. The different weight percentages of fabricated AD-CQDs (10, 15 and 20 wt%) were coupled with graphitic carbon nitride (g-C3N4) to construct AD-CQDs/g-C3N4 composites to degrade 2,4-dicholorophenol (2,4-DCP) under sunlight irradiation with an average light intensity of ~973 × 100 lx. The obtained AD-CQDs were used as a highly selective sensor for ferric (Fe3+) ions, with a low detection limit of 1 nM. The increase loading of AD-CQDs resulted in particle agglomeration which decreased the specific surface area of g-C3N4 from 74.799 m2/g to 62.542 m2/g. The low specific surface area in the composites did not hamper the photocatalytic performance in which all composites showed a higher degradation rate than that of g-C3N4. With the optimum loading of AD-CQDs (20 wt%), the composite degraded 100% of 2,4-DCP in 90 min which was 1.7 times higher than g-C3N4 (59.48%). The excellent photocatalytic performance was mainly correlated to the effective separation of photogenerated electrons as evidenced by TRPL and transient photocurrent response. The second factor is visible light response because of the minor decrease of band gap energy as evidenced in UV–vis DRS spectra. Both factors are attributed to the dual functions of AD-CQDs as electron acceptors and photosensitizers. The simple and low-cost synthesis strategy could be an alternative to obtain sunlight driven photocatalysts without coupling with metal dopants or other semiconductors

Integrated adsorption-photocatalytic degradation of chicken processing wastewater using powdered activated carbon-supported graphitic carbon nitride

Due to the expansion of agricultural sector, a massive volume of chicken processing wastewater has been produced and the conventional technologies are ineffective to remove organic and inorganic compounds. Thus, this work investigates the performance for the adsorption-photocatalytic degradation of chicken processing wastewater using powdered activated carbon (AC) supported on different weightage of graphitic carbon nitride (g-C3N4) (20 wt%, 40 wt% and 60 wt%). The AC was successfully combined with g-C3N4 by pyrolyzing the urea and AC mixture. The presence of AC reduced the agglomeration of g-C3N4 by providing a larger surface area to trigger more active sites. AC achieved the highest chemical oxygen demand (COD) adsorption efficiency (79.00 %) whereas the pure g-C3N4 showed the strongest adsorption capacity for orthophosphate (49.10 %) and ammonia nitrogen (NH3-N) (100 %). This proves that the microporous structure of AC was not suitable to remove orthophosphate and NH3-N. The highest photodegradation efficiency of COD (47.00 %), orthophosphate (49.00 %) and NH3-N (52.90 %) was successfully achieved by 20 wt% g-C3N4/AC, g-C3N4 and 60 wt% g-C3N4/AC, respectively. Overall, 98.20 % of COD, 98.10 % of orthophosphate and 100% of NH3-N was removed using integrated adsorption-photocatalytic degradation, making this technique a feasible method for on-site chicken processing wastewater treatment

Nanocrystal TiO2 Engulfed SiO2-Barium Hexaferrite for Enhanced Electrons Mobility and Solar Harvesting Potential

Barium hexaferrite embedded-silica-titania photocatalyst (TiO2-SiO2-BaFe12O19) was synthesized through sol-gel, liquid catalytic phase transformation and solid reaction routes. The magnetic photocatalyst was aimed to harvest the photoenergy from the sunlight, minimize the electron-holes recombination rate, improve the long lifetime charge-carriers transfer to maximize the photocatalytic activity and enhances the separation and reusability of it. The as-synthesized photocatalyst was characterized and the photocatalytic activity was evaluated for the reduction of 2, 4-dichlorophenol (2, 4-DCP) under direct sunlight. The presence of SiO2 interlayer in TiO2-SiO2-BaFe12O19 prevents the phase transformation of magnetic core. TiO2-SiO2-BaFe12O19 benefits the magnetic separation with appreciable magnitude of coercivity (5035.6 Oe) and saturation magnetization (18.8256E-3 emu/g), respectively. The ferrite ions from the magnetic core which dispersed into TiO2 matrix exhibited an evident shift of the absorption in the visible region. This was again confirmed with the reduced band gap energy of 1.90 eV. Furthermore, TiO2-SiO2-BaFe12O19 destructed 100% of 2, 4-DCP compound within 150 min under very bright sunlight with an average irradiance of 820.8 W/m2 (results not shown). The embedding of BaFe12O19 with a SiO2 layer onto TiO2 nanocrystals contributed for an excellent solar-light utilization and ease magnetic separation of the nanosized photocatalyst

Dopant-free Oxygen-rich Titanium Dioxide: LED Light-induced Photocatalysis and Mechanism Insight

In this work, we successfully synthesized visible light-responsive oxygen-rich titanium dioxide (O2–TiO2) photocatalysts. Through hydrothermal decomposition of peroxo-titania complex, the in situ generation of oxygen significantly shifted the light absorption toward visible region. The existence and contribution of oxygen excess defect present in O2–TiO2 was confirmed through FTIR and XPS analysis. The annealing temperature influenced the oxygen content and textural property of O2–TiO2 samples and subsequently their photocatalytic activity. The O2–TiO2 calcined at optimum temperature of 300 °C recorded the highest photocatalytic activity toward methylene blue degradation, approximately 7.3- and 3.2-fold higher than that of commercial P25 and anatase TiO2, respectively. The enhancement was attributed to shortening of band gap and low recombination rate of charge carriers when the oxygen content increased at higher temperature. In addition, O2–TiO2 displayed high reusability rate and good catalytic stability after being evaluated by four consecutive catalytic runs. The reactive radical species responsible for charge transfer mechanism and high photocatalytic activity were hydroxyl radical (·OH), holes and superoxide radical anions (·O2−) after performing multiple scavenging tests

Amalgamation of N-graphene quantum dots with nanocubic like TiO2: An insight study of sunlight sensitive photocatalysis

In this work, a sunlight-sensitive photocatalyst of nanocubic-like titanium dioxide (TiO2) and N-doped graphene quantum dots (N-GQDs) is developed through a simple hydrothermal and physical mixing method. The successful amalgamation composite photocatalyst characteristics were comprehensively scrutinized through various physical and chemical analyses. A complete removal of bisphenol A (BPA) is attained by a synthesized composite after 30 min of sunlight irradiation as compared to pure TiO2. This clearly proved the unique contribution of N-GQDs that enhanced the ability of light harvesting especially under visible light and near-infrared region. This superior characteristic enables it to maximize the absorbance in the entire solar spectrum. However, the increase of N-GQDs weight percentage has created massive oxygen vacancies that suppress the generation of active radicals. This resulted in a longer duration for a complete removal of BPA as compared to lower weight percentage of N-GQDs. Hence, this finding can offer a new insight in developing effective sunlight-sensitive photocatalysts for various complex organic pollutants degradation

Mechanistic Insights Into Plasmonic Photocatalysts in Utilizing Visible Light

The utilisation of sunlight as an abundant and renewable resource has motivated the development of sustainable photocatalysts that can collectively harvest visible light. However, the bottleneck in utilising the low energy photons has led to the discovery of plasmonic photocatalysts. The presence of noble metal on the plasmonic photocatalyst enables the harvesting of visible light through the unique characteristic features of the noble metal nanomaterials. Moreover, the formation of interfaces between noble metal particles and semiconductor materials further results in the formation of a Schottky junction. Thereby, the plasmonic characteristics have opened up a new direction in promoting an alternative path that can be of value to the society through sustainable development derived through energy available for all for diverse applications. We have comprehensively prepared this review to specifically focus on fundamental insights into plasmonic photocatalysts, various synthesis routes, together with their strengths and weaknesses, and the interaction of the plasmonic photocatalyst with pollutants as well as the role of active radical generation and identification. The review ends with a pinnacle insight into future perspectives regarding realistic applications of plasmonic photocatalysts

Preparation of Improved p-n Junction NiO/TiO2 Nanotubes for Solar-Energy-Driven Light Photocatalysis

Self-organized TiO2 nanotubes (TNTs) with average inner diameter of 109 nm, wall thickness of 15 nm, and tube length of 7–10 μm were loaded with nickel oxide (NiO) nanoparticles via incipient wet impregnation method. The molar concentration of Ni(NO3)2·6H2O aqueous solution varied in a range of 0.5 M–2.5 M. The samples were characterized for crystalline phase, morphology, topography, chemical composition, Raman shift, and UV-Vis diffusion reflection properties. The finding shows that the loading of NiO did not influence the morphology, structure, and crystalline phase of TNTs but it exhibited significant effect on crystallite size and optical absorption properties. Further, the solar-energy-driven the photocatalytic activity of NiO/TNTs and pure TNTs was evaluated by degrading methylene blue (MB). The results confirm that photocatalytic efficiency of NiO/TNTs is higher than that of TNTs

Bioinspired Synthesis of Carbon Dots/g-C

This study reports a fast and green preparative strategy to synthesize water soluble and fluorescent carbon quantum dots (CQDs) through hydrothermal method by using low cost organic waste of human fingernails as the carbon precursor for the first time. The coupling of CQD with pure carbon nitride (g-C3N4) was further explored to enhance the latter’s performance in photocatalysis of 2,4-dicholorophenol (2,4-DCP), a toxic and recalcitrant compound mostly released from industrial effluent. Such coupling overcame the weakness of pure g-C3N4 in photocatalysis process by broadening its visible light absorption and promoting the charge separation. As a result, the removal rate of CQD/ g-C3N4(10) was up to 71.53%, which was approximately 1.5 times higher than that of pure g-C3N4 under sunlight irradiation. The morphological structure, optical properties and chemical compositions of CQDs/g-C3N4 composites were characterized using various spectroscopic techniques including field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray (EDX) and Ultraviolet-visible diffuse reflectance spectra (UV-DRS)