Displaying publications 1 - 20 of 37 in total

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  1. Zeng D, Zhou T, Ong WJ, Wu M, Duan X, Xu W, et al.
    ACS Appl Mater Interfaces, 2019 Feb 13;11(6):5651-5660.
    PMID: 30615433 DOI: 10.1021/acsami.8b20958
    Sub-5 nm ultra-fine iron phosphide (FeP) nano-dots-modified porous graphitic carbon nitride (g-C3N4) heterojunction nanostructures are successfully prepared through the gas-phase phosphorization of Fe3O4/g-C3N4 nanocomposites. The incorporation of zero-dimensional (0D) ultra-small FeP nanodots co-catalysts not only effectively facilitate charge separation but also serve as reaction active sites for hydrogen (H2) evolution. Herein, the strongly coupled FeP/g-C3N4 hybrid systems are employed as precious-metal-free photocatalysts for H2 production under visible-light irradiation. The optimized FeP/g-C3N4 sample displays a maximum H2 evolution rate of 177.9 μmol h-1 g-1 with the apparent quantum yield of 1.57% at 420 nm. Furthermore, the mechanism of photocatalytic H2 evolution using 0D/2D FeP/g-C3N4 heterojunction interfaces is systematically corroborated by steady-state photoluminescence (PL), time-resolved PL spectroscopy, and photoelectrochemical results. Additionally, an increased donor density in FeP/g-C3N4 is evidenced from the Mott-Schottky analysis in comparison with that of parent g-C3N4, signifying the enhancement of electrical conductivity and charge transport owing to the emerging role of FeP. The density functional theory calculations reveal that the FeP/g-C3N4 hybrids could act as a promising catalyst for the H2 evolution reaction. Overall, this work not only paves a new path in the engineering of monodispersed FeP-decorated g-C3N4 0D/2D robust nanoarchitectures but also elucidates potential insights for the utilization of noble-metal-free FeP nanodots as remarkable co-catalysts for superior photocatalytic H2 evolution.
  2. Ong WJ, Tan LL, Chai SP, Yong ST, Mohamed AR
    Nanoscale, 2014 Feb 21;6(4):1946-2008.
    PMID: 24384624 DOI: 10.1039/c3nr04655a
    Titanium dioxide (TiO2) is one of the most widely investigated metal oxides due to its extraordinary surface, electronic and catalytic properties. However, the large band gap of TiO2 and massive recombination of photogenerated electron-hole pairs limit its photocatalytic and photovoltaic efficiency. Therefore, increasing research attention is now being directed towards engineering the surface structure of TiO2 at the most fundamental and atomic level namely morphological control of {001} facets in the range of microscale and nanoscale to fine-tune its physicochemical properties, which could ultimately lead to the optimization of its selectivity and reactivity. The synthesis of {001}-faceted TiO2 is currently one of the most active interdisciplinary research areas and demonstrations of catalytic enhancement are abundant. Modifications such as metal and non-metal doping have also been extensively studied to extend its band gap to the visible light region. This steady progress has demonstrated that TiO2-based composites with {001} facets are playing and will continue to play an indispensable role in the environmental remediation and in the search for clean and renewable energy technologies. This review encompasses the state-of-the-art research activities and latest advancements in the design of highly reactive {001} facet-dominated TiO2via various strategies, including hydrothermal/solvothermal, high temperature gas phase reactions and non-hydrolytic alcoholysis methods. The stabilization of {001} facets using fluorine-containing species and fluorine-free capping agents is also critically discussed in this review. To overcome the large band gap of TiO2 and rapid recombination of photogenerated charge carriers, modifications are carried out to manipulate its electronic band structure, including transition metal doping, noble metal doping, non-metal doping and incorporating graphene as a two-dimensional (2D) catalyst support. The advancements made in these aspects are thoroughly examined, with additional insights related to the charge transfer events for each strategy of the modified-TiO2 composites. Finally, we offer a summary and some invigorating perspectives on the major challenges and new research directions for future exploitation in this emerging frontier, which we hope will advance us to rationally harness the outstanding structural and electronic properties of {001} facets for various environmental and energy-related applications.
  3. Ong WJ, Tan LL, Chai SP, Yong ST, Mohamed AR
    ChemSusChem, 2014 Mar;7(3):690-719.
    PMID: 24532412 DOI: 10.1002/cssc.201300924
    Titanium dioxide (TiO2 ) is one of the most widely investigated metal oxides because of its extraordinary surface, electronic, and photocatalytic properties. However, the large band gap of TiO2 and the considerable recombination of photogenerated electron-hole pairs limit its photocatalytic efficiency. Therefore, research attention is being increasingly directed towards engineering the surface structure of TiO2 on the atomic level (namely morphological control of {001} facets on the micro- and nanoscale) to fine-tune its physicochemical properties; this could ultimately lead to the optimization of selectivity and reactivity. This Review encompasses the fundamental principles to enhance the photocatalytic activity by using highly reactive {001}-faceted TiO2 -based composites. The current progress of such composites, with particular emphasis on the photodegradation of pollutants and photocatalytic water splitting for hydrogen generation, is also discussed. The progresses made are thoroughly examined for achieving remarkable photocatalytic performances, with additional insights with regard to charge transfer. Finally, a summary and some perspectives on the challenges and new research directions for future exploitation in this emerging frontier are provided, which hopefully would allow for harnessing the outstanding structural and electronic properties of {001} facets for various energy- and environmental-related applications.
  4. Tong WL, Ong WJ, Chai SP, Tan MK, Hung YM
    Sci Rep, 2015;5:11896.
    PMID: 26100977 DOI: 10.1038/srep11896
    The unique characteristic of fast water permeation in laminated graphene oxide (GO) sheets has facilitated the development of ultrathin and ultrafast nanofiltration membranes. Here we report the application of fast water permeation property of immersed GO deposition for enhancing the performance of a GO/water nanofluid charged two-phase closed thermosyphon (TPCT). By benchmarking its performance against a silver oxide/water nanofluid charged TPCT, the enhancement of evaporation strength is found to be essentially attributed to the fast water permeation property of GO deposition instead of the enhanced surface wettability of the deposited layer. The expansion of interlayer distance between the graphitic planes of GO deposited layer enables intercalation of bilayer water for fast water permeation. The capillary force attributed to the frictionless interaction between the atomically smooth, hydrophobic carbon structures and the well-ordered hydrogen bonds of water molecules is sufficiently strong to overcome the gravitational force. As a result, a thin water film is formed on the GO deposited layers, inducing filmwise evaporation which is more effective than its interfacial counterpart, appreciably enhanced the overall performance of TPCT. This study paves the way for a promising start of employing the fast water permeation property of GO in thermal applications.
  5. Xu Q, Li W, Ding L, Yang W, Xiao H, Ong WJ
    Nanoscale, 2019 Jan 23;11(4):1475-1504.
    PMID: 30620019 DOI: 10.1039/c8nr08738e
    Metal-free carbonaceous nanomaterials have witnessed a renaissance of interest due to the surge in the realm of nanotechnology. Among myriads of carbon-based nanostructures with versatile dimensionality, one-dimensional (1D) carbon nanotubes (CNTs) and zero-dimensional (0D) carbon dots (CDs) have grown into a research frontier in the past few decades. With extraordinary mechanical, thermal, electrical and optical properties, CNTs are utilized in transparent displays, quantum wires, field emission transistors, aerospace materials, etc. Although CNTs possess diverse characteristics, their most attractive property is their unique photoluminescence. On the other hand, another growing family of carbonaceous nanomaterials, which is CDs, has drawn much research attention due to its cost-effectiveness, low toxicity, environmental friendliness, fluorescence, luminescence and simplicity to be synthesized and functionalized with surface passivation. Benefiting from these unprecedented properties, CDs have been widely employed in biosensing, bioimaging, nanomedicine, and catalysis. Herein, we have systematically presented the fascinating properties, preparation methods and multitudinous applications of CNTs and CDs (including graphene quantum dots). We will discuss how CNTs and CDs have emerged as auspicious nanomaterials for potential applications, especially in electronics, sensors, bioimaging, wearable devices, batteries, supercapacitors, catalysis and light-emitting diodes (LEDs). Last but not least, this review is concluded with a summary, outlook and invigorating perspectives for future research horizons in this emerging platform of carbonaceous nanomaterials.
  6. Chew KW, Chia SR, Chia WY, Cheah WY, Munawaroh HSH, Ong WJ
    Environ Pollut, 2021 Mar 01;278:116836.
    PMID: 33689952 DOI: 10.1016/j.envpol.2021.116836
    The remarkable journey of progression of mankind has created various impacts in the form of polluted environment, amassed heavy metals and depleting resources. This alarming situation demands sustainable energy resources and approaches to deal with these environmental hazards and power deficit. Pyrolysis and co-pyrolysis address both energy and environmental issues caused by civilization and industrialization. The processes use hazardous waste materials including waste tires, plastic and medical waste, and biomass waste such as livestock waste and agricultural waste as feedstock to produce gas, char and pyrolysis oil for energy production. Usage of hazardous materials as pyrolysis and co-pyrolysis feedstock reduces disposal of harmful substances into environment, reducing occurrence of soil and water pollution, and substituting the non-renewable feedstock, fossil fuels. As compared to combustion, pyrolysis and co-pyrolysis have less emission of air pollutants and act as alternative options to landfill disposal and incineration for hazardous materials and biomass waste. Hence, stabilizing heavy metals and solving the energy and waste management problems. This review discusses the pyrolysis and co-pyrolysis of biomass and harmful wastes to strive towards circular economy and eco-friendly, cleaner energy with minimum waste disposal, reducing negative impact on the planet and creating future possibilities.
  7. Samsudin MFR, Frebillot C, Kaddoury Y, Sufian S, Ong WJ
    J Environ Manage, 2020 Sep 15;270:110803.
    PMID: 32721291 DOI: 10.1016/j.jenvman.2020.110803
    To maximize the employment of sustainable solar energy in treating the recalcitrant pollutant and hydrogen energy production, the development of a highly efficient photocatalyst is desirable. Herein, a Z-scheme Ag/AgVO3/g-C3N4 photocatalyst was synthesized via a wet-impregnation method. The amount of Ag/AgVO3 deposited onto g-C3N4 has a significant effect on the photocharge carrier separation and migration of the as-developed Z-scheme photocatalyst. It was found that 0.5 wt % Ag/AgVO3/g-C3N4 photocatalyst exhibited a profound photocatalytic degradation performance with 82.6% ciprofloxacin removal and 3.57 mmol/h of hydrogen produced from natural rainwater under visible-light irradiation. Additionally, the apparent quantum efficiency (AQE) of this sample was 9.95% at 420 nm which is four times higher than the pure sample. The remarkable photocatalytic performance was attributed to the enhanced crystallographic structure, evidently from the XRD and XPS analysis. Moreover, the intimate contact between Ag/AgVO3 and g-C3N4 nanoparticles allows the smooth photocharge carrier separation and migrations, resulting in superior photocatalytic performance in comparison to the pure samples. Interestingly, the profound photocatalytic activity demonstrated here was achieved without the addition of any sacrificial reagents. This work demonstrates the feasibility of utilizing visible-light-driven photocatalysts in treating the recalcitrant antibiotic pollutants and producing hydrogen from natural rainwater.
  8. Putri LK, Ng BJ, Ong WJ, Lee HW, Chang WS, Chai SP
    ACS Appl Mater Interfaces, 2017 Feb 08;9(5):4558-4569.
    PMID: 28068056 DOI: 10.1021/acsami.6b12060
    Owing to its superior properties and versatility, graphene has been proliferating the energy research scene in the past decade. In this contribution, nitrogen (N-) and boron (B-) doped reduced graphene oxide (rGO) variants were investigated as a sole photocatalyst for the green production of H2 and their properties with respect to photocatalysis were elucidated for the first time. N- and B-rGOs were facilely prepared via the pyrolysis of graphene oxide with urea and boron anhydride as their respective dopant source. The pyrolysis temperature was varied (600-800 °C for N-rGO and 800-1000 °C for B-rGO) in order to modify dopant loading percentage (%) which was found to be influential to photocatalytic activity. N-rGO600 (8.26 N at%) and B-rGO1000 (3.59 B at%), which holds the highest at% from each of their party, exhibited the highest H2 activity. Additionally, the effects of the nature of N and B bonding configuration in H2 photoactivity were also examined. This study demonstrates the importance of dopant atoms in graphene, rendering doping as an effective strategy to bolster photocatalytic activity for standalone graphene derivative photocatalysts.
  9. Seng RX, Tan LL, Lee WPC, Ong WJ, Chai SP
    J Environ Manage, 2020 Feb 01;255:109936.
    PMID: 32063312 DOI: 10.1016/j.jenvman.2019.109936
    Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C3N4) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C3N4 to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C3N4 composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C3N4. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h+) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C3N4 photocatalyst systems for environmental remediation by utilising solar energy.
  10. Li M, Li W, Guan Q, Dai X, Lv J, Xia Z, et al.
    ACS Nano, 2021 12 28;15(12):19194-19201.
    PMID: 34797635 DOI: 10.1021/acsnano.1c03882
    Dry adhesives that combine strong adhesion, high transparency, and reusability are needed to support developments in emerging fields such as medical electrodes and the bonding of electronic optical devices. However, achieving all of these features in a single material remains challenging. Herein, we propose a pressure-responsive polyurethane (PU) adhesive inspired by the octopus sucker. This adhesive not only showcases reversible adhesion to both solid materials and biological tissues but also exhibits robust stability and high transparency (>90%). As the adhesive strength of the PU adhesive corresponds to the application force, adhesion could be adjusted by the preloading force and/or pressure. The adhesive exhibits high static adhesion (∼120 kPa) and 180° peeling force (∼500 N/m), which is far stronger than those of most existing artificial dry adhesives. Moreover, the adhesion strength is effectively maintained even after 100 bonding-peeling cycles. Because the adhesive tape relies on the combination of negative pressure and intermolecular forces, it overcomes the underlying problems caused by glue residue like that left by traditional glue tapes after removal. In addition, the PU adhesive also shows wet-cleaning performance; the contaminated tape can recover 90-95% of the lost adhesion strength after being cleaned with water. The results show that an adhesive with a microstructure designed to increase the contribution of negative pressure can combine high reversible adhesion and long fatigue life.
  11. Yu X, Ng SF, Putri LK, Tan LL, Mohamed AR, Ong WJ
    Small, 2021 12;17(48):e2006851.
    PMID: 33909946 DOI: 10.1002/smll.202006851
    Graphitic carbon nitride (g-C3 N4 ) is a kind of ideal metal-free photocatalysts for artificial photosynthesis. At present, pristine g-C3 N4 suffers from small specific surface area, poor light absorption at longer wavelengths, low charge migration rate, and a high recombination rate of photogenerated electron-hole pairs, which significantly limit its performance. Among a myriad of modification strategies, point-defect engineering, namely tunable vacancies and dopant introduction, is capable of harnessing the superb structural, textural, optical, and electronic properties of g-C3 N4 to acquire an ameliorated photocatalytic activity. In view of the burgeoning development in this pacey field, a timely review on the state-of-the-art advancement of point-defect engineering of g-C3 N4 is of vital significance to advance the solar energy conversion. Particularly, insights into the intriguing roles of point defects, the synthesis, characterizations, and the systematic control of point defects, as well as the versatile application of defective g-C3 N4 -based nanomaterials toward photocatalytic water splitting, carbon dioxide reduction and nitrogen fixation will be presented in detail. Lastly, this review will conclude with a balanced perspective on the technical and scientific hindrances and future prospects. Overall, it is envisioned that this review will open a new frontier to uncover novel functionalities of defective g-C3 N4 -based nanostructures in energy catalysis.
  12. Ong WJ, Tan LL, Ng YH, Yong ST, Chai SP
    Chem Rev, 2016 06 22;116(12):7159-329.
    PMID: 27199146 DOI: 10.1021/acs.chemrev.6b00075
    As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and "earth-abundant" nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The construction and characteristics of each classification of the heterojunction system will be critically reviewed, namely metal-g-C3N4, semiconductor-g-C3N4, isotype g-C3N4/g-C3N4, graphitic carbon-g-C3N4, conducting polymer-g-C3N4, sensitizer-g-C3N4, and multicomponent heterojunctions. The band structures, electronic properties, optical absorption, and interfacial charge transfer of g-C3N4-based heterostructured nanohybrids will also be theoretically discussed based on the first-principles density functional theory (DFT) calculations to provide insightful outlooks on the charge carrier dynamics. Apart from that, the advancement of the versatile photoredox applications toward artificial photosynthesis (water splitting and photofixation of CO2), environmental decontamination, and bacteria disinfection will be presented in detail. Last but not least, this comprehensive review will conclude with a summary and some invigorating perspectives on the challenges and future directions at the forefront of this research platform. It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g-C3N4-based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment.
  13. Li N, Yang Y, Shi Z, Lan Z, Arramel A, Zhang P, et al.
    iScience, 2022 Feb 18;25(2):103753.
    PMID: 35128355 DOI: 10.1016/j.isci.2022.103753
    Unique performance of the hybrid organic-inorganic halide perovskites (HOIPs) has attracted great attention because of their continuous exploration and breakthrough in a multitude of energy-related applications. However, the instability and lead-induced toxicity that arise in bulk perovskites are the two major challenges that impede their future commercialization process. To find a solution, a series of two-dimensional HOIPs (2D HOIPs) are investigated to prolong the device lifetime with highly efficient photoelectric conversion and energy storage. Herein, the recent advances of 2D HOIPs and their structural derivatives for the energy realms are summarized and discussed. The basic understanding of crystal structures, physicochemical properties, and growth mechanisms is presented. In addition, the current challenges and future directions to provide a roadmap for the development of next generation 2D HOIPs are prospected.
  14. Phang SJ, Goh JM, Tan LL, Lee WPC, Ong WJ, Chai SP
    Environ Sci Pollut Res Int, 2021 Jan;28(4):4388-4403.
    PMID: 32940840 DOI: 10.1007/s11356-020-10814-z
    Graphitic carbon nitride (g-C3N4) has been regarded as a promising visible light-driven photocatalyst ascribable to its tailorable structures, thermal stability and chemical inertness. Enhanced photocatalytic activity is achievable by the construction of homojunction nanocomposites to reduce the undesired recombination of photogenerated charge carriers. In the present work, a novel g-C3N4/g-C3N4 metal-free homojunction photocatalyst was synthesized via hydrothermal polymerization. The g-C3N4/g-C3N4 derived from urea and thiourea demonstrated admirable photocatalytic activity towards rhodamine B (RhB) degradation upon irradiation of an 18 W LED light. The viability of the photoreaction with a low-powered excitation source highlighted the economic and environmental benefits of the process. The optimal g-C3N4/g-C3N4 homojunction photocatalyst exhibited a 2- and 1.8-fold increase in efficiency in relative to pristine g-C3N4 derived from urea and thiourea respectively. The enhanced photocatalytic performance is credited to the improved interfacial transfer and separation of electron-hole pairs across the homojunction interface. Furthermore, an excellent photochemical stability and durability is displayed by g-C3N4/g-C3N4 after three consecutive cycles. In addition, a plausible photocatalytic mechanism was proposed based on various scavenging tests. Overall, experimental results generated from this study is expected to intrigue novel research inspirations in developing metal-free homojunction photocatalysts to be feasible for large-scale wastewater treatment without compromising economically. Graphical abstract.
  15. Show PL, Chew KW, Ong WJ, Varjani S, Juan JC
    Beilstein J Nanotechnol, 2023;14:377-379.
    PMID: 37025364 DOI: 10.3762/bjnano.14.32
  16. Tan XQ, Mo W, Lin X, Loh JY, Mohamed AR, Ong WJ
    Nanoscale, 2023 Apr 06;15(14):6536-6562.
    PMID: 36942445 DOI: 10.1039/d2nr05718b
    The electro/photocatalytic CO2 reduction reaction (CO2RR) is a long-term avenue toward synthesizing renewable fuels and value-added chemicals, as well as addressing the global energy crisis and environmental challenges. As a result, current research studies have focused on investigating new materials and implementing numerous fabrication approaches to increase the catalytic performances of electro/photocatalysts toward the CO2RR. MXenes, also known as 2D transition metal carbides, nitrides, and carbonitrides, are intriguing materials with outstanding traits. Since their discovery in 2011, there has been a flurry of interest in MXenes in electrocatalysis and photocatalysis, owing to their several benefits, including high mechanical strength, tunable structure, surface functionality, high specific surface area, and remarkable electrical conductivity. Herein, this review serves as a milestone for the most recent development of MXene-based catalysts for the electrocatalytic and photocatalytic CO2RR. The overall structure of MXenes is described, followed by a summary of several synthesis pathways classified as top-down and bottom-up approaches, including HF-etching, in situ HF-formation, electrochemical etching, and halogen etching. Additionally, the state-of-the-art development in the field of both the electrocatalytic and photocatalytic CO2RR is systematically reviewed. Surface termination modulation and heterostructure engineering of MXene-based electro/photocatalysts, and insights into the reaction mechanism for the comprehension of the structure-performance relationship from the CO2RR via density functional theory (DFT) have been underlined toward activity enhancement. Finally, imperative issues together with future perspectives associated with MXene-based electro/photocatalysts are proposed.
  17. Tan XQ, Zhang P, Chen B, Mohamed AR, Ong WJ
    J Colloid Interface Sci, 2024 Feb 09;662:870-882.
    PMID: 38382371 DOI: 10.1016/j.jcis.2024.02.027
    The extensive examination of hexagonal molybdenum carbide (β-Mo2C) as a non-noble cocatalyst in the realm of photocatalytic H2 evolution is predominantly motivated by its exceptional capacity to adsorb H+ ions akin to Pt and its advantageous conductivity characteristics. However, the H2 evolution rate of photocatalysts modified with β-Mo2C is limited as a result of their comparatively low ability to release H through desorption. Therefore, a facile method was employed to synthesize carbon intercalated dual phase molybdenum carbide (MC@C) quantum dots (ca. 3.13 nm) containing both α-MoC and β-Mo2C decorated on g-C3N4 (gCN). The synthesis process involved a simple and efficient combination of sonication-assisted self-assembly and calcination techniques. 3-MC@C/gCN exhibited the highest efficiency in generating H2, with a rate of 4078 µmol g-1h-1 under 4 h simulated sunlight irradiation, which is 13 times higher than pristine gCN. Furthermore, from the cycle test, 3-MC@C/gCN showcased exceptional photochemical stability of 65 h, as it maintained a H2 evolution rate of 40 mmol g-1h-1. The heightened level of activity observed in the 3-MC@C/gCN system can be ascribed to the synergistic effects of MoC-Mo2C that arise due to the existence of a carbon layer. The presence of a carbon layer enhanced the transmission of photoinduced electrons, while the MoC-Mo2C@C composite served as active sites, thereby facilitating the H2 production reaction of gCN. The present study introduces a potentially paradigm-shifting concept pertaining to the exploration of novel Mo-based cocatalysts with the aim of augmenting the efficacy of photocatalytic H2 production.
  18. Ong WJ, Tan LL, Chai SP, Yong ST
    Dalton Trans, 2015 Jan 21;44(3):1249-57.
    PMID: 25415620 DOI: 10.1039/c4dt02940b
    In this paper, noble-metal Pt nanoparticles of around 2.5 nm were deposited on graphitic carbon nitride (g-C3N4) synthesized by a chemical reduction process in ethylene glycol. Compared with pure g-C3N4, the resulting Pt-loaded g-C3N4 (Pt/CN) exhibited a considerable improvement in the photoreduction of CO2 to CH4 in the presence of water vapor at ambient temperature and atmospheric pressure under visible light irradiation. 2 wt% Pt-loaded g-C3N4 (2Pt/CN) nanocomposites produced the highest CH4 yield of 13.02 μmol gcatalyst(-1) after 10 h of light irradiation, which was a 5.1-fold enhancement in comparison with pure g-C3N4 (2.55 μmol gcatalyst(-1)). The remarkable photocatalytic activity of Pt/CN nanostructures in the CH4 production was ascribed to the enhanced visible light absorption and efficient interfacial transfer of photogenerated electrons from g-C3N4 to Pt due to the lower Fermi level of Pt in the Pt/CN hybrid heterojunctions as evidenced by the UV-Vis and photoluminescence studies. The enriched electron density on Pt favored the reduction of CO2 to CH4via a multi-electron transfer process. This resulted in the inhibition of electron-hole pair recombination for effective spatial charge separation, thus enhancing the photocatalytic reactions. Based on the experimental results obtained, a plausible mechanism for improved photocatalytic performance associated with Pt/CN was proposed.
  19. Ong WJ, Tan LL, Chai SP, Yong ST
    Chem Commun (Camb), 2015 Jan 18;51(5):858-61.
    PMID: 25429376 DOI: 10.1039/c4cc08996k
    A facile one-pot impregnation-thermal reduction strategy was employed to fabricate sandwich-like graphene-g-C3N4 (GCN) nanocomposites using urea and graphene oxide as precursors. The GCN sample exhibited a slight red shift of the absorption band edge attributed to the formation of a C-O-C bond as a covalent cross linker between graphene and g-C3N4. The GCN sample demonstrated high visible-light photoactivity towards CO2 reduction under ambient conditions, exhibiting a 2.3-fold enhancement over pure g-C3N4. This was ascribed to the inhibition of electron-hole pair recombination by graphene, which increased the charge transfer.
  20. Tan LL, Ong WJ, Chai SP, Mohamed AR
    Chem Commun (Camb), 2014 Jul 4;50(52):6923-6.
    PMID: 24841282 DOI: 10.1039/c4cc01304b
    A facile and dopant-free strategy was employed to fabricate oxygen-rich TiO2 (O2-TiO2) with enhanced visible light photoactivity. Such properties were achieved by the in situ generation of oxygen through the thermal decomposition of the peroxo-titania complex. The O2-TiO2 photocatalyst exhibited high photoactivity towards CO2 reduction under visible light.
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