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"ABSTRACTThe purpose of this study is to develop a low cost, easy prepared, and environmentally friendly photocatalyst to produce hydrogen from aqueous methanol solution by combining catalytic reforming (metal based catalyst) and photocatalytic process (semiconductor based photocatalyst), at ambient condition under photon exposure. The effect of impregnated Cu and Ni (which are proven catalysts for thermal reforming) to TiO2 were investigated as well as the role/significance and behavior of methanol and water in photo-reforming process. As prepared Cu/TiO2 and Ni/TiO2 photocatalyst were characterized by ICP-AES, XRD, SEM, TEM, and UV-Vis DRS for better understanding of the photocatalytic reforming behavior. The optimum loadings of Cu and Ni into TiO2 surface were found to be 3% and 1% respectively. H2 generated from photoreforming of aqueous methanol solution (80% methanol v/v) over 3% Cu/TiO2 UV illumination was 4464.3 μmol.gcat 1.h-1, 5.5 times higher than unloaded TiO2 (803 μmol.gcat-1.h-1) while H2 yield over Ni/TiO2 wasfound to be 5200 μmol.gcat-1.h-1, 6.5 times higher compared to unloaded TiO2. In term of stability, Ni/TiO2 also shows superior performance compared to Cu/TiO2 and unloaded TiO2. Ni/TiO2 can still obtain final rate of 66% of its initial rate while only 42.4% was obtained for the case of Cu/TiO2, yet it is still slightly better than unloaded TiO2 (40.8%). Ni/TiO2 superiority in photocatalytic performance over Cu/TiO2 may be attributed to its higher work function which leads to higher electron trapping ability, better electron transfer from conduction band of TiO2 to metal site, and lower hydrogen overpotential. In order to investigate the role and significance of methanol and water on aqueous methanol photocatalytic reforming system, the methanol-water composition was varied during this particular study. The rates of hydrogen evolution displayed bell-shaped curves as a function of methanol volume fraction in the solution. The optimum hydrogen evolution rate was achieved in methanol volumetric ratio of 60-80%, in agreement with stoichiometric value of methanol:water mixture (1:1 molar ratio or 0.69:0.31 volumetric ratio). Both methanol and water show typical Freundlich adsorption behaviors. For solution containing 0-70% methanol, relationship between the hydrogen generation rate (v) and methanol content ([M]) is represented as v = 637.15[M]0.439. For solution containing 0-30% water, relationship between the hydrogen generation rate (v) and water content ([W]) is represented as v = 2594.1[W]0.161. This indicates that adsorption of water and methanol on the photocatalyst was a crucial part of the reaction mechanism."

"Modifications of the TiO2 P25 photocatalyst with metals: Platinum (Pt), Copper (Cu) and non-metal: Nitrogen (N) doping to produce Hydrogen (H2) from a glycerol-water mixture have been investigated. The metals (Pt and Cu) were loaded into Titanium Dioxide (TiO2 ) surface by employing an impregnation and Photo-Assisted Deposition (PAD) method, respectively. As prepared the metal doped TiO2 photocatalyst was then dispersed into an ammonia solution to obtain N-doped photocatalysts. The modified photocatalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS). XRD patterns indicated that the modified TiO2 photocatalysts have a nano-size crystallite range of 16-23 nm, while the DRS analysis showed that the doping of both metal and non-metal into TiO2 photocatalysts could effectively shift photon absorption to the visible light region. The optimum Cu loading of Cu-N-TiO2 was found to be 5%, resulting in a 10 times higher H2 production improvement level when compared to unloaded TiO2, even though this is still considered to be inferior compared to that of a 1% Pt loading, which results in a 34 times higher level than an unmodified TiO2photocatalyst. The effect of glycerol concentrations on hydrogen production has also been studied. This method offers a promising technology to find renewable and clean energy by using cheap materials and a simple technology."

"ABSTRAKUpaya untuk memproduksi hidrogen masih sedikit dari sumber yang terbarukan, termasuk hasil limbah biomassa berupa gliserol. Kombinasi proses fotokatalisis dan reformasi uap untuk produksi hidrogen telah diinvestigasi. Analisis SEM menunjukkan morfologi batu apung yang di-coating dengan TiO2 dan TiO2-Ni menempel pada batu apung secara merata. Analisis UV-Vis DRS menunjukkan batu apung yang di-coating TiO2 dan TiO2-Ni memiliki absorbansi dengan band gap energy yaitu menjadi 3,1 eV untuk batu apung-TiO2 dan 3 eV untuk batu apung-TiO2-Ni sehingga menunjukkan adanya penurunan energy bandgap. Penambahan dopan Ni pada TiO2 mampu menaikkan produksi hidrogen mencapai 1,5 kali lebih banyak dibandingkan hanya dengan TiO2. Melalui proses fotokatalisis selama 250 menit dengan mengkombinasikan proses fotokatalisis dan reformasi uap pada suhu 100 0C menghasilkan hidrogen sebesar 2334 µmol.

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ABSTRACT

Attempts to produce hydrogen is still slightly from renewable sources, including biomass waste results in the form of glycerol. The combination process of photocatalytic and steam reforming for hydrogen production has been investigated. SEM analysis showed that the morphology of pumice-coating with TiO2 and TiO2-Ni stuck in pumice evenly. UV-Vis DRS analysis shows that in the pumice-coating of TiO2 and TiO2-Ni has absorbance with a band gap energy is 3.1 eV for pumice-TiO2 and 3 eV for pumice-TiO2-Ni suggesting a decrease in the bandgap energy . The addition of dopants Ni on TiO2 is able to increase the production of hydrogen up to 1.5 times more than the just the TiO2. Through a photocatalytic process for 250 minutes by combining the photocatalytic process and steam reforming at 100 0C produces hydrogen at 2334 μmol."

"Optimasi berbagai parameter untuk preparasi fotokatalis TiO2 nanotubes dan TiO2 nanowires telah dilakukan, diantaranya dengan kombinasi proses sonikasi dan hidrotermal yang dilanjutkan dengan post treatment (kalsinasi atau hydrothermal post treatment) dan penambahan dopan logam (Cu, Pt) dan dopan nonlogam (N). Karakterisasi terhadap hasil sintesis dilakukan dengan menggunakan analisa TEM, SEM, BET, DRS dan XRD. Dari hasil analisa TEM dan SEM menunjukkan proses kombinasi sonikasi hidrothermal menggunakan NaOH diperoleh morfologi nanotubes dengan diameter luar 40 nm, sedangkan dengan KOH diperoleh struktur nanowires dengan diameter luar sebesar 6 nm. Hasil pengujian XRD menunjukkan fasa kristal baik untuk nanotubes maupun nanowires yang dihasilkan adalah anatase. Uji aktifitas katalis untuk produksi hidrogen menggunakan sacrificial agent metanol.Dari hasil pengujian menunjukkan modifikasi TiO2 dari nanopartikel menjadi nanotubes dapat meningkatkan produksi hidrogen menjadi dua sampai tiga kalinya, sedangkan modifikasi ke bentuk nanowires menjadi dua kali dibandingkan TiO2 P25. Luas permukaan yang tinggi dan morfologi berongga pada nanotubes menyebabkan dispersi dopan Pt pada TiO2 nanotubes menjadi lebih baik sehingga mampu meningkatkan aktivitas fotokatalis dalam memproduksi hidrogen dari air hingga delapan belas kali lebih tinggi dibandingkan tanpa dopan platina. Pemberian dopan nitrogen pada fotokatalis TiO2 nanotube belum mampu menggeser panjang gelombang absorbansi secara signifikan sehingga dengan sumber foton sinar tampak belum dapat menghasilkan hidrogen yang cukup tinggi.

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Optimization of various parameters on the preparation of TiO2 nanotubes and TiO2 nanowires have been conducted, such as combination of sonication and hydrothermal process followed by post-treatment (calcination or hydrothermal post treatment) and the addition of dopant metal (Cu, Pt) and non-metallic dopants (N). The modified catalysts were characterized using TEM, SEM, BET, DRS and XRD. The TEM and SEM analysis showed that the sonication-hydrothermal treatment with aqueous NaOH and KOH lead to the formation of nanotubes and nanowires morphology with an average outer diameter of 40 nm and 6 nm, respectively. XRD analysis showed that the both morphologies have anatase crystalline phase. Performance of the prepared photocatalyst on hydrogen production was examined by using methanol as sacrificial agent.The results indicated the modification of TiO2 nanoparticles into nanotubes could increased in producing hydrogen two-three fold, while the modification to the nanowires into two fold comparing to that of unmodified TiO2 (P25). Larger surface area and porous morphology in nanotubes enhanced the Pt dopant dispersion on TiO2 NT to increase the photocatalyst activity. Furthermore, this increased the production of hydrogen by 18 fold compared to that of non doped TiO2 nanotubes. However introduction of N dopant to the TiO2 nanotubes was not able to shift the absorbtion band toward visible region. Therefore, the high yield of hydrogen production was not achieved by as prepared N doped TiO2, when visible light was used as the photon source."

"Upaya untuk memproduksi hidrogen masih sedikit dari sumber yang terbarukan. TiO2 dalam bentuk nanotube arrays dengan dopan Boron yang disintesis dengan metode anodisasi untuk produksi hidrogen telah diinvestigasi. Perlakuan termal katalis B-TiO2 nanotube arrays (B-TNTAs) dilakukan dengan kalsinasi reduksi dengan gas hidrogen pada suhu 500oC selama 2 jam. Analisis SEM menunjukkan morfologi nanotube arrays tiap konsentrasi boron seragam. Analisis UV-Vis DRS menunjukkan B-TNTAs memiliki absorbansi yang besar pada jangkauan panjang gelombang sinar tampak dengan band gap energy yang relatif rendah yaitu menjadi 2,9 eV. Analisis XRD menunjukkan hasil 100% kristal anatase murni. Melalui proses fotokatalisis, hidrogen mampu dihasilkan hingga 48959 μmol/m2 setelah 4 jam pengujian dengan katalis 7,5 mM B-TNTAs.

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Attempts to produce hydrogen is still slightly from renewable sources. TiO2 nanotube arrays in the form of boron dopants synthesized by anodizing method for hydrogen production has been investigated. Catalyst-thermal treatment of TiO2 nanotube arrays B (B-TNTAs) performed by calcination reduction with hydrogen gas at a temperature of 500oC for 2 hours. SEM analysis showed the morphology of nanotube arrays by uniform boron concentration. UV-Vis DRS analysis showed B-TNTAs has a large absorbance in the visible wavelength range with a band gap energy is relatively low, to 2.9 eV. XRD analysis produces 100% anatase crystals. Through a photocatalytic process, hydrogen is able to produce up to 48959 μmol/m2 after 4 hours of testing with catalyst 7.5 mM B-TNTAs."

"Produksi hidrogen dengan menggunakan metanol atau gliserol sebagai elektron donor pada fotokatalis TiO2, TiNT, Pt/TiO2 dan Pt/TiNT pada suhu reaksi dari 30 oC sampai dengan 70 oC telah diteliti. Metanol dan gliserol efektif sebagai elektron donor untuk produksi hidrogen secara fotokatalisis. Penggunaan metanol lebih unggul 10% dari gliserol pada semua katalis dalam total produksi hidrogen. Produksi hidrogen terbaik ditunjukkan oleh fotokatalis Pt(1%)/TiNT dengan metanol sebagai elektron donor, yaitu sebesar 2306 µmol/gcat, sementara total hidrogen dengan gliserol sebesar 2120 µmol/gcat. Penggunaan dopan Pt pada fotokatalis menghasilkan produksi hidrogen dua kali lebih besar dibandingkan dengan tanpa dopan.

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Hidrogen production with methanol or glycerol as sacrificial agent using TiO2, TiO2 Nanotubes, Pt/TiO2 and Pt/TiO2 Nanotubes photocatalysts at reaction temperature 30 oC to 70 oC have been investigated. Methanol and glycerol were effective for hydrogen production and the best result was methanol with Pt(1%)/TiO2 that have 2306 µmol/gcat, meanwhile with glycerol only produce 2120 µmol/gcat. The other photocatalyst also have the same pattern, which metanol give 10% higher result on total hydrogen production. Catalyst with Pt give twice higher hydrogen production rather than with no Pt."

"In the plasma electrolysis process, hydrogen generation around the cathode is affected by the amount of evaporation energy. Utilizing a veil, minimizing the cooling in the liquid phase, and maximizing the cooling in the gas phase become important parameters to improve the process efficiency of hydrogen production. This research aims to obtain an optimum high-efficiency electrolysis plasma reactor based on decreased energy consumption and increased hydrogen gas production. The research method varied the NaOH concentration, voltage, veil length, cathode depth, and the volume of the methanol additive. In characterizing the current and voltage, as the concentration increases, the voltage needed to form the plasma will decrease. As the concentration and voltage increase, the rate of production, hydrogen content percentage, and the hydrogen ratio also increase, while the energy consumption decreases. The optimum condition, based on variations of veil length, is 5 cm when the depth of the cathode is 1 cm below the surface of the solution. Improving the efficiency of the hydrogen production process can be done by adding methanol. The best result was achieved using 15% volumes of methanol additive in 0.01 M NaOH, and higher hydrogen-ratio plasma-electrolysis results were found in comparison with Faraday electrolysis: the hydrogen ratio was 151.88 mol/mol, the lowest energy consumption was 0.89 kJ/mmol, and the highest hydrogen production rate was 31.45 mmol/min. The results show that this method can produce hydrogen 152 times more than Faraday electrolysis."

"ABSTRAKGas hidrogen banyak diperoleh dari proses elektrolisis yang memerlukan energi listrikyang besar. Elektrolisis plasma adalah teknologi baru dalam meningkatkan produktifitashidrogen sekaligus menekan kebutuhan listrik. Penelitian ini dilakukan untuk mengujiefektivitas proses elektrolisis plasma dengan penambahan aditif (larutan metanol danetanol) yang dinyatakan sebagai jumlah produk hidrogen per satuan energi listrik yangdikonsumsi dengan memvariasikan temperatur, tegangan listrik dan konsentrasi larutanKOH. Efektivitas proses ini dibandingkan dengan efektivitas elektrolisis Faraday danelektrolisis plasma tanpa penambahan aditif. Hasil percobaan menunjukkan kenaikankonsentrasi KOH dan tegangan listrik menyebabkan kenaikan jumlah produk hidrogen.Proses elektrolisis plasma pada penelitian ini dapat meningkatkan efektivitas proseshingga 5 kali lipat lebih tinggi dibandingkan dengan elektrolisis plasma tanpapenambahan aditif.

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ABSTRACTHydrogen is commonly produced by electrolysis which consumes a great deal of energy.Plasma electrolysis is a new technology that can increases hydrogen productivity whilelowering electrical energy needs. This research aimed to test the effectiveness of theplasma electrolysis process with methanol and ethanol addition which is expressed as thenumber of products of hydrogen per unit of electrical energy consumed by investigatedtemperature, electrical voltage and the concentration of KOH solution. Then, theeffectiveness of this process compared with the effectiveness of electrolysis Faraday.Results showed an increase of KOH concentration and the voltage causes an increase inthe hydrogen product. Plasma electrolysis process in this research can improve theeffectiveness of processes to 5 fold higher compared plasma electrolysis withoutmethanol and ethanol addition."

"Titania nanotubes (TiO2 NT) and Titania nanowires (TiO2 NW) were fabricated using TiO2 Degussa P25 (TiO2 P25) nanoparticle as precursors via a sonication-hydrothermal combination approach. The prepared catalysts were characterized by means of an X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet-visible diffuse reflectance spectroscopy (DRS) and the Brunauer-Emmett-Teller technique (BET). The photocatalytic activity of prepared catalysts was evaluated for photocatalytic H2 evolution from an aqueous methanol solution. The results showed that activity of the catalyst not only depends on the morphology of its catalysts, but also on the crystalinity and surface area. Hydrogen production of TiO2 NT was about three times higher than TiO2 P25 and TiO2 NW was two times higher than TiO2P25."