Photocatalytic reactions to convert CO 2 and H 2 O into solar fuels using only solar irradiation have been investigated in this work. For this purpose, titanosilicate ETS-10 was decorated with Cu 2 O and CuO nanoparticles and their properties were analyzed by different techniques. The final materials were applied in photoreduction of CO 2 in gas phase under 20 h of solar irradiation. In the final, the products oxygen, acetic acid, formaldehyde and methanol were detected by chromatographic techniques. Photoluminescence and electrochemical studies indicate the interaction between Cu x O nanoparticles and Ti-O-Ti-O on the surface of ETS-10, corroborating with the results obtained in the photocatalytic experiments. The best CO 2 photoconversion efficiencies into methanol were obtained when using ETS-10/Cu x O compared to pure ETS-10. Another important finding in this study is the fact that the reactions were carried out in the gas phase and no scavenge donors were employed.Keywords: CO 2 photoreduction, ETS-10 photocatalyst, oxygenated products, copper oxide, solar irradiation IntroductionIn the last 40 years, CO 2 emissions from fossil fuel combustion and industrial processes contributed with about 78% of the total greenhouse gases (GHG) emissions. 1 Different methods to consume CO 2 have been investigated, such as thermochemical conversion, 2-4 electrochemical reduction, [5][6][7] and photocatalytic reduction of CO 2 and water into hydrocarbons or solar fuels. [8][9][10] The use of solar energy has been highlighted as an alternative to obtain clean energy while simultaneously reducing the CO 2 concentration in the atmosphere. 11 Many chemicals are reported to be produced from water and CO 2 : formic acid, 12,13 acetic acid, 14,15 formaldehyde, 16 methanol [17][18][19] and methane. 20,21 Using a combination of metaloxides and co-catalysts we have already demonstrated the feasibility to produce both methane and methanol. 22 The first and principal step in CO 2 reduction is the oxidation of H 2 O molecules into oxygen and protons (equation 1), following the sequence described in equations 1-5. 23 Several works report the conversion to oxygenated chemicals by using sacrificial compounds, such as NaOH, 24 Titanosilicate ETS-10 (Engelhard titanium silicate) was first reported in the literature by Chapman and Roe 28 in 1990, however its structure was elucidated only in 1994 by Anderson et al. 29 using sophisticated techniques as highresolution transmission electron microscopy (HRTEM), nuclear magnetic resonance (NMR) and molecular simulations. The most interesting feature is that the ETS-10 contains a periodic structure of quantum semiconductor wires of [-O-Ti-O-Ti-] formed by TiO 6 octahedra isolated along the structure. The pores (ca. 0.67 nm diameter) run along [100] and [010] directions. [30][31][32][33] These properties make ETS-10 unique, because a short Ti-O bond length (1.71-2.11 Å) along the axial direction would not be possible outside of a zeolite framework. 34 This material absorbs ETS-10 Modified with Cu ...

Here, Pd nanoparticles supported on ZnO were prepared by the alcohol-reduction and the borohydride-reduction methods, and their efficiency towards the photocatalytic conversion of methane under mild conditions were evaluated. The resulting Pd/ZnO photocatalysts were characterized by X-ray fluorescence, X-ray diffraction, X-ray photoelectron spectroscopy, UV–Vis, and transmission electron microscopy. The reactions were performed with the photocatalysts dispersed in water in a bubbling stream of methane under UV-light illumination. The products formed were identified and quantified by gas chromatography (GC-FID/TCD/MSD). The principal products formed were C2H6 and CO2 with minor quantities of C2H4 and CO. No H2 production was observed. The preparation methods influenced the size and dispersion of Pd nanoparticles on the ZnO, affecting the performance of the photocatalysts. The best performance was observed for the photocatalyst prepared by borohydride reduction with 0.5 wt% of Pd, reaching a C2H6 production rate of 686 µmol·h−1·g−1 and a C2H6 selectivity of 46%.

The processes currently used in the chemical industry for methane conversion into fuels and chemicals operate under extreme conditions like high temperatures and pressures. In this sense, the search for methane conversion under mild conditions remains a great challenge. This review aims to summarize the use semiconductors and metal-semiconductors as heterogeneous photocatalysts for methane conversion under mild conditions into valuable products. First, a brief presentation of photochemical conversion of methane is provided and then the focus of this review on the use of heterogeneous photocatalysts for methane conversion are described. Finally, the main challenges and opportunities are discussed.

Au/Ga2O3 photocatalysts were prepared by three different methods (pre-formed Au nanoparticles, borohydride reduction, and impregnation-H2 reduction) and tested as photocatalysts for methane conversion coupling with hydrogen production from water. The...

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Ao Inami-CNPq pela bolsa concedida, a CAPES e a FAPESP pelo apoio financeiro. Ao Departamento de Química da FFCLRP pela oportunidade oferecida. Ao prof. Osvaldo Antônio Serra por essa grande oportunidade de aprendizado, orientação e enriquecimento deste e de outros trabalhos. Ao prof. Paulo Sérgio Calefi pela orientação durante a iniciação científica, pois sem essa primeira oportunidade, jamais estaria concluindo o meu mestrado; por me incentivar desde o início a continuar meus estudos. Aos professores deste departamento por agregar conhecimento a todos os alunos dessa instituição. Aos membros do Laboratório de Terras Raras-A Juliana-(D. Ju), por sempre ter me auxiliado no laboratório para o desenvolvimento desse e outros trabalhos; ao Paulo César (PC) pelas várias medidas fluorométricas e discussões sobre conceitos da química das Terras Raras; ao Vitor, Ana Cecília, Jonathan e Ariane pela convivência no laboratório. A Janete pela ajuda no projeto dos nanotubos de titânio; ao Cláudio por sempre estar disposto a nos auxiliar e pela contribuição que deu neste trabalho. Ao pessoal do laboratório de Bioinorgânica-Lucas Skywalker, pelos inúmeros momentos de incontroláveis gargalhadas e pelas sugestões ao trabalho dos nanotubos. Aos ex-ICs Francisco (Chiko) e Nicholas (Shrek) pelos momentos de risada. Aos ICs Fabrício, Fernanda (D. Fer), Daniela (D. Dani) e Fábio pela amizade e por sempre permitir que eu utilizasse o laboratório. Ao meu namorado, Guilherme pelo companheirismo, amor e conselhos; se não fosse você jamais teria prestado a prova da USP-RP. Aos amigos da Casa 12: Msc. Felipe, Prof. Dra.Jaqueline (Jaque), Prof. Msc. Gabriela (D. Gabí), Grace Kelly (D. Grace), Janaína (D. Jana), Lidervan (Lider) e vi respectivos, pela grande amizade, risadas, conselhos, saídas ás quartas e quintas. Vocês me mostraram o verdadeiro sentido de amizade e companheirismo. Vocês são muito especiais!!!.