Enhancing the sugars production yield by supporting H3PW12O40 heteropoly acid on activated carbon for use as catalyst in hydrolysis of cellulose

In this work, two catalysts were produced to be used in hydrolysis of cellulose reactions to obtain glucose, araw material used in the production of bioethanol. The heteropoly acid, H3PW12O40 (HPW), reported asstrong and thermally stable acid, was supported on activated carbon (AC) in a ratio varying from 1:1 to 2:1 toproduce the catalysts AC-HPW (1:1) and AC-HPW (2:1). The catalysts were tested in cellulose hydrolysisevaluating some reaction variables and the results show the remarkable dependence of reaction temperature,amount and acidity of the catalyst. The results indicate the advantage of supporting HPW on carbonaceousmaterial for using as catalyst in hydrolysis of cellulose, showing better conversion rate into sugars comparingwith unsupported HPW.Keywords: heteropoly acid; activated carbon support; hydrolysis of cellulose

Synthesis and characterization of alfa-Fe2O3/reduced graphene oxide films in photodegradation of water for hydrogen generation

Orientadores: Ana Flávia Nogueira, Flávio Leandro de SouzaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: O Resumo poderá ser visualizado no texto completo da tese digitalAbstract: The Abstract is available with the full electronic digital documentMestradoQuimica OrganicaMestre em Químic

Enhancing hematite photoanode activity for water oxidation by incorporation of reduced graphene oxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Two effective methods to prepare reduced graphene oxide (rGO)/hematite nanostructured photoanodes and their photoelectrochemical characterization towards water splitting reactions are presented. First, graphene oxide (GO) is reduced to rGO using hydrazine in a basic solution containing tetrabutylammonium hydroxide (TBAOH), and then deposited over the nanostructured hematite photoanodes previously treated at 750 degrees C for 30min. The second method follows the deposition of a paste containing a mixture of hematite nanoparticles and rGO sheets by the doctor-blade method, varying the rGO concentration. Since hematite suffers from low electron mobility, a low absorption coefficient, high recombination rates and slow reaction kinetics, the incorporation of rGO in the hematite can overcome such limitations due to graphene's exceptional properties. Using the first method, the rGO incorporation results in a photocurrent density increase from 0.56 to 0.82mAcm(-2) at 1.23 V-RHE. Our results indicate that the rGO incorporation in the hematite photoanodes shows a positive effect in the reduction of the electron-hole recombination rate.Two effective methods to prepare reduced graphene oxide (rGO)/hematite nanostructured photoanodes and their photoelectrochemical characterization towards water splitting reactions are presented. First, graphene oxide (GO) is reduced to rGO using hydrazine171170177FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2011/19924-2, 2012/24270-4]2011/19924–2; 2012/24270–4sem informaçãoThis work was supported by the Brazilian agencies FAPESP (Grants 2011/19924–2 and 2012/24270–4), CNPq and LNLS. The authors would like to thank Waldemir Moura de Carvalho Junior for the support along this work and Dr. Emre Yassitepe for the XPS measureme

Unraveling the role of single layer graphene as overlayer on hematite photoanodes

In this work, the role of the single layer graphene as overlayer on hematite photoanodes surface was investigated for water oxidation reaction via photoelectrochemical process. Single layer graphene (SLG) was synthesized by chemical vapour deposition (CVD) and transferred from the copper foil to the α-Fe2O3 photoanode surface. To ensure the purity and quality of SLG, elemental composition of the samples was investigated in all steps and no metal (Cu) trace was found after the transference onto the photoanode surface. The photocurrent density of α-Fe2O3/graphene photoanode was increased from 1.25 to 1.64 mA cm−2 at 1.23 VRHE in comparison to bare α-Fe2O3 photoanode. The role of SLG added on α-Fe2O3 and the charge carrier dynamics were investigated combining transient absorption spectroscopy (TAS) and surface photovoltage spectroscopy (SPS). These combined techniques revealed that the photogenerated holes had their lifetime increased as a function of applied bias and after the SLG deposition onto the α-Fe2O3 photoanode surface. As consequence, the photochemical separation and transfer of the photogenerated charge carriers became more efficient in the presence of SLG. The incorporation of SLG on α-Fe2O3 photoanode is believed to suppress the surface traps, enabling holes to diffuse into the solid-liquid interface and promoting water oxidation reaction driven by sunlight irradiation372109118CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão temNão tem2015/23775-3; 2014/11736-0; 2017/11986-5The authors acknowledge the financial support from the Brazilian agency FAPESP (Grants 2015/23775-3 and 2014/11736-0), Capes and CNPq. F. L. S and A. F. N gratefully acknowledge support from FAPESP (Grant 2017/11986-5) and Shell and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation. We also thank Dr. Frank. E. Osterloh from University of California – UC Davis (USA), for providing access to surface photovoltage spectrometer and Dr. Renato Vitalino Gonçalves from USP-São Carlos for the XPS measurement