Geonel Rodriguez Gattorno - Academia.edu (original) (raw)

Papers by Geonel Rodriguez Gattorno

In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in ... more In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in solution by four different chemical routes is reported. Classic routes such as borohydride reduction in aqueous media and the so-called polyol methodology were used to obtain the cobalt nanostructures to be studied. Using CTAB as surfactant, cobalt hollow nanostructures were obtained. The use of strong reducing agents, like sodium borohydride, favors the formation of quasi-monodispersed nanoparticles of about 2 nm size but accompanied with impurities; for hydrazine (a mild reducer), nanoparticles of larger size are obtained which organize in spherical microagglomerates. Valuable information on the particles thermal stability and on nature of the species anchored at their surface was obtained from thermogravimetric curves. The samples to be studied were characterized from UV-vis, IR, X-ray diffraction, and electron microscopy images (scanning and transmission).

The Journal of Physical Chemistry B

International Journal of Hydrogen Energy

Abstract The use of solar energy through thermochemical processes is an important approach to dri... more Abstract The use of solar energy through thermochemical processes is an important approach to drive endothermic reactions to produce solar fuels such as hydrogen or syngas. This work reports the preparation and the thermophysical characterization of a porous composite based on zirconium dioxide (ZrO2) and nickel cobaltite (NiCo2O4) nanoparticles for applications in thermochemical processes at high temperatures. The ZrO2 supports were modified with NiCo2O4 nanoparticles by a low-cost and straightforward impregnation process following by thermal treatment at 773 K. The impregnated NiCo2O4 obtained is formed by nanoparticles with an average size of 50 nm favoring a complete and homogenous covering of ZrO2 supports. The thermal properties of ZrO2 supports and NiCo2O4@ZrO2 composites were evaluated in the temperature range from 300 to 1250 K. Besides, the solar absorbance and thermal emittance values were measured. After depositing the nickel cobaltite nanoparticles in the supports, it has been observed that the thermal properties have changed slightly so that the added nanoparticles do not significantly change the thermal performance of the materials. The nickel cobaltite nanoparticles deposited on the surface of the ZrO2 supports causes a strong increase in solar absorbance. This improves the efficiency of solar thermal conversion. Our results have shown that NiCo2O4@ZrO2 has excellent characteristics to be used in solar thermochemical processes.

Journal of Colloid and Interface Science, 2005

One-step room-temperature synthesis of nanocrystalline Mn3O4 hausmannite, without heating posttre... more One-step room-temperature synthesis of nanocrystalline Mn3O4 hausmannite, without heating posttreatment, was carried out from a simple dissolution of manganese(II) acetate in a mixture of N,N'-dimethylformamide (DMF) and water. Homogeneous nanocrystals like rods were obtained, with an average width and length of 6.6+/-1.2 nm and 17.4+/-4.1 nm, respectively, and a preferential growth along the 001 direction. Magnetization measurements on a powdered sample showed ferrimagnetic behavior at low temperatures. Under zero-field cooling (ZFC) measurement at 100 Oe, the observed blocking temperature (T(B)) was 37 K.

Materials Chemistry and Physics, 2012

Structural, thermal profiles and kinetic behavior of two different sol-gel samples of MgAl layere... more Structural, thermal profiles and kinetic behavior of two different sol-gel samples of MgAl layered double hydroxides (LDHs) were studied. In situ FT-IR study was used to follow the chemical composition changes, and thermal evolution of specific chemical species in each stage was monitored with a dynamic sampling mass spectrometer (TPD-MS analysis). The identified gas products were mainly OH, H 2 O, CO 2 , and organic species, mainly C 2 H 5 , originated from the alkoxy groups. The thermal evolution of intercalated compounds occurred in at least four steps related to dehydration, dehydroxylation of layers, interlayer anion decomposition, shrinkage and collapse of the layered structure, and finally crystallization of spinel MgAl 2 O 4. Kinetic analysis in terms of activation energy (Ea), suggest that decomposition mechanism is a complex process that involves decomposition of several species and phase transformations.

Photoelectrochemical water splitting is an attractive method to convert solar energy to storable ... more Photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen, however, the materials requirements to achieve this efficiently are challenging: the semiconducting material needs to absorb sunlight efficiently, must to be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue, and it is difficult to fully avoid degradation of the material. In addition, the water reduction and oxidation processes need to occur fast, in order to favorably compete with recombination or surface degradation processes; hence, the kinetic rate constants for charge transfer and surface recombination are very important parameters. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful technique to study the carrier dynamics in a photoelectrochemical cell. The photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined, provided a simple model can be applied.1 In this presentation, we focus on the dynamic properties of p-CuBi2O4 in order to elucidate the rate determining steps that determine the efficiency of photocathodic reactions. In inert aqueous solutions at pH 5, an unfavorable balance exists between the rate constants for charge transfer and surface recombination, which limits the conversion efficiency.2 On the other hand, upon adding H2O2 as an electron acceptor, the photoelectron transfer efficiency is improved related to faster electron transfer to the solution or slower surface recombination due to passivation effects. Strategies to improve the applicability of CuBi2O4 in solar water splitting systems are discussed. The authors gratefully acknowledge CONACYT, SENER and CICY for funding through the Renewable Energy Laboratory of South East Mexico (LENERSE; Project 254667; SP-4), and CONACYT under the Basic Sciences (CB) project A1-S-28734. References “Photoelectrochemical Water Splitting at Semiconductor Electrodes: Fundamental Problems and New Perspectives”. L. M. Peter and K. G. Upul Wijayantha, ChemPhysChem, 15, 1983–1995 (2014). “Charge Transfer and Recombination Dynamics at Inkjet-Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting”. Ingrid Rodríguez-Gutiérrez, Rodrigo García-Rodríguez, Manuel Rodríguez-Pérez, Alberto Vega-Poot, Geonel Rodríguez Gattorno, Bruce A. Parkinson, and Gerko Oskam. J. Phys. Chem. C, 122, 27169−27179 (2018).

Química Nova

The goal of the present study was to determine the potential use of thermal analysis for the meas... more The goal of the present study was to determine the potential use of thermal analysis for the measurement of the light crude oil (LCO) content of standard biodiesel mixtures. Standard samples of biodiesel/LCO blends were prepared with different ratios of biodiesel; LCO: 1:0 (biodiesel only), 1:3, 1:1, 3:1, 0:1 (LCO only). Thermogravimetry (TG) and differential scanning calorimetry were used to determine the usefulness of thermal analysis for quantification of the LCO in the mixtures. Proton nuclear magnetic resonance (1 H NMR) spectroscopy was also used to confirm the composition of the samples. It was found that thermogravimetric curves were not appropriate for the LCO measurements. However, the DSC signal of wax crystallization exhibited a good linear (R 2 = 0.99) correlation with the LCO content in the blend. Furthermore, it was shown that aliphatic protons (-CH 2-) n in biodiesel and light crude oil can also be used to determine LCO in biodiesel/LCO blends.

Materials Research Express

The Journal of Physical Chemistry C

Advances in Materials Science and Engineering

Owing to its distinctive physicochemical properties, nickel-cobalt mixed oxide (NiCo2O4) has beco... more Owing to its distinctive physicochemical properties, nickel-cobalt mixed oxide (NiCo2O4) has become a promising and innovative material for applications in many technological fields. The design of fast and reliable techniques for the deposition of this material is essential in the development of applications. In this work, NiCo2O4 films were successfully prepared by an inkjet printing technique using a suitable ink obtained from metal nitrates in a glycerol-water mixture. In order to deposit well-defined and uniform film patterns, the instrumental parameters such as drop spacing and inkjet voltage have been explored. The pure crystalline bimetallic nickel cobaltite oxide is obtained at 500°C with a homogeneous compositional distribution along the film. The average thickness observed by scanning electron microscopy is around 490 nm, whereas X-ray photoelectron spectroscopy analysis revealed that the film surface presents mixed oxidation states for both metals: Co2+, Co3+, Ni2+, and N...

We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite str... more We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite structures, using amorphous titania as a common starting material. Phase formation was achieved by hydrothermal treatment at elevated temperatures with the appropriate reactants. Anatase nanoparticles were obtained using acetic acid, while phase-pure rutile and brookite nanoparticles were obtained with hydrochloric acid at a different concentration. The nanomaterials were characterized using x-ray diffraction, UV-visible reflectance spectroscopy, dynamic light scattering, and transmission electron microscopy. We propose that anatase formation is dominated by surface energy effects, and that rutile and brookite formation follows a dissolution-precipitation mechanism, where chains of sixfold-coordinated titanium complexes arrange into different crystal structures depending on the reactant chemistry. The particle growth kinetics under hydrothermal conditions are determined by coarsening and aggregation-recrystallization processes, allowing control over the average nanoparticle size.

1er. Simposio de Tecnología Avanzada CICATA-IPN México DF, Junio 16-20, 2008 3 Síntesis y caracte... more 1er. Simposio de Tecnología Avanzada CICATA-IPN México DF, Junio 16-20, 2008 3 Síntesis y caracterización de nanoestructuras de Oxido de cobre I María del Carmen Téllez Juárez, Geonel Rodríguez Gattorno, Edilso Reguera Ruiz 1Centro de Investigación en Ciencia Aplicada ...

Solar Hydrogen and Nanotechnology II, 2007

Thermochimica Acta, 2005

In the present study was combined the use of high resolution TGA with the isoconversion method, g... more In the present study was combined the use of high resolution TGA with the isoconversion method, giving us a suitable methodology for determining the stages that occur during a reaction, and providing further insights about the kinetics of the processes involved. As a model reaction was used the thermal dehydration of KNbWO 6 ·H 2 O. The results shown that the dehydration process is controlled by internal water diffusion (intra-crystallite); with activation energy values between 43 and 36 kJ/mol. This value is consistent with a diffusion mechanism dominated by van der Waals attractions. The estimated kinetic parameters are supported with a structural analysis, that suggest lower dimensionality character for water diffusion due to the specific orientations of 1 1 0 open channels in the pyrochlore framework. This would explain why the two-dimensional (D2) mechanism appears to be the most probable.

In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in ... more In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in solution by four different chemical routes is reported. Classic routes such as borohydride reduction in aqueous media and the so-called polyol methodology were used to obtain the cobalt nanostructures to be studied. Using CTAB as surfactant, cobalt hollow nanostructures were obtained. The use of strong reducing agents, like sodium borohydride, favors the formation of quasi-monodispersed nanoparticles of about 2 nm size but accompanied with impurities; for hydrazine (a mild reducer), nanoparticles of larger size are obtained which organize in spherical microagglomerates. Valuable information on the particles thermal stability and on nature of the species anchored at their surface was obtained from thermogravimetric curves. The samples to be studied were characterized from UV-vis, IR, X-ray diffraction, and electron microscopy images (scanning and transmission).

The Journal of Physical Chemistry B

International Journal of Hydrogen Energy

Abstract The use of solar energy through thermochemical processes is an important approach to dri... more Abstract The use of solar energy through thermochemical processes is an important approach to drive endothermic reactions to produce solar fuels such as hydrogen or syngas. This work reports the preparation and the thermophysical characterization of a porous composite based on zirconium dioxide (ZrO2) and nickel cobaltite (NiCo2O4) nanoparticles for applications in thermochemical processes at high temperatures. The ZrO2 supports were modified with NiCo2O4 nanoparticles by a low-cost and straightforward impregnation process following by thermal treatment at 773 K. The impregnated NiCo2O4 obtained is formed by nanoparticles with an average size of 50 nm favoring a complete and homogenous covering of ZrO2 supports. The thermal properties of ZrO2 supports and NiCo2O4@ZrO2 composites were evaluated in the temperature range from 300 to 1250 K. Besides, the solar absorbance and thermal emittance values were measured. After depositing the nickel cobaltite nanoparticles in the supports, it has been observed that the thermal properties have changed slightly so that the added nanoparticles do not significantly change the thermal performance of the materials. The nickel cobaltite nanoparticles deposited on the surface of the ZrO2 supports causes a strong increase in solar absorbance. This improves the efficiency of solar thermal conversion. Our results have shown that NiCo2O4@ZrO2 has excellent characteristics to be used in solar thermochemical processes.

Journal of Colloid and Interface Science, 2005

One-step room-temperature synthesis of nanocrystalline Mn3O4 hausmannite, without heating posttre... more One-step room-temperature synthesis of nanocrystalline Mn3O4 hausmannite, without heating posttreatment, was carried out from a simple dissolution of manganese(II) acetate in a mixture of N,N'-dimethylformamide (DMF) and water. Homogeneous nanocrystals like rods were obtained, with an average width and length of 6.6+/-1.2 nm and 17.4+/-4.1 nm, respectively, and a preferential growth along the 001 direction. Magnetization measurements on a powdered sample showed ferrimagnetic behavior at low temperatures. Under zero-field cooling (ZFC) measurement at 100 Oe, the observed blocking temperature (T(B)) was 37 K.

Materials Chemistry and Physics, 2012

Structural, thermal profiles and kinetic behavior of two different sol-gel samples of MgAl layere... more Structural, thermal profiles and kinetic behavior of two different sol-gel samples of MgAl layered double hydroxides (LDHs) were studied. In situ FT-IR study was used to follow the chemical composition changes, and thermal evolution of specific chemical species in each stage was monitored with a dynamic sampling mass spectrometer (TPD-MS analysis). The identified gas products were mainly OH, H 2 O, CO 2 , and organic species, mainly C 2 H 5 , originated from the alkoxy groups. The thermal evolution of intercalated compounds occurred in at least four steps related to dehydration, dehydroxylation of layers, interlayer anion decomposition, shrinkage and collapse of the layered structure, and finally crystallization of spinel MgAl 2 O 4. Kinetic analysis in terms of activation energy (Ea), suggest that decomposition mechanism is a complex process that involves decomposition of several species and phase transformations.

Photoelectrochemical water splitting is an attractive method to convert solar energy to storable ... more Photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen, however, the materials requirements to achieve this efficiently are challenging: the semiconducting material needs to absorb sunlight efficiently, must to be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue, and it is difficult to fully avoid degradation of the material. In addition, the water reduction and oxidation processes need to occur fast, in order to favorably compete with recombination or surface degradation processes; hence, the kinetic rate constants for charge transfer and surface recombination are very important parameters. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful technique to study the carrier dynamics in a photoelectrochemical cell. The photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined, provided a simple model can be applied.1 In this presentation, we focus on the dynamic properties of p-CuBi2O4 in order to elucidate the rate determining steps that determine the efficiency of photocathodic reactions. In inert aqueous solutions at pH 5, an unfavorable balance exists between the rate constants for charge transfer and surface recombination, which limits the conversion efficiency.2 On the other hand, upon adding H2O2 as an electron acceptor, the photoelectron transfer efficiency is improved related to faster electron transfer to the solution or slower surface recombination due to passivation effects. Strategies to improve the applicability of CuBi2O4 in solar water splitting systems are discussed. The authors gratefully acknowledge CONACYT, SENER and CICY for funding through the Renewable Energy Laboratory of South East Mexico (LENERSE; Project 254667; SP-4), and CONACYT under the Basic Sciences (CB) project A1-S-28734. References “Photoelectrochemical Water Splitting at Semiconductor Electrodes: Fundamental Problems and New Perspectives”. L. M. Peter and K. G. Upul Wijayantha, ChemPhysChem, 15, 1983–1995 (2014). “Charge Transfer and Recombination Dynamics at Inkjet-Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting”. Ingrid Rodríguez-Gutiérrez, Rodrigo García-Rodríguez, Manuel Rodríguez-Pérez, Alberto Vega-Poot, Geonel Rodríguez Gattorno, Bruce A. Parkinson, and Gerko Oskam. J. Phys. Chem. C, 122, 27169−27179 (2018).

Química Nova

The goal of the present study was to determine the potential use of thermal analysis for the meas... more The goal of the present study was to determine the potential use of thermal analysis for the measurement of the light crude oil (LCO) content of standard biodiesel mixtures. Standard samples of biodiesel/LCO blends were prepared with different ratios of biodiesel; LCO: 1:0 (biodiesel only), 1:3, 1:1, 3:1, 0:1 (LCO only). Thermogravimetry (TG) and differential scanning calorimetry were used to determine the usefulness of thermal analysis for quantification of the LCO in the mixtures. Proton nuclear magnetic resonance (1 H NMR) spectroscopy was also used to confirm the composition of the samples. It was found that thermogravimetric curves were not appropriate for the LCO measurements. However, the DSC signal of wax crystallization exhibited a good linear (R 2 = 0.99) correlation with the LCO content in the blend. Furthermore, it was shown that aliphatic protons (-CH 2-) n in biodiesel and light crude oil can also be used to determine LCO in biodiesel/LCO blends.

Materials Research Express

The Journal of Physical Chemistry C

Advances in Materials Science and Engineering

Owing to its distinctive physicochemical properties, nickel-cobalt mixed oxide (NiCo2O4) has beco... more Owing to its distinctive physicochemical properties, nickel-cobalt mixed oxide (NiCo2O4) has become a promising and innovative material for applications in many technological fields. The design of fast and reliable techniques for the deposition of this material is essential in the development of applications. In this work, NiCo2O4 films were successfully prepared by an inkjet printing technique using a suitable ink obtained from metal nitrates in a glycerol-water mixture. In order to deposit well-defined and uniform film patterns, the instrumental parameters such as drop spacing and inkjet voltage have been explored. The pure crystalline bimetallic nickel cobaltite oxide is obtained at 500°C with a homogeneous compositional distribution along the film. The average thickness observed by scanning electron microscopy is around 490 nm, whereas X-ray photoelectron spectroscopy analysis revealed that the film surface presents mixed oxidation states for both metals: Co2+, Co3+, Ni2+, and N...

We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite str... more We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite structures, using amorphous titania as a common starting material. Phase formation was achieved by hydrothermal treatment at elevated temperatures with the appropriate reactants. Anatase nanoparticles were obtained using acetic acid, while phase-pure rutile and brookite nanoparticles were obtained with hydrochloric acid at a different concentration. The nanomaterials were characterized using x-ray diffraction, UV-visible reflectance spectroscopy, dynamic light scattering, and transmission electron microscopy. We propose that anatase formation is dominated by surface energy effects, and that rutile and brookite formation follows a dissolution-precipitation mechanism, where chains of sixfold-coordinated titanium complexes arrange into different crystal structures depending on the reactant chemistry. The particle growth kinetics under hydrothermal conditions are determined by coarsening and aggregation-recrystallization processes, allowing control over the average nanoparticle size.

1er. Simposio de Tecnología Avanzada CICATA-IPN México DF, Junio 16-20, 2008 3 Síntesis y caracte... more 1er. Simposio de Tecnología Avanzada CICATA-IPN México DF, Junio 16-20, 2008 3 Síntesis y caracterización de nanoestructuras de Oxido de cobre I María del Carmen Téllez Juárez, Geonel Rodríguez Gattorno, Edilso Reguera Ruiz 1Centro de Investigación en Ciencia Aplicada ...

Solar Hydrogen and Nanotechnology II, 2007

Thermochimica Acta, 2005

In the present study was combined the use of high resolution TGA with the isoconversion method, g... more In the present study was combined the use of high resolution TGA with the isoconversion method, giving us a suitable methodology for determining the stages that occur during a reaction, and providing further insights about the kinetics of the processes involved. As a model reaction was used the thermal dehydration of KNbWO 6 ·H 2 O. The results shown that the dehydration process is controlled by internal water diffusion (intra-crystallite); with activation energy values between 43 and 36 kJ/mol. This value is consistent with a diffusion mechanism dominated by van der Waals attractions. The estimated kinetic parameters are supported with a structural analysis, that suggest lower dimensionality character for water diffusion due to the specific orientations of 1 1 0 open channels in the pyrochlore framework. This would explain why the two-dimensional (D2) mechanism appears to be the most probable.