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Papers by Luis Alberto Estudillo-Wong

Research paper thumbnail of Oxygen Reduction Reaction Stability on Platinum Nanoparticles Photo-deposited onto Oxide-Carbon composites

Oxide-Carbon composites (TiO2-C) and yttrium-doped TiO2-C (Y:TiO2-C), synthesized via sol-gel rou... more Oxide-Carbon composites (TiO2-C) and yttrium-doped TiO2-C (Y:TiO2-C), synthesized via sol-gel route, were used as supports to photo-deposit platinum nanoparticles (Pt NPs). The physical-chemical proper- ties of these materials were investigated by Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD). The TEM images showed that Pt NPs were agglomerated and deposited onto oxide sites of the com- posites. Pt face-centered cubic, and TiO2 Anatase phases were identified on both Pt/TiO2-C and Pt/Y:TiO2-C samples. The particle size, stacking fault and micro-strain of Pt NPs were estimated by Williamson- Hall method. Compared with Pt/TiO2-C, similar stacking faults as well as increased crystallite sizes and micro-strain values could be observed for Pt/Y:TiO2-C sample, indicating a minimum impact of the rare earth element on Pt. Pt/C was prepared by the same method, and used as a reference catalyst. The strong-metal/support interaction (SMSI) effect induced by the photo-deposition method, in Pt/TiO2-C and Pt/Y:TiO2-C samples, was probed by CO-stripping, and associated to the enhanced stability toward the oxygen reduction reaction (ORR) in acid medium.

Research paper thumbnail of Reacciones (foto)-Electroquímicas Inducidas en la Interfaz Electrodo-Electrolito

Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Ex... more Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Extractivas (ESIQIE)-Instituto Politécnico Nacional (IPN), 57296000, ext. 55146, 55388. C. P. 07738. México D.F. México. *amanzor@ipn.mx RESUMEN La electro-inducción de la reducción de oxígeno, oxidación de hidrógeno y electrólisis del agua son posibles en la interfaz electrodo-electrolito. Las dos primeras corresponden a procesos llevados a cabo en pilas de combustible para generar electricidad. Mientras que la electrolisis del agua produce hidrogeno (HER) y oxigeno (OER). El estudio de éstas reacciones electródicas es fundamental para el desarrollo de dispositivos generadores de electricidad amigables al medio-ambiente. Tomando como base HER y OER, reacciones importantes en la disminución de la contaminación pueden ser (foto)-electro-inducidas. Ejemplo de reacciones controladas por OER es la oxidación de moléculas orgánicas como metanol, etanol, acido fórmico, colorantes, entre otras. Po...

Research paper thumbnail of Interaction of NO during cathodic polarization in alkaline conditions at the interface of Pt-nanostructures supported on C and TiO2-C

Electrochimica Acta, 2014

ABSTRACT The electroreduction of nitric oxide (NO) in alkaline media was carried out on Pt nanopa... more ABSTRACT The electroreduction of nitric oxide (NO) in alkaline media was carried out on Pt nanoparticles (5 wt.% Pt), which were synthesized by the carbonyl route. The as-prepared materials were supported on Carbon Black (XC-72R, C) and TiO2-C composite (10 wt.% TiO2) and deposited on glassy carbon (GC) electrode. X-ray Diffraction (XRD), CO-stripping and hydrogen adsorption-desorption (Hupd) analysis were employed to characterize the structure and electrochemical properties. According to XRD patterns, the particle size increases from 3.95 to 8.98 nm due to the interaction of Pt with TiO2 in the carbon matrix. This modification promotes a better performance during CO-oxidation and proton adsorption-desorption. As a consequence, the performance toward NO-reduction was more important in TiO2-C composite, linked with the electrochemical active-surface area and chemical surface area relationship (ECSA/CSA). It was found that the mechanism for the reduction of nitric oxide toward nitrogen is a bi-functional process with coupled chemical and electrochemical interfacial-reactions with NH2 specie as intermediate, as demonstrated by the induced reduction reaction of NO2− and NO2− + NO, and UV-vis spectrometry.

Research paper thumbnail of TiO2/C composite as a support for Pd-nanoparticles toward the electrocatalytic oxidation of methanol in alkaline media

Electrochimica Acta, 2013

ABSTRACT The electro-oxidation of methanol was studied in alkaline solution on Pd nanoparticles s... more ABSTRACT The electro-oxidation of methanol was studied in alkaline solution on Pd nanoparticles supported on carbon black (XC-72R, C) and TiO2/C composite. The materials were prepared via organic colloid route at 170 °C with 5 wt% of Pd. X-ray diffraction (XRD), PdO monolayer reduction (PdOred) and CO-stripping was employed to characterize both structure and electrochemical properties. According to this, the lattice parameter decreases from 0.3991 to 0.3905 nm due to a possible formation of Pd–Ti alloy. This modification is linked with the electrochemical active surface area (ECSA) decreasing from 22 to 18 m2 g−1. On the other hand, studies as a function of temperature and alcohol concentration indicated that the current for methanol electro-oxidation is higher and more stable at Pd/TiO2–C, with Ea = 44.042 kJ mol−1. Then, it is highly possible that at Pd/TiO2–C, the OH−/OHads couple is adsorbed at the TiO2 sites, increasing the kinetic of methanol oxidation reaction at the catalyst surface.

Research paper thumbnail of Electro-reduction of nitrate species on Pt-based nanoparticles: Surface area effects

Catalysis Today, 2011

The electrochemical reduction of nitrate ions was carried out on Pt-based nanoparticles supported... more The electrochemical reduction of nitrate ions was carried out on Pt-based nanoparticles supported on carbon Vulcan and deposited on a glassy carbon electrode. Different materials were evaluated: synthesized Pt10/C, Pt–Sny/C (y=10, 20wt.%) and commercial Ptx/C-ETEK (x=10, 20 and 40wt.%). Cyclic voltammetry technique was used for this purpose. It was found that the catalytic activity for hydrogen evolution reaction (HER) and

Research paper thumbnail of Electro-reduction of Nitrate and Nitrite Ions on Carbon-Supported Pt Nanoparticles

ECS Transactions, 2008

Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 ... more Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 wt% Pt-Etek/C) have been used to study the electrochemical reduction of NO x ions at different concentrations in alkaline and acid pH. A comparative study between nanostructured and massif platinum was evaluated. Cycling Voltammetry (CV), Rotating Disc Electrode (RDE) and Differential Mass Spectrometry (DEMS) were used for this purpose. Stationary current-potential curves indicate that the adsorption-desorption phenomena take place in two different regions of potential: the electrochemical reduction of NO x ions for potentials ranging from -0.60 to -0.95 V/SCE, and the hydrogen evolution reaction (HER) at potential lower than -0.95 V/SCE. These results confirmed that the reduction of NO x ions follows the order Pt/C > Pt-Etek/C > Pt-massif. DEMS demonstrated the formation of nitrogen species such as N 2 , NO, N 2 O and NO 2 .

Research paper thumbnail of Electroreduction of NOxz species in alkaline medium on Pt nanoparticles

Electrochimica Acta

The electroreduction of nitrogen species in alkaline medium was performed on platinum nanoparticl... more The electroreduction of nitrogen species in alkaline medium was performed on platinum nanoparticles (1–2 nm) with metal loadings of 5 and 10 wt% Pt, synthesized by the chemical carbonyl route. The electrochemically active surface analysis evidences that the real surface area is concomitant to the Pt-loading in the support. The electrochemical analysis put in evidence that nitrite ions were reduced from −0.6 to −0.78 V and the charge transfer step is attributed to the NO2−/NO redox couple. The Tafel slope analysis confirms that from Ep to −0.78 V the reduction of NO occurs via an ECE mechanism. An analysis of Nicholson–Shain schemes and NO-saturated in solution verified these results.

Research paper thumbnail of Oxygen Reduction Reaction Stability on Platinum Nanoparticles Photo-deposited onto Oxide-Carbon composites

Oxide-Carbon composites (TiO2-C) and yttrium-doped TiO2-C (Y:TiO2-C), synthesized via sol-gel rou... more Oxide-Carbon composites (TiO2-C) and yttrium-doped TiO2-C (Y:TiO2-C), synthesized via sol-gel route, were used as supports to photo-deposit platinum nanoparticles (Pt NPs). The physical-chemical proper- ties of these materials were investigated by Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD). The TEM images showed that Pt NPs were agglomerated and deposited onto oxide sites of the com- posites. Pt face-centered cubic, and TiO2 Anatase phases were identified on both Pt/TiO2-C and Pt/Y:TiO2-C samples. The particle size, stacking fault and micro-strain of Pt NPs were estimated by Williamson- Hall method. Compared with Pt/TiO2-C, similar stacking faults as well as increased crystallite sizes and micro-strain values could be observed for Pt/Y:TiO2-C sample, indicating a minimum impact of the rare earth element on Pt. Pt/C was prepared by the same method, and used as a reference catalyst. The strong-metal/support interaction (SMSI) effect induced by the photo-deposition method, in Pt/TiO2-C and Pt/Y:TiO2-C samples, was probed by CO-stripping, and associated to the enhanced stability toward the oxygen reduction reaction (ORR) in acid medium.

Research paper thumbnail of Reacciones (foto)-Electroquímicas Inducidas en la Interfaz Electrodo-Electrolito

Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Ex... more Laboratorio de Electroquímica y Corrosión, Escuela Superior de Ingeniería Química e Industrias Extractivas (ESIQIE)-Instituto Politécnico Nacional (IPN), 57296000, ext. 55146, 55388. C. P. 07738. México D.F. México. *amanzor@ipn.mx RESUMEN La electro-inducción de la reducción de oxígeno, oxidación de hidrógeno y electrólisis del agua son posibles en la interfaz electrodo-electrolito. Las dos primeras corresponden a procesos llevados a cabo en pilas de combustible para generar electricidad. Mientras que la electrolisis del agua produce hidrogeno (HER) y oxigeno (OER). El estudio de éstas reacciones electródicas es fundamental para el desarrollo de dispositivos generadores de electricidad amigables al medio-ambiente. Tomando como base HER y OER, reacciones importantes en la disminución de la contaminación pueden ser (foto)-electro-inducidas. Ejemplo de reacciones controladas por OER es la oxidación de moléculas orgánicas como metanol, etanol, acido fórmico, colorantes, entre otras. Po...

Research paper thumbnail of Interaction of NO during cathodic polarization in alkaline conditions at the interface of Pt-nanostructures supported on C and TiO2-C

Electrochimica Acta, 2014

ABSTRACT The electroreduction of nitric oxide (NO) in alkaline media was carried out on Pt nanopa... more ABSTRACT The electroreduction of nitric oxide (NO) in alkaline media was carried out on Pt nanoparticles (5 wt.% Pt), which were synthesized by the carbonyl route. The as-prepared materials were supported on Carbon Black (XC-72R, C) and TiO2-C composite (10 wt.% TiO2) and deposited on glassy carbon (GC) electrode. X-ray Diffraction (XRD), CO-stripping and hydrogen adsorption-desorption (Hupd) analysis were employed to characterize the structure and electrochemical properties. According to XRD patterns, the particle size increases from 3.95 to 8.98 nm due to the interaction of Pt with TiO2 in the carbon matrix. This modification promotes a better performance during CO-oxidation and proton adsorption-desorption. As a consequence, the performance toward NO-reduction was more important in TiO2-C composite, linked with the electrochemical active-surface area and chemical surface area relationship (ECSA/CSA). It was found that the mechanism for the reduction of nitric oxide toward nitrogen is a bi-functional process with coupled chemical and electrochemical interfacial-reactions with NH2 specie as intermediate, as demonstrated by the induced reduction reaction of NO2− and NO2− + NO, and UV-vis spectrometry.

Research paper thumbnail of TiO2/C composite as a support for Pd-nanoparticles toward the electrocatalytic oxidation of methanol in alkaline media

Electrochimica Acta, 2013

ABSTRACT The electro-oxidation of methanol was studied in alkaline solution on Pd nanoparticles s... more ABSTRACT The electro-oxidation of methanol was studied in alkaline solution on Pd nanoparticles supported on carbon black (XC-72R, C) and TiO2/C composite. The materials were prepared via organic colloid route at 170 °C with 5 wt% of Pd. X-ray diffraction (XRD), PdO monolayer reduction (PdOred) and CO-stripping was employed to characterize both structure and electrochemical properties. According to this, the lattice parameter decreases from 0.3991 to 0.3905 nm due to a possible formation of Pd–Ti alloy. This modification is linked with the electrochemical active surface area (ECSA) decreasing from 22 to 18 m2 g−1. On the other hand, studies as a function of temperature and alcohol concentration indicated that the current for methanol electro-oxidation is higher and more stable at Pd/TiO2–C, with Ea = 44.042 kJ mol−1. Then, it is highly possible that at Pd/TiO2–C, the OH−/OHads couple is adsorbed at the TiO2 sites, increasing the kinetic of methanol oxidation reaction at the catalyst surface.

Research paper thumbnail of Electro-reduction of nitrate species on Pt-based nanoparticles: Surface area effects

Catalysis Today, 2011

The electrochemical reduction of nitrate ions was carried out on Pt-based nanoparticles supported... more The electrochemical reduction of nitrate ions was carried out on Pt-based nanoparticles supported on carbon Vulcan and deposited on a glassy carbon electrode. Different materials were evaluated: synthesized Pt10/C, Pt–Sny/C (y=10, 20wt.%) and commercial Ptx/C-ETEK (x=10, 20 and 40wt.%). Cyclic voltammetry technique was used for this purpose. It was found that the catalytic activity for hydrogen evolution reaction (HER) and

Research paper thumbnail of Electro-reduction of Nitrate and Nitrite Ions on Carbon-Supported Pt Nanoparticles

ECS Transactions, 2008

Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 ... more Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 wt% Pt-Etek/C) have been used to study the electrochemical reduction of NO x ions at different concentrations in alkaline and acid pH. A comparative study between nanostructured and massif platinum was evaluated. Cycling Voltammetry (CV), Rotating Disc Electrode (RDE) and Differential Mass Spectrometry (DEMS) were used for this purpose. Stationary current-potential curves indicate that the adsorption-desorption phenomena take place in two different regions of potential: the electrochemical reduction of NO x ions for potentials ranging from -0.60 to -0.95 V/SCE, and the hydrogen evolution reaction (HER) at potential lower than -0.95 V/SCE. These results confirmed that the reduction of NO x ions follows the order Pt/C > Pt-Etek/C > Pt-massif. DEMS demonstrated the formation of nitrogen species such as N 2 , NO, N 2 O and NO 2 .

Research paper thumbnail of Electroreduction of NOxz species in alkaline medium on Pt nanoparticles

Electrochimica Acta

The electroreduction of nitrogen species in alkaline medium was performed on platinum nanoparticl... more The electroreduction of nitrogen species in alkaline medium was performed on platinum nanoparticles (1–2 nm) with metal loadings of 5 and 10 wt% Pt, synthesized by the chemical carbonyl route. The electrochemically active surface analysis evidences that the real surface area is concomitant to the Pt-loading in the support. The electrochemical analysis put in evidence that nitrite ions were reduced from −0.6 to −0.78 V and the charge transfer step is attributed to the NO2−/NO redox couple. The Tafel slope analysis confirms that from Ep to −0.78 V the reduction of NO occurs via an ECE mechanism. An analysis of Nicholson–Shain schemes and NO-saturated in solution verified these results.