Synthesis of Gold Nanoparticles and Incorporation to a Porous Nickel Electrode to Improve its Catalytic Performance Towards the Hydrogen Evolution Reaction

[EN] Gold nanoparticles (AuNPs) were successfully synthesized by a facile chemical reduction method in the presence of the stabilizer polyvinylpyrrolidone and characterized by UV-vis spectroscopy and transmission electron microscopy. The gold nanoparticles were then incorporated onto the surface of a porous Ni electrode by simple addition of the nanoparticles suspension, followed by heat treatment at 350 degrees C for 1 h under nitrogen atmosphere. The modified electrode was morphologically characterized by field emission scanning electron microscopy. Then, the effect of the modification with Au nanoparticles was studied in the hydrogen evolution reaction (HER) by pseudo-steady-state polarization curves and electrochemical impedance spectroscopy (EIS), at different temperatures and compared with a pure porous Ni electrode. The modified electrode showed a clear improvement in its catalytic performance mainly due to the intrinsic catalytic activity of the Au nanoparticles. From the Tafel representations and the EIS, it was estimated that the HER on the electrode modified with AuNPs takes place by the Volmer-Heyrovsky mechanism.Ramiro Medina Orta is grateful to Consejo Nacional Ciencia y Tecnologia and Consejo Potosino de Ciencia y Tecnologia for the doctorate scholarship 472041. Also, he wishes to thank the Instituto de Metalurgia of Universidad Autonoma de San Luis Potosi for the opportunity of a research stay. We also thank Dr. Nubia Arteaga Larios and M.M.I.M. Martha Alejandra Lomeli Pacheco (Instituto de Metalurgia, Universidad Autonoma de San Luis Potosi) for their help with the UV-vis spectroscopy.Medina-Orta, R.; Labrada-Delgado, GJ.; Silva-Pereyra, HG.; Ortega Navarro, EM.; Pérez-Herranz, V.; Sánchez-Loredo, MG. (2022). Synthesis of Gold Nanoparticles and Incorporation to a Porous Nickel Electrode to Improve its Catalytic Performance Towards the Hydrogen Evolution Reaction. Electrocatalysis. 13(1):47-61. https://doi.org/10.1007/s12678-021-00690-7476113

Photodegradation Diuron herbicide with TiO2-Al2O3 catalysts supported on graphene nanoplatelets

Objective: To photodegrade Diuron with TiO2-Al2O3 nanomaterials supported on graphene nanoplatelets (GnPs) Design/methodology/approach: The synthesis of the materials was carried out by the sol-gel method under mild conditions. Subsequently, the obtained materials were subjected to thermal processing for structural stabilization and pulverized. Synthesized nanomaterials were then characterized by nitrogen adsorption/desorption, X-ray diffraction, scanning electron microscopy, and Uv-Vis spectroscopy. Results: The adsorption/desorption results indicated that the ternary TiO2-Al2O3/GnPs nanomaterials were found to have complex porosity, which suggested that TiO2-Al2O3 was formed on agglomerated GnPs. X-ray diffraction data revealed that the anatase phase of TiO2 and the g-Al2O3 phase coexist with the crystalline phase of graphene. The morphology of the materials indicates that the nanoplatelets were randomly dispersed in a continuous mixed oxide phase. About the UV analysis, the presence of GnPs at 1 wt % concentration reduces the band gap by 6%. Limitations on study/implications: The physical and chemical properties of GnPs make the material an excellent candidate for the degradation of pollutants by photocatalysis. Findings/conclusions: The addition of GnPs improved the Diuron degradation, probably by forming a nanostructured interface or heterojunction.  Objective: To photodegrade Diuron with TiO2-Al2O3 nanomaterials supported on graphene nanoplatelets (GnPs) Design/methodology/approach: The synthesis of the materials was carried out by the sol-gel method under mild conditions. Subsequently, the obtained materials were subjected to thermal processing for structural stabilization and pulverized. Synthesized nanomaterials were then characterized by nitrogen adsorption/desorption, X-ray diffraction, scanning electron microscopy, and Uv-Vis spectroscopy. Results: The adsorption/desorption results indicated that the ternary TiO2-Al2O3/GnPs nanomaterials were found to have complex porosity, which suggested that TiO2-Al2O3 was formed on agglomerated GnPs. X-ray diffraction data revealed that the anatase phase of TiO2 and the g-Al2O3 phase coexist with the crystalline phase of graphene. The morphology of the materials indicates that the nanoplatelets were randomly dispersed in a continuous mixed oxide phase. About the UV analysis, the presence of GnPs at 1 wt % concentration reduces the band gap by 6%. Limitations on study/implications: The physical and chemical properties of GnPs make the material an excellent candidate for the degradation of pollutants by photocatalysis. Findings/conclusions: The addition of GnPs improved the Diuron degradation, probably by forming a nanostructured interface or heterojunctio

Insights into Equilibrium and Adsorption Rate of Phenol on Activated Carbon Pellets Derived from Cigarette Butts

In the present work, the preparation of activated carbon pellets from cigarette butts by thermal treatment was evaluated. The morphological, textural, topological, and surface chemical properties were studied by SEM-EDX, N2 adsorption, Raman, and FTIR spectroscopy. For adsorption assays, activated carbon was tested for the adsorption of phenol as a model molecule at different solution pH, temperature, and type of water. In addition, leaching tests before and after carbonization were conducted to evaluate the lixiviation of ions present in the solid. The results revealed a microporous material, composed of cylindrical fibers (thickness of 13 µm) with a microporous area of 713 m2/g and narrow and uniform slit-shaped pores (0.4–0.8 nm). The surface chemistry analysis evidenced the presence of oxygenated groups (carboxylic, esters, and phenolics). Activated carbon leaching tests indicated that the concentrations of the leached ions did not exceed the maximum permissible limit for drinking water. Phenol adsorption revealed an exothermic process with a maximum adsorption capacity of 272 mg/g at 10 °C. Finally, it was confirmed that phenol diffusion was drastically affected by hindered phenomena due to the similarity in the molecular size of phenol and the average size of micropores, and as a result an effective diffusion coefficient between 6.10 × 10−0 and 5.50 × 10−12 cm2/s and a maximum tortuosity value of 3.3 were obtained

Coexistence of two-photon absorption and saturable absorption in ion-implanted platinum nanoparticles in silica plates

"Platinum nanoparticles were nucleated in a high-purity silica matrix by an ion-implantation method. The third-order nonlinear optical response of the samples was studied using femtosecond pulses at 800 nm with the z-scan technique; picosecond pulses at 532 nm using a self-diffraction approach; and nanosecond pulses at 532 nm employing a vectorial two-wave mixing experiment. Nanosecond and picosecond explorations indicated an important thermal process participating in the optical Kerr effect evaluated. However, femtosecond results allowed us to distinguish a purely electronic response, related exclusively to ultrafast refractive and absorptive nonlinearities. Femtosecond experiments pointed out the possibility to switch the dominant physical mechanism responsible for the nonlinear optical absorption in the sample. This opens the potential for controlling quantum mechanisms of optical nonlinearity by femtosecond interactions.