Javier Jesús Ramírez Hernández

Bio: Javier Jesús Ramírez Hernández is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Colloidal gold & Volcano. The author has an hindex of 15, co-authored 33 publications receiving 1113 citations. Previous affiliations of Javier Jesús Ramírez Hernández include University of Alicante & Universidad Autónoma del Estado de México.

Electrochemistry of Shape-Controlled Catalysts: Oxygen Reduction Reaction on Cubic Gold Nanoparticles

Abstract: This paper describes the electrochemical behavior of shape controlled, deliberately large Au nanoparticles that have been synthesized using a seed-mediated growth method in the presence of cetyl trimethyl ammonium bromide. Transmission electron microscopy micrographs and selected area electron diffraction patterns revealed 40 nm Au nanoparticles with a preferentially cubic shape suggesting a high amount of (100) surface sites. In situ electrochemical structure-sensitive reactions such as lead underpotential deposition confirm that the surface of the nanoparticles contains a large quantity of wide (100) domains. As a consequence, the nanoparticles showed a very high catalytic activity for the four electron oxygen reduction paths in alkaline media. Thus, water was obtained as the final product of the reaction in the whole potential range, while hydrogen peroxide was obtained only in the lower potential region, in a similar way as reported for Au (100) electrodes.

Characterization of the Surface Structure of Gold Nanoparticles and Nanorods Using Structure Sensitive Reactions

Abstract: The surface structure of gold nanorods has been determined by studying the behavior of electrochemical reactions sensitive to the structure and compared to that obtained by other structure characterization techniques. Lead underpotential deposition (UPD) reveals that the surface of the nanorods is composed by (111) and (110) domains, while (100) domains are practically absent from the surface. In the case of the oxygen reduction reaction, the formation of hydrogen peroxide as a final product of the reaction in the whole potential range also indicates that (100) domains are absent on the surface of the nanoparticles, corroborating the previous result. These results are compared with other surface structure information provided by other techniques.

Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

Abstract: We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

Shape control in gold nanoparticle synthesis

Abstract: In this tutorial review, we summarise recent research into the controlled growth of gold nanoparticles of different morphologies and discuss the various chemical mechanisms that have been proposed to explain anisotropic growth. With the overview and discussion, we intended to select those published procedures that we consider more reliable and promising for synthesis of morphologies of interest. We expect this to be interesting to researchers in the wide variety of fields that can make use of metal nanoparticles.

New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism

Abstract: The effect of pH on the hydrogen oxidation and evolution reaction (HOR/HER) rates is addressed for the first time for the three most active monometallic surfaces: Pt, Ir, and Pd carbon-supported catalysts. Kinetic data were obtained for a proton exchange membrane fuel cell (PEMFC; pH ≈ 0) using the H2-pump mode and with a rotating disk electrode (RDE) in 0.1 M NaOH. Our findings point toward: (i) a similar ≈100-fold activity decrease on all these surfaces when going from low to high pH; (ii) a reaction rate controlled by the Volmer step on Pt/C; and (iii) the H-binding energy being the unique and sole descriptor for the HOR/HER in alkaline electrolytes. Based on a detailed discussion of our data, we propose a new mechanism for the HOR/HER on Pt-metals in alkaline electrolytes.

Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries

Abstract: Sub-nanometre sized metal clusters, with dimensions between metal atoms and nanoparticles, have attracted more and more attention due to their unique electronic structures and the subsequent unusual physical and chemical properties. However, the tiny size of the metal clusters brings the difficulty of their synthesis compared to the easier preparation of large nanoparticles. Up to now various synthetic techniques and routes have been successfully applied to the preparation of sub-nanometre clusters. Among the metals, gold clusters, especially the alkanethiolate monolayer protected clusters (MPCs), have been extensively investigated during the past decades. In recent years, silver and copper nanoclusters have also attracted enormous interest mainly due to their excellent photoluminescent properties. Meanwhile, more structural characteristics, particular optical, catalytic, electronic and magnetic properties and the related technical applications of the metal nanoclusters have been discovered in recent years. In this critical review, recent advances in sub-nanometre sized metal clusters (Au, Ag, Cu, etc.) including the synthetic techniques, structural characterizations, novel physical, chemical and optical properties and their potential applications are discussed in detail. We finally give a brief outlook on the future development of metal nanoclusters from the viewpoint of controlled synthesis and their potential applications.

Oxygen Reduction in Alkaline Media: From Mechanisms to Recent Advances of Catalysts

Abstract: The oxygen reduction reaction (ORR) is an important electrode reaction for energy storage and conversion devices based on oxygen electrocatalysis. This paper introduces the thermodynamics, reaction kinetics, reaction mechanisms, and reaction pathways of ORR in aqueous alkaline media. Recent advances of the catalysts for ORR were extensively reviewed, including precious metals, nonmetal-doped carbon, carbon–transition metal hybrids, transition metal oxides with spinel and perovskite structures, and so forth. The applications of those ORR catalysts to zinc–air batteries and alkaline fuel cells were briefly introduced. A concluding remark summarizes the current status of the reaction pathways, advanced catalysts, and the future challenges of the research and development of ORR.