There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

Noble metal-free hydrogen evolution catalysts for water splitting

A fundamental change has been achieved in understanding surface electrochemistry due to the profound knowledge of the nature of electrocatalytic processes accumulated over the past several decades and to the recent technological advances in spectroscopy and high resolution imaging. Nowadays one can preferably design electrocatalysts based on the deep theoretical knowledge of electronic structures, via computer-guided engineering of the surface and (electro)chemical properties of materials, followed by the synthesis of practical materials with high performance for specific reactions. This review provides insights into both theoretical and experimental electrochemistry toward a better understanding of a series of key clean energy conversion reactions including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reactions by correlating the apparent electrode performance with their intrinsic electrochemical properties. Also, a rational design of electrocatalysts is proposed starting from the most fundamental aspects of the electronic structure engineering to a more practical level of nanotechnological fabrication.

Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions

The urgent need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. Very recently, transition metal phosphides (TMPs) have been proven to be high performance catalysts with high activity, high stability, and nearly ∼100% Faradic efficiency in not only strong acidic solutions, but also in strong alkaline and neutral media for electrochemical hydrogen evolution. In this tutorial review, an overview of recent development of TMP nanomaterials as catalysts for hydrogen generation with high activity and stability is presented. The effects of phosphorus (P) on HER activity, and their synthetic methods of TMPs are briefly discussed. Then we will demonstrate the specific strategies to further improve the catalytic efficiency and stability of TMPs by structural engineering. Making use of TMPs as cocatalysts and catalysts in photochemical and photoelectrochemical water splitting is also discussed. Finally, some key challenges and issues which should not be ignored during the rapid development of TMPs are pointed out. These strategies and challenges of TMPs are instructive for designing other high-performance non-noble metal catalysts.

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Recent advances in transition metal phosphide nanomaterials: synthesis and applications in hydrogen evolution reaction

In this article, we report the synthesis of one-dimensional cadmium sulphide nanowires (CdS NWs) by chemical synthesis approach. These as-synthesized materials were characterized by ultraviolet–visible spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy analysis. These nanowires have an average diameter of ~20 nm and length up to several micrometres. CdS NWs are highly stability and are found to be a very efficient recyclable/reusable (minimum four times without any significant loss) photocatalyst for polyhydroquinoline synthesis under visible light (Halogen lamp, 70 W) at room temperature. This system offers a mild, efficient, and highly economical alternative to the existing protocols in its catalytic activity under visible light irradiation (λ ≥ 420 nm). These findings will open up new opportunities for developing low-cost efficient photocatalyst synthesis of value added intermediates.

Visible light motivated synthesis of polyhydroquinoline derivatives using CdS nanowires

Manipulating the surface to tune plasmonic emission is an exciting fundamental challenge and here we report on the development of unique morphology-dependant optical features of Rh nanostructures prepared by an equilibrium procedure. The emergence of surface plasmon peaks at 375 nm and 474 nm, respectively, is ascribed to truncated and smooth surface of nanospheres in contrast to the absence of surface plasmon for bulk Rh(0) in the visible range. Smaller sized, high surface area domains with well developed, faceted organization are responsible for the promising characteristics of these Rh nanospheres which might be especially useful for potential catalytic, field emission and magnetic applications.

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Tunable optical features from self-organized rhodium nanostructures

Engineering of binary oxide material properties has attracted researchers due to their advance and synergistic application in energy and environment research Thus, substantial efforts are made for exploring novel synthesis approaches for morphological variations, achieving porous network and high surface area enabling fast ion diffusion and charge transfer, particularly required for supercapacitor applications With this motivation, the present work demonstrates the temperature-dependent growth of ZnCo2O4 nanostructures onto flexible stainless-steel mesh (FSSM) substrate via reflux condensation approach and investigating it as a supercapacitor electrode The ZnCo2O4 nanorods/FSSM prepared at 120 °C exhibit a higher specific capacitance of 315 F g−1 at 2 mA cm−2 employing 6 M KOH electrolyte A solid-state ZnCo2O4 nanorod (positive electrode)//FeCo2O4 nanosheet (negative electrode) asymmetric supercapacitor (ASC) device with PVA-KOH gel as an electrolyte is also fabricated The ASC device operated at a potential of 14 V demonstrates a specific capacitance of 1084 F g−1 at 6 mA cm−2 The device delivers a high energy density of 2545 Wh kg−1 at a power density of 3620 W kg−1 and remarkable cyclic stability with 77% capacitance retention over 3000 cycles

Reflux temperature-dependent zinc cobaltite nanostructures for asymmetric supercapacitors

Synthesis of Sb-Doped SnO 2 Nanowires and Hyperbranched Structures

In the present work, Cu2ZnSnS4 (CZTS) thin films have been fabricated onto the glass substrate by simple and economic chemical bath deposition technique1, and the effect of deposition temperature is reported. The deposition temperatures used were 50°C and 60°C for a deposition time of 60 min, which are significantly lower than earlier reports. These CZTS thin films were characterized for optical, electrical, morphological and elemental properties using, UV-Vis spectrophotometer, I-V system for photosensitivity, two probe resistivity system for resistivity, scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy.

Bhaskar R. Sathe

Papers

Visible light motivated synthesis of polyhydroquinoline derivatives using CdS nanowires

Tunable optical features from self-organized rhodium nanostructures

Reflux temperature-dependent zinc cobaltite nanostructures for asymmetric supercapacitors

Synthesis of Sb-Doped SnO 2 Nanowires and Hyperbranched Structures

Temperature dependent fabrication of cost-effective and nontoxic Cu2ZnSnS4 (CZTS) thin films for solar cell