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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.

https://dr.ntu.edu.sg/bitstream/10220/16761/1/long-range balanced electron- and hole-transport lengths in organic-inorganic ch3nh3pbi3.pdf

Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3

There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.

Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Transition-metal compound (nitrides, carbides, phosphides, etc.) nanomaterials are under intensive research as potential advanced electrode materials in batteries, supercapacitors, and electrocatalytic water splitting. The radio-frequency plasma-assisted technique has emerged as a powerful tool in inducing nanoscale reactions, doping, defects, and nanostructure of electrode materials in high precision. Here, the recent application of the plasma-assisted method in rapid conversion reactions and functionalization of electrode materials, which includes metal nitrides, phosphides, and carbon, is highlighted. The uniqueness and advantage of the plasma technique is introduced, along with the challenge for application to industrial electrode materials.

Plasma for Rapid Conversion Reactions and Surface Modification of Electrode Materials

Unique nanorods/nanoparticles/nanoflakes (NRs/NPs/NFs) WO3 triple-layers are grown on a metallic W foil by a simple one-step anodization method. The triple-layered structure is formed through a self-organization process, the film thickness (up to 3 μm) being controlled by the anodization time. A first layer made of an array of WO3 densely-packed vertically-aligned NRs (1.2–1.4 μm in height) grow atop the tungsten foil, followed by a second layer of small NPs (50–80 nm) and finally a third layer made of rectangular NFs (200–300 nm). When irradiated by white light in a photoelectrochemical cell these WO3 triple-layers generate a photocurrent as high as 0.9 mA cm−2 at 1.2 V/RHE. Moreover, we show that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.

Triple-layered nanostructured WO3 photoanodes with enhanced photocurrent generation and superior stability for photoelectrochemical solar energy conversion

Transition metal (oxy)hydroxides are a class of promising non-noble metal based electrocatalysts utilized for the water oxidation reaction but suffer from poor electrical conductivity. Herein, we report on CNTs@ultrathin FeOOH nanoflake core/shell networks on a carbon cloth (CNTs@FeOOH/CC) for the oxygen evolution reaction (OER). With the assistance of a layer of ZnO formed via atomic layer deposition (ALD), ultrathin FeOOH nanoflakes are uniformly grown on CNTs. The CNT cores serve as highly conductive channels to facilitate the transfer of electrons, which effectively enhances the electrical conductivity of FeOOH. Furthermore, the interwoven network structure increases the mass loading and utilization of FeOOH. As a result, the CNTs@FeOOH/CC catalyst exhibits a high OER performance, with features such as a low onset overpotential, large anodic current density, small Tafel slope and excellent long-term electrolysis durability, which are highly desirable for a promising OER electrocatalyst.

Ultrathin CNTs@FeOOH nanoflake core/shell networks as efficient electrocatalysts for the oxygen evolution reaction

Herein, mesoporous Ni-doped Co3O4 nanowire (NW) arrays are reported as a highly efficient and low-cost catalyst for oxygen reduction reaction (ORR) in alkaline electrolyte. The Ni doping affords more electroactive sites and enhanced conductivity, and the mesoporous structure provides increased surface exposure, which may improve ion/electron transport and reduce charge transfer resistance. The NW arrays exhibit a high ORR activity with a four-electron transfer reaction in alkaline media, a half-wave potential of 0.86 V vs. RHE and a superior stability when compared to the commercial Pt (20 wt%)/C catalyst. Our results suggest that the mesoporous Ni-doped Co3O4 NW arrays could be a promising ORR catalyst for fuel cells and metal–air batteries.

Efficient oxygen reduction reaction using mesoporous Ni-doped Co3O4 nanowire array electrocatalysts

Cuprous oxide Cu2O is a promising p-type semiconductor for photoelectrochemical (PEC) solar hydrogen generation because it has a suitable bandgap (Eg?=?2.0?2.2 eV) and a band alignment adapted to water reduction. In addition, metallic Cu is earth-abundant thus making Cu2O a low-cost material. However, the reduction potential of Cu2O into metallic Cu (0.47 V versus RHE) is lower than that of water which induces a severe instability under irradiation in a PEC cell. Therefore, our recent efforts focused on the growth of a protective overlayer on top of Cu2O in order to stabilize Cu2O when used as a photocathode in an aqueous electrolyte. Among potential protective materials cuprous sulphide Cu2S is another p-type semiconductor with a 1.2 eV bandgap and an appropriate energy level alignment with Cu2O that would allow electrons flowing to the interface. We present here an original and simple method aimed at protecting a compact layer (CL) or nanowires (NWs) of Cu2O with a Cu2S coating. Our method is based on the ions exchange reaction (IER) of O2? into S2? at the surface of Cu2O itself in a solution-containing Na2S as the sulphur source. The local surface IER implies the formation of a conformal and uniform coating independently on the starting Cu2O morphology, CLs or NWs. As expected, coating Cu2O photocathodes by a conformal Cu2S layer improves their stability and PEC performances.

https://iopscience.iop.org/article/10.1088/0957-4484/26/18/185401/pdf

Hong Jin Fan

Papers

Plasma for Rapid Conversion Reactions and Surface Modification of Electrode Materials

Triple-layered nanostructured WO3 photoanodes with enhanced photocurrent generation and superior stability for photoelectrochemical solar energy conversion

Ultrathin CNTs@FeOOH nanoflake core/shell networks as efficient electrocatalysts for the oxygen evolution reaction

Efficient oxygen reduction reaction using mesoporous Ni-doped Co3O4 nanowire array electrocatalysts

Conformal Cu2S-coated Cu2O nanostructures grown by ion exchange reaction and their photoelectrochemical properties