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

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

Polymeric Photocatalysts Based on Graphitic Carbon Nitride

A review on g-C3N4-based photocatalysts

Solar driven catalysis on semiconductors to produce clean chemical fuels, such as hydrogen, is widely considered as a promising route to mitigate environmental issues caused by the combustion of fossil fuels and to meet increasing worldwide demands for energy. The major limiting factors affecting the efficiency of solar fuel synthesis include; (i) light absorption, (ii) charge separation and transport and (iii) surface chemical reaction; therefore substantial efforts have been put into solving these problems. In particular, the loading of co-catalysts or secondary semiconductors that can act as either electron or hole acceptors for improved charge separation is a promising strategy, leading to the adaptation of a junction architecture. Research related to semiconductor junction photocatalysts has developed very rapidly and there are a few comprehensive reviews in which the strategy is discussed (A. Kudo and Y. Miseki, Chemical Society Reviews, 2009, 38, 253–278, K. Li, D. Martin, and J. Tang, Chinese Journal of Catalysis, 2011, 32, 879–890, R. Marschall, Advanced Functional Materials, 2014, 24, 2421–2440). This critical review seeks to give an overview of the concept of heterojunction construction and more importantly, the current state-of-the art for the efficient, visible-light driven junction water splitting photo(electro)catalysts reported over the past ten years. For water splitting, these include BiVO4, Fe2O3, Cu2O and C3N4, which have attracted increasing attention. Experimental observations of the proposed charge transfer mechanism across the semiconductor/semiconductor/metal junctions and the resultant activity enhancement are discussed. In parallel, recent successes in the theoretical modelling of semiconductor electronic structures at interfaces and how these explain the functionality of the junction structures is highlighted.

/pdf/visible-light-driven-heterojunction-photocatalysts-for-water-33q4busijg.pdf

Visible-light driven heterojunction photocatalysts for water splitting – a critical review

This paper describes the design and application of V2O5–MoO3/Al2O3 catalysts for the selective oxidation of methanol to dimethoxymethane (DMM). The V2O5–MoO3/Al2O3 catalysts exhibit superior performance for DMM yield than the corresponding samples with V and Mo species only, even at relativity low temperatures. The origin of high DMM yield of the V2O5–MoO3/Al2O3 catalysts is explored and attributed to the synergistic effect of V and Mo mixed oxides presented on the surface of the catalyst. The synergism can be ascribed to (i) the completion of a redox cycle and (ii) the enrichment of weak Bronsted acidic sites. The redox cycle of V O Mo oxides could be completed through electron transfer between lattice oxygen and metal cations. The V species exhibits a superior performance in the adsorption and activation of gaseous oxygen, as well as enhanced capability to restore the lattice oxygen and suppress the aggregation of Mo species. The enrichment of weak Bronsted acidic sites is attributed to the addition of MoO3 and the increase of partially reduced V and Mo species, respectively, which is critical to increasing the DMM yield. By adjusting the content of V2O5 and MoO3, we have obtained a 14V2O5–14MoO3/Al2O3 catalyst with the optimized amounts of redox sites and acidic sites, which exhibits a 54% methanol conversion with a DMM selectivity of 92% at 393 K.

Selective oxidation of methanol to dimethoxymethane on V2O5–MoO3/γ-Al2O3 catalysts

Highly-oriented Fe2O3/ZnFe2O4 nanocolumnar heterojunction with improved charge separation for photoelectrochemical water oxidation

Multifunctional TiO2 overlayer for p-Si/n-CdS heterojunction photocathode with improved efficiency and stability

Silicon-based (Si-based) junctions have been widely investigated in recent years as photoelectrochemical (PEC) water splitting photoelectrodes, including buried junctions and metal–insulator–semiconductor (MIS) Schottky junctions. However, Si-based MIS photoelectrodes suffer from low performance for the PEC oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) because of the dilemma that a thin insulator cannot provide enough interfacial passivation while a thick insulator will block the transport of charge carriers. Another trade-off is the fact that the photovoltage extracted from the band offset between the metal and semiconductor will be counteracted by the parasitic light absorption of the metal layer, sacrificing the saturation photocurrent. This paper describes the design and realization of a bifacial passivation strategy for the metal/Si interface of an MIS photoelectrode, featuring a bi-layer stack consisting of amorphous silicon (a-Si) for passivating the silicon surface and a metal oxide (TiO2) for passivating the metal surface. Upon the bifacial passivation of both a-Si and TiO2, the minority carrier lifetime of the Si MIS photoanode was significantly improved from 18 to 2360 μs. Enabled by this extremely long minority carrier lifetime, it becomes possible to place the MIS junction on the back side of a Si substrate to construct an inverted-MIS (I-MIS) structure to eliminate the parasitic light absorption of traditional Si MIS photoelectrodes. The obtained photoelectrode exhibits an excellent onset potential of 0.85 V and 0.62 V vs. reversible hydrogen electrode (RHE) for the OER and HER, respectively. Eventually, unprecedented applied bias photon-to-current efficiencies (ABPE) of 3.91% and 12.66% were obtained by Si MIS and Si I-MIS, which are the highest among MIS-based photoanodes and photocathodes, with 30 h and 108 h stable operation. When pairing the Si I-MIS photocathode with a BiVO4 photoanode to form a PEC membrane-free tandem cell, an unbiased solar-to-hydrogen conversion efficiency of 1.9% is achieved.

Bifacial passivation of n-silicon metal–insulator–semiconductor photoelectrodes for efficient oxygen and hydrogen evolution reactions

Most Bi-based photoelectrodes have suitable band gaps and can effectively promote the water oxidation reaction. However, simple preparation methods for Bi-based binary metal oxides as photoanodes are scarce. This paper describes a simple hydrothermal anion exchange method to synthesize Bi-based binary metal oxides with controlled morphologies. This synthesis process uses BiOI as the template and Bi source, which is eventually converted to Bi-based porous nanoflake photoanodes upon reaction with MOx (M = W, V, and Mo)-containing precursors. The photoanodes show well-shaped porous nanoflake morphologies and exhibit impressive photoelectrochemical properties compared to Bi-based photoanodes synthesized by conventional methods. These three samples possess long-term stability under solar irradiation and show considerable photocurrent for sulfite oxidation.

/pdf/fabrication-of-porous-nanoflake-bimox-m-w-v-and-mo-117kx6f9i7.pdf

Tuo Wang

Papers

Selective oxidation of methanol to dimethoxymethane on V2O5–MoO3/γ-Al2O3 catalysts

Highly-oriented Fe2O3/ZnFe2O4 nanocolumnar heterojunction with improved charge separation for photoelectrochemical water oxidation

Multifunctional TiO2 overlayer for p-Si/n-CdS heterojunction photocathode with improved efficiency and stability

Bifacial passivation of n-silicon metal–insulator–semiconductor photoelectrodes for efficient oxygen and hydrogen evolution reactions

Fabrication of porous nanoflake BiMOx (M = W, V, and Mo) photoanodes via hydrothermal anion exchange