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?

A review on g-C3N4-based photocatalysts

Increasing demand for finding eco-friendly and everlasting energy sources is now totally depending on fuel cell technology. Though it is an eco-friendly way of producing energy for the urgent requirements, it needs to be improved to make it cheaper and more eco-friendly. Although there are several types of fuel cells, the hydrogen (H2) and oxygen (O2) fuel cell is the one with zero carbon emission and water as the only byproduct. However, supplying fuels in the purest form (at least the H2) is essential to ensure higher life cycles and less decay in cell efficiency. The current large-scale H2 production is largely dependent on steam reforming of fossil fuels, which generates CO2 along with H2 and the source of which is going to be depleted. As an alternate, electrolysis of water has been given greater attention than the steam reforming. The reasons are as follows: the very high purity of the H2 produced, the abundant source, no need for high-temperature, high-pressure reactors, and so on. In earlier days,...

Recent Trends and Perspectives in Electrochemical Water Splitting with an Emphasis on Sulfide, Selenide, and Phosphide Catalysts of Fe, Co, and Ni: A Review

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

Solvothermal synthesis and characterization of sandwich-like graphene/ZnO nanocomposites

One-pot solvothermal preparation of magnetic reduced graphene oxide-ferrite hybrids for organic dye removal

Herein we demonstrate a facile and general process for fabricating P25/silver orthophosphate/graphene oxide (P25/Ag 3 PO 4 /GO) ternary composite materials using electrostatically-driven assembly and ion-exchange method. The composite materials reveal a well-defined heterostructure where few-layer GO sheets are decorated with microsized Ag 3 PO 4 particles and TiO 2 nanoparticles. The photodegradation of dye molecule and inactivation of bacteria can be tuned by varying the added amount of GO and the molar ratio of Ag 3 PO 4 /P25. The photocatalytic activity for degrading organic dye molecule and bactericidal performance could be improved by synergistic effects derived from the P25/Ag 3 PO 4 /GO heterostructure. A detailed analysis of the reactions mechanism by radical-capture agents suggests photo-induced active holes and reactive oxygen species (ROS) are responsible for the enhanced photocatalytic degradation activity owing to effective visible light harvesting, improved separation efficiency and fast interfacial charge transfer. Intrinsic antibacterial activity of dissolved Ag + ions is also considered to play an important role in determining the excellent bactericidal performance of the P25/Ag 3 PO 4 /GO ternary composite. We believe that this work provides new insights into the low-cost, large-scale production of multifunctional composite materials for the applications in solar photocatalytic degradation of harmful volatile organic compounds (VOCs) and common pathogenic bacteria in wastewater.

Fabrication of P25/Ag3PO4/graphene oxide heterostructures for enhanced solar photocatalytic degradation of organic pollutants and bacteria

Solar-driven water oxidation is the key step for overall water splitting that efficiently harvests and converts solar energy into fuels; the development of a highly efficient photocatalyst that can mediate water oxidation has become an appealing challenge. Herein, we report a facile two-step process to decorate silver phosphate (Ag3PO4) particles on different types of graphitic carbon nitrides (g-C3N4) as composite photocatalysts for water oxidation. For all the Ag3PO4/g-C3N4 materials, an in situ Z-scheme is created by the generation of Ag nanoparticles which act as a cross-linking bridge between Ag3PO4 and g-C3N4 in the composite, resulting in better charge separation and higher catalytic performance. A detailed analysis emphasizes the importance of the g-C3N4 on the chemical, photophysical, and catalytic properties of the composite materials. Our results show that the alteration of the morphology dominates the performance of the composite materials.

Tuning the morphology of g-C3N4 for improvement of Z-scheme photocatalytic water oxidation

A novel composite with CoP nanoparticles uniformly deposited on reduced graphene oxide (RGO) sheets is prepared through a facile two-step approach. The as-prepared CoP/RGO composite is investigated as an electrocatalyst for the hydrogen evolution reaction (HER). It is found that the CoP/RGO composite shows an enhanced catalytic activity with a smaller Tafel slope (104.8 mV per decade), a much larger exchange current density (4.0 × 10−5 A cm−2) and lower estimated HER activation energy (41.4 kJ mol−1) than pure CoP. Besides, the CoP/RGO composite exhibits good stability in acidic solution, the HER catalytic activity of which shows no obvious degradation after 500 cycles. Such enhanced catalytic activity stems from the abundance of active catalytic sites, the increased electrochemically accessible surface area and significantly improved electrochemical conductivity of the CoP/RGO composite. The good catalytic activity demonstrates that the CoP/RGO composite could be a promising electrocatalyst in hydrogen production.

Kangmin Chen

Papers

Solvothermal synthesis and characterization of sandwich-like graphene/ZnO nanocomposites

One-pot solvothermal preparation of magnetic reduced graphene oxide-ferrite hybrids for organic dye removal

Fabrication of P25/Ag3PO4/graphene oxide heterostructures for enhanced solar photocatalytic degradation of organic pollutants and bacteria

Tuning the morphology of g-C3N4 for improvement of Z-scheme photocatalytic water oxidation

CoP nanoparticles deposited on reduced graphene oxide sheets as an active electrocatalyst for the hydrogen evolution reaction