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

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

Ionic liquids (ILs) are liquids consisting entirely of ions and can be further defined as molten salts having melting points lower than 100 °C. One of the most important research areas for IL utilization is undoubtedly their energy application, especially for energy storage and conversion materials and devices, because there is a continuously increasing demand for clean and sustainable energy. In this article, various application of ILs are reviewed by focusing on their use as electrolyte materials for Li/Na ion batteries, Li-sulfur batteries, Li-oxygen batteries, and nonhumidified fuel cells and as carbon precursors for electrode catalysts of fuel cells and electrode materials for batteries and supercapacitors. Due to their characteristic properties such as nonvolatility, high thermal stability, and high ionic conductivity, ILs appear to meet the rigorous demands/criteria of these various applications. However, for further development, specific applications for which these characteristic properties becom...

Application of Ionic Liquids to Energy Storage and Conversion Materials and Devices

Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR.

Earth-Abundant Nanomaterials for Oxygen Reduction.

Ratiometric fluorescence sensor for organophosphorus pesticide detection based on opposite responses of two fluorescence reagents to MnO2 nanosheets.

Titanium dioxide and polypyrrole molecularly imprinted polymer nanocomposites based electrochemical sensor for highly selective detection of p-nonylphenol.

Compared with optical density variations, human eyes are more sensitive to color variations. Herein, we develop a multicolor biosensor for organophosphorus pesticides (OPs) detection based on the enzymatic etching of gold nanorods (AuNRs). In the presence of acetylcholinesterase (AChE) and choline oxidase (CHO), the substrate acetylcholine (ACh) is catalyzed to generate H2O2. The resultant H2O2 etches AuNRs and lead to the etching of AuNRs, accompanying with distinct color changes. OPs inhibit the activity of AChE, which prevent the generation of H2O2 and the etching of AuNRs. Visual semi-quantitative determination of OPs is significantly improved due to multiple colors are presented in this biosensor. LSPR shift (ΔW), after and before inhibition, was utilized to quantitatively measure OPs. Under optimum conditions, the LSPR band shift of AuNRs are linearly dependent on the logarithm of inhibitor concentration over the ranges from 0.01 to 50 μg/L and from 1.0 to 500 μg/L, for dichlorvos and demeton, respectively. LOD are much lower than the maximum residue limits specified in the U.S Department of Agriculture and European Union pesticide regulations. They are also lower than those obtained by previously reported colorimetric methods.

Multicolor sensor for organophosphorus pesticides determination based on the bi-enzyme catalytic etching of gold nanorods

The development of efficient and low-cost non-precious-metal electrocatalysts such as Fe–N/C for the oxygen reduction reaction (ORR) is crucial for fuel cells and metal–air batteries. Here, we report a class of highly efficient Fe–N/C electrocatalysts derived from versatile imidazolium-based ionic liquids (ILs) with a halogen-coordinated iron anion. Without any supports, templates, or multi-step pyrolysis, the as-prepared Fe–N/C catalysts exhibited superior activity in the ORR to the state-of-the-art Pt/C in alkaline electrolytes by 44 mV in half-wave potential. More interestingly, owing to the versatile configuration of the imidazolium-based IL precursors, a diverse range of catalyst structures was successfully modulated. Based on this, it was clearly revealed that the electrical conductivity, type/amount of N dopants, and “effective porosity” (not the conventional total surface area) jointly determined the electrocatalytic activity. A pivotal radar chart is further proposed to successfully predict activity in the ORR merely from the structures of Fe–N/C catalysts. The proposed ILs platform would provide a valuable toolbox for the molecular design of precursors to tune the structures of Fe–N/C electrocatalysts towards excellent activity in the ORR in a highly flexible manner, and facilitate the long-term challenging study of relationships between processing, structure and activity.

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Ionic liquid-derived Fe–N/C catalysts for highly efficient oxygen reduction reaction without any supports, templates, or multi-step pyrolysis

We report a general method for the fabrication of three-dimensional (3D) macroporous graphene/conducting polymer modified electrode and nitrogen-doped graphene modified electrode. This method involves three consecutive steps. First, the 3D macroporous graphene (3D MG) electrode was fabricated electrochemically by reducing graphene oxide dispersion on different conducting substrates and used hydrogen bubbles as the dynamic template. The morphology and pore size of 3D MG could be governed by the use of surfactants and the dynamics of bubble generation and departure. Second, 3D macroporous graphene/polypyrrole (MGPPy) composites were constructed via directly electropolymerizing pyrrole monomer onto the networks of 3D MG. Due to the benefit of the good conductivity of 3D MG and pseudocapacitance of PPy, the composites manifest outstanding area specific capacitance of 196 mF cm–2 at a current density of 1 mA cm–2. The symmetric supercapacitor device assembled by the composite materials had a good capacity prop...

Three-Dimensional Macroporous Polypyrrole-Derived Graphene Electrode Prepared by the Hydrogen Bubble Dynamic Template for Supercapacitors and Metal-Free Catalysts.

Anran Liu

Papers

Ratiometric fluorescence sensor for organophosphorus pesticide detection based on opposite responses of two fluorescence reagents to MnO2 nanosheets.

Titanium dioxide and polypyrrole molecularly imprinted polymer nanocomposites based electrochemical sensor for highly selective detection of p-nonylphenol.

Multicolor sensor for organophosphorus pesticides determination based on the bi-enzyme catalytic etching of gold nanorods

Ionic liquid-derived Fe–N/C catalysts for highly efficient oxygen reduction reaction without any supports, templates, or multi-step pyrolysis

Three-Dimensional Macroporous Polypyrrole-Derived Graphene Electrode Prepared by the Hydrogen Bubble Dynamic Template for Supercapacitors and Metal-Free Catalysts.