A facile two-step electroreductive synthesis of anthraquinone/graphene nanocomposites as efficient electrocatalyst for O2 reduction in neutral medium

Metal-Free Graphene-Based Derivatives as Oxygen Reduction Reaction Electrocatalysts in Energy Conversion and Storage Systems: An Overview

Oxygen reduction reaction (ORR) is one of the most important reactions in electrochemical energy storage and conversion devices. To overcome the slow kinetics, minimize the overpotential, and make this reaction feasible, efficient, and stable, electrocatalysts are needed. Metal-free graphene-based systems are considered promising and cost-effective ORR catalysts with adjustable structures. This review is meant to give a rational overview of the graphene-based metal-free ORR electrocatalysts, illustrating the huge amount of related research developed particularly in the field of fuel cells and metal-air batteries, with particular attention to the synthesis procedures. The novelty of this review is that, beyond general aspects regarding the synthesis and characterization of graphene, above 90% of the various graphene (doped and undoped species, composites)-based ORR electrocatalysts have been reported, which represents an unprecedented thorough collection of both experimental and theoretical studies. Hundreds of references are included in the review; therefore, it can be considered as a vademecum in the field.

3D-Stretched Film Ni3 S2 Nanosheet/Macromolecule Anthraquinone Derivative Polymers for Electrocatalytic Overall Water Splitting

For the first time, a new polymer electrode AQS/S is prepared by compositing Ni₃ S₂ nanosheets and macromolecular anthraquinone derivative (AQD) supported on nickel foam with flying colors. The AQS/S exhibits high crystalline structure and abundant S defects. Density of state calculation shows that AQD has stable internal bonding and easy external bonding with metals, conducive to the dispersion of metal reaction sites, ensuring excellent activity and high stability. Under 1.0 m KOH solution, ultralow overpotentials of 62 and 133 mV at 10 mA cm^-2 on AQS/S for hydrogen evolution reaction and on activated AQS/S (A-AQS/S) for oxygen evolution reaction, respectively, are achieved. 100 h chronopotentiometry and the cyclic voltammetry tests show that catalysts have high durability. The AQS/S‖A-AQS/S two-electrode system is also found to have good electrocatalytic activity for 1.43 V to get 10 mA cm^-2  in overall water splitting, better than the state-of-the-art 20% Pt/C‖RuO₂ combination.

Modification of graphene on ultramicroelectrode array and its application in detection of dissolved oxygen

This paper investigated two different modification methods of graphene (GN) on ultramicroelectrode array (UMEA) and applied the GN modified UMEA for the determination of dissolved oxygen (DO). The UMEAs were fabricated by Micro Electro-Mechanical System (MEMS) technique and the radius of each ultramicroelectrode is 10 μm. GN-NH₂ and GN-COOH were modified on UMEA by using self-assembling method. Compared with GN-NH₂ modified UMEA, the GN-COOH modified UMEA showed better electrochemical reduction to DO, owing to better dispersing and more active sites. The GN-COOH on UMEA was electroreduced to reduced GN-COOH (rGN-COOH) to increase the conductivity and the catalysis performance. Finally, the palladium nanoparticles/rGN-COOH composite was incorporated into DO microsensor for the detection of DO.

Recent progress in graphene-based nanomaterials as advanced electrocatalysts towards oxygen reduction reaction

Development of state-of-the-art electrocatalysts with inexpensive and commercially available materials to facilitate sluggish cathodic oxygen reduction reaction (ORR) is a key issue in the development of fuel cells and other electrochemical energy devices. Although great progress has been achieved in this area of research and development, there are still some challenges in both their ORR activity and stability. The emergence of graphene (GN) provides an excellent alternative to electrode materials and great efforts have been made to utilize GN-based nanomaterials as promising electrode materials for ORR due to the high electrical conductivity, large specific surface area, profuse interlayer structure and abounding functional groups involved. It should be noted that rational design of these GN-based nanomaterials with well-defined morphology also plays an important role in their electrochemical performance for ORR. Considerable attempts were achieved to construct a variety of heteroatom doped GN nanomaterials or GN-based nanocomposites, aiming at fully using their excellent properties in their application in ORR. In this critical review, in line with the material design and engineering, some recent advancements in the development of GN-based electrocatalysts for ORR in electrochemical energy devices (fuel cells and batteries) are then highlighted, including heteroatom-doped GN nanomaterials, GN-based nonprecious hybrid nanocomposites (GN/metal oxides, GN/N-M, GN/carbon nitride, etc.) and GN/noble metal nanocomposites.