and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

Over the past few decades, the design and development of advanced electrocatalysts for efficient energy conversion technologies have been subjects of extensive study. With the discovery of graphene, two-dimensional (2D) nanomaterials have emerged as some of the most promising candidates for heterogeneous electrocatalysts due to their unique physical, chemical, and electronic properties. Here, we review 2D-nanomaterial-based electrocatalysts for selected electrocatalytic processes. We first discuss the unique advances in 2D electrocatalysts based on different compositions and functions followed by specific design principles. Following this overview, we discuss various 2D electrocatalysts for electrocatalytic processes involved in the water cycle, carbon cycle, and nitrogen cycle from their fundamental conception to their functional application. We place a significant emphasis on different engineering strategies for 2D nanomaterials and the influence these strategies have on intrinsic material performance, ...

Emerging Two-Dimensional Nanomaterials for Electrocatalysis

Lithium-sulfur (Li-S) batteries have attracted tremendous interest because of their high theoretical energy density and cost effectiveness. The target of Li-S battery research is to produce batteries with a high useful energy density that at least outperforms state-of-the-art lithium-ion batteries. However, due to an intrinsic gap between fundamental research and practical applications, the outstanding electrochemical results obtained in most Li-S battery studies indeed correspond to low useful energy densities and are not really suitable for practical requirements. The Li-S battery is a complex device and its useful energy density is determined by a number of design parameters, most of which are often ignored, leading to the failure to meet commercial requirements. The purpose of this review is to discuss how to pave the way for reliable Li-S batteries. First, the current research status of Li-S batteries is briefly reviewed based on statistical information obtained from literature. This includes an analysis of how the various parameters influence the useful energy density and a summary of existing problems in the current Li-S battery research. Possible solutions and some concerns regarding the construction of reliable Li-S batteries are comprehensively discussed. Finally, insights are offered on the future directions and prospects in Li-S battery field.

More Reliable Lithium-Sulfur Batteries: Status, Solutions and Prospects.

Oxygen electrocatalysis, including the oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER), is a critical process for metal-air batteries Therefore, the development of electrocatalysts for the OER and the ORR is of essential importance Indeed, various advanced electrocatalysts have been designed for the ORR or the OER; however, the origin of the advanced activity of oxygen electrocatalysts is still somewhat controversial The enhanced activity is usually attributed to the high surface areas, the unique facet structures, the enhanced conductivities, or even to unclear synergistic effects, but the importance of the defects, especially the intrinsic defects, is often neglected More recently, the important role of defects in oxygen electrocatalysis has been demonstrated by several groups To make the defect effect clearer, the recent development of this concept is reviewed here and a novel principle for the design of oxygen electrocatalysts is proposed An overview of the defects in carbon-based, metal-free electrocatalysts for ORR and various defects in metal oxides/selenides for OER is also provided The types of defects and controllable strategies to generate defects in electrocatalysts are presented, along with techniques to identify the defects The defect-activity relationship is also explored by theoretical methods

Defect Chemistry of Nonprecious-Metal Electrocatalysts for Oxygen Reactions

To meet the growing energy demands in a low-carbon economy, the development of new materials that improve the efficiency of energy conversion and storage systems is essential. Mesoporous materials offer opportunities in energy conversion and storage applications owing to their extraordinarily high surface areas and large pore volumes. These properties may improve the performance of materials in terms of energy and power density, lifetime and stability. In this Review, we summarize the primary methods for preparing mesoporous materials and discuss their applications as electrodes and/or catalysts in solar cells, solar fuel production, rechargeable batteries, supercapacitors and fuel cells. Finally, we outline the research and development challenges of mesoporous materials that need to be overcome to increase their contribution in renewable energy applications. Mesoporous materials are finding increasing uses in energy conversion and storage devices. This Review highlights recent developments in the synthesis of mesoporous materials and their applications as electrodes and/or catalysts in solar cells, solar fuel production, rechargeable batteries, supercapacitors and fuel cells.

Mesoporous materials for energy conversion and storage devices

Architecture of graphdiyne nanoscale films

Sulfur is a promising cathode material for lithium-sulfur batteries because of its high theoretical capacity (1,675 mA h g(-1)); however, its low electrical conductivity and the instability of sulfur-based electrodes limit its practical application. Here we report a facile in situ method for preparing three-dimensional porous graphitic carbon composites containing sulfur nanoparticles (3D S@PGC). With this strategy, the sulfur content of the composites can be tuned to a high level (up to 90 wt%). Because of the high sulfur content, the nanoscale distribution of the sulfur particles, and the covalent bonding between the sulfur and the PGC, the developed 3D S@PGC cathodes exhibit excellent performance, with a high sulfur utilization, high specific capacity (1,382, 1,242 and 1,115 mA h g(-1) at 0.5, 1 and 2 C, respectively), long cycling life (small capacity decay of 0.039% per cycle over 1,000 cycles at 2 C) and excellent rate capability at a high charge/discharge current.

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Three-dimensional porous carbon composites containing high sulfur nanoparticle content for high-performance lithium–sulfur batteries

The cycle life and energy density of rechargeable metal batteries are largely limited by the dendritic growth of their metal anodes (lithium, sodium or zinc). Here we develop a three-dimensional cross-linked polyethylenimine lithium-ion-affinity sponge as the lithium metal anode host to mitigate the problem. We show that electrokinetic surface conduction and electro-osmosis within the high-zeta-potential sponge change the concentration and current density profiles, which enables dendrite-free plating/stripping of lithium with a high Coulombic efficiency at high deposition capacities and current densities, even at low temperatures. The use of a lithium-hosting sponge leads to a significantly improved cycling stability of lithium metal batteries with a limited amount of lithium (for example, the areal lithium ratio of negative to positive electrodes is 0.6) at a commercial-level areal capacity. We also observed dendrite-free morphology in sodium and zinc anodes, which indicates a broader promise of this approach. Metallic dendrite growth of metal anodes is a major concern in developing next-generation metal-ion batteries. Here the authors develop a cross-linked polyethylenimine as a metal host that enables electrokinetic effects for uniform metal deposition.

Stable metal battery anodes enabled by polyethylenimine sponge hosts by way of electrokinetic effects

Graphdiyne nanotube (GDNT) arrays were prepared through an anodic aluminum oxide template catalyzed by Cu foil. The as-grown nanotubes have a smooth surface with a wall thickness of about 40 nm; after annealing, the GDNTs are about 15 nm. The morphology-dependent field emission properties of graphdiyne arrays were measured and display high performance field emission properties. The turn-on field and threshold field of GDNTs annealed decreased to 4.20 and 8.83 V/μm, respectively.

Construction of Tubular Molecule Aggregations of Graphdiyne for Highly Efficient Field Emission

Lithium metal is a promising anode candidate for the next-generation rechargeable battery due to its highest specific capacity (3860 mA h g−1) and lowest potential, but low Coulombic efficiency and formation of lithium dendrites hinder its practical application. Here, we report a self-formed flexible hybrid solid-electrolyte interphase layer through co-deposition of organosulfides/organopolysulfides and inorganic lithium salts using sulfur-containing polymers as an additive in the electrolyte. The organosulfides/organopolysulfides serve as “plasticizer” in the solid-electrolyte interphase layer to improve its mechanical flexibility and toughness. The as-formed robust solid-electrolyte interphase layers enable dendrite-free lithium deposition and significantly improve Coulombic efficiency (99% over 400 cycles at a current density of 2 mA cm−2). A lithium-sulfur battery based on this strategy exhibits long cycling life (1000 cycles) and good capacity retention. This study reveals an avenue to effectively fabricate stable solid-electrolyte interphase layer for solving the issues associated with lithium metal anodes. The practical application of lithium metal anodes suffers from the poor Coulombic efficiency and growth of lithium dendrites. Here, the authors report an approach to enable the self-formation of stable and flexible solid-electrolyte interphase layers which serve to address both issues.

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Guoxing Li

Papers

Architecture of graphdiyne nanoscale films

Three-dimensional porous carbon composites containing high sulfur nanoparticle content for high-performance lithium–sulfur batteries

Stable metal battery anodes enabled by polyethylenimine sponge hosts by way of electrokinetic effects

Construction of Tubular Molecule Aggregations of Graphdiyne for Highly Efficient Field Emission

Organosulfide-plasticized solid-electrolyte interphase layer enables stable lithium metal anodes for long-cycle lithium-sulfur batteries