Energy storage devices that can deliver high powers have many applications, including hybrid vehicles and renewable energy. Much research has focused on increasing the power output of lithium batteries by reducing lithium-ion diffusion distances, but outputs remain far below those of electrochemical capacitors and below the levels required for many applications. Here, we report an alternative approach based on the redox reactions of functional groups on the surfaces of carbon nanotubes. Layer-by-layer techniques are used to assemble an electrode that consists of additive-free, densely packed and functionalized multiwalled carbon nanotubes. The electrode, which is several micrometres thick, can store lithium up to a reversible gravimetric capacity of approximately 200 mA h g(-1)(electrode) while also delivering 100 kW kg(electrode)(-1) of power and providing lifetimes in excess of thousands of cycles, both of which are comparable to electrochemical capacitor electrodes. A device using the nanotube electrode as the positive electrode and lithium titanium oxide as a negative electrode had a gravimetric energy approximately 5 times higher than conventional electrochemical capacitors and power delivery approximately 10 times higher than conventional lithium-ion batteries.

High-Power Lithium Batteries from Functionalized Carbon Nanotube Electrodes

Phosphorus compounds, such as metal phosphides and phosphates have shown excellent performances and great potential in electrochemical energy storage, which are demonstrated by research works published in recent years. Some of these metal phosphides and phosphates and their hybrids compare favorably with transition metal oxides/hydroxides, which have been studied extensively as a class of electrode materials for supercapacitor applications, where they have limitations in terms of electrical and ion conductivity and device stability. To be specific, metal phosphides have both metalloid characteristics and good electric conductivity. For metal phosphates, the open-framework structures with large channels and cavities endow them with good ion conductivity and charge storage capacity. In this review, we present the recent progress on metal phosphides and phosphates, by focusing on their advantages/disadvantages and potential applications as a new class of electrode materials in supercapacitors. The synthesis methods to prepare these metal phosphides/phosphates are looked into, together with the scientific insights involved, as they strongly affect the electrochemical energy storage performance. Particular attentions are paid to those hybrid-type materials, where strong synergistic effects exist. In the summary, the future perspectives and challenges for the metal phosphides, phosphates and hybrid-types are proposed and discussed.

Metal Phosphides and Phosphates-based Electrodes for Electrochemical Supercapacitors.

The significance of graphene and its two-dimensional (2D) analogous inorganic layered materials especially as hexagonal boron nitride (h-BN) and molybdenum disulphide (MoS2) for “clean energy” applications became apparent over the last few years due to their extraordinary properties. In this review article we study the current progress and selected challenges in the syntheses of graphene, h-BN and MoS2 including energy storage applications as supercapacitors and batteries. Various substrates/catalysts (metals/insulator/semiconducting) have been used to obtain graphene, h-BN and MoS2 using different kinds of precursors. The most widespread methods for synthesis of graphene, h-BN and MoS2 layers are chemical vapor deposition (CVD), plasma-enhanced CVD, hydro/solvothermal methods, liquid phase exfoliation, physical methods etc. Current research has shown that graphene, h-BN and MoS2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries. This review article also contains the discussion on the opportunities and perspectives of these materials (graphene, h-BN and MoS2) in the energy storage fields. We expect that this written review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene, h-BN and MoS2 layers based materials.

A review on synthesis of graphene, h-BN and MoS 2 for energy storage applications: Recent progress and perspectives

A cost-effective and highly efficient oxygen evolution reaction (OER) electrocatalyst will be significant for the future energy scenario. The emergence of the core-shell heterostructure has invoked new feasibilities to inspire the full potential of non-precious-metal candidates. The shells always have a large thickness, affording robust mechanical properties under harsh reaction conditions, which limits the full exposure of active sites with highly intrinsic reactivity and extrinsic physicochemical characters for optimal performance. Herein, a nanosized CoNi hydroxide@hydroxysulfide core-shell heterostructure is fabricated via an ethanol-modified surface sulfurization method. Such a synthetic strategy is demonstrated to be effective in controllably fabricating a core-shell heterostructure with an ultrathin shell (4 nm) and favorable exposure of active sites, resulting in a moderately regulated electronic structure, remarkably facilitated charge transfer, fully exposed active sites, and a strongly coupled heterointerface for energy electrocatalysis. Consequently, the as-obtained hydroxide@hydroxysulfide core-shell is revealed as a superior OER catalyst, with a small overpotential of 274.0 mV required for 10.0 mA cm-2 , a low Tafel slope of 45.0 mV dec-1 , and a favorable long-term stability in 0.10 M KOH. This work affords fresh concepts and strategies for the design and fabrication of advanced core-shell heterostructures, and thus opens up new avenues for the targeted development of high-performance energy materials.

A Nanosized CoNi Hydroxide@Hydroxysulfide Core-Shell Heterostructure for Enhanced Oxygen Evolution.

The conversion of renewable biomass offers a great opportunity for economic fabrication of carbon materials for energy storage devices. However, it is difficult to finely tune the structures of biomass-derived hard carbons (BHCs) due to the inherent robust microstructures of biomass itself, limiting the wide applications of BHCs. Obtaining routes to further optimize the structures of BHCs for supercapacitors is still a large challenge. Inspired by nature in which leaves effectively increase the air-accessible surface area of plants to absorb more carbon dioxide for photosynthesis, we aim to increase the accessible surface area of BHCs for ion adsorption by grafting leaf-like units onto the surface of BHCs. In this study, porous carbon nanosheets (PCNSs) functioning as porous leaves are grafted onto rice husk-derived carbons (RHCs) to fabricate PCNS/RHC composites. The as-prepared PCNS/RHC composites are endowed with sheet-like architecture and abundant short pores. As the electrodes for supercapacitors, the PCNS/RHC composite exhibits a high specific capacitance of 315 F g−1 at 0.1 A g−1 and an excellent rate capability of 189 F g−1 at 50 A g−1. The present study demonstrates an effective and universal strategy to boost the functionality of BHCs materials for energy storage devices.

Surface modification of biomass-derived hard carbon by grafting porous carbon nanosheets for high-performance supercapacitors

Boosting H 2 Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

The production of functionalized anilines by chemoselective hydrogenation of nitroarenes occupies an important position in the chemical industries. Recently, cobalt and nitrogen codoped carbon (Co–...

Origin of the Activity of Co–N–C Catalysts for Chemoselective Hydrogenation of Nitroarenes

The increasing need for clean and sustainable energy inspires researchers to explore low-cost nonprecious metal electrocatalysts for advanced energy storage and conversion. Herein, we develop a rea...

Reactive Template-Derived CoFe/N-Doped Carbon Nanosheetsas Highly Efficient Electrocatalysts toward Oxygen Reduction, OxygenEvolution, and Hydrogen Evolution

Heteroatom doping is a very important approach to improve the performances of carbon-based electrode materials applied in the energy storage and conversion field. Herein, a strategy based on the design of faradaic redox active sites has been developed to synthesize nitrogen and oxygen co-doped carbon foam with a hierarchical porous structure. By a facile two-step method of incipient impregnation and carbonization, the quinone-amine polymer (PAQ) precursor can be in situ polymerized and carbonized on the surface of a nanosized MgO template to obtain carbon foam after removal of MgO with acetic acid. The obtained carbon foam possesses a high content of heteroatoms (total 12.26 at%) as well as faradaic active sites including nitrogen- and oxygen-containing functional groups, which not only enhance the wettability of the electrode material surface to electrolyte but also impart high pseudo-capacitance to the carbon-based skeleton. In addition, the hierarchical micro–meso–macro porous structure provides a large specific surface area (1215 m2 g−1) and a mediated pathway for electrolyte ion diffusion. Serving as a symmetric supercapacitor electrode material in aqueous electrolyte, the co-doped carbon foam yields excellent performance, delivering a high specific capacitance of 321 F g−1 at 1 A g−1, a superior energy density of 15.91 W h kg−1 at a power density of 0.4 kW kg−1, and excellent long-term stability, retaining 98% of its initial capacitance after 15 000 cycles at 5 A g−1.

In situ formation/carbonization of quinone-amine polymers towards hierarchical porous carbon foam with high faradaic activity for energy storage

Developing earth-abundant, highly active, and durable electrocatalysts for the oxygen evolution reaction (OER) is very important for many renewable energy conversion processes. Herein, we report a novel OER electrocatalyst of NiCo layered double hydroxide@NiCo-hydroxysulfide (NiCo-LDH@HOS) nanosheet arrays, which are prepared by a rapid room-temperature sulfurization of the surface of NiCo-LDH nanosheets grown on Ni foam. The surface sulfurization exerts important influences/changes on the structure, composition, surface properties and chemistry of NiCo-LDH. After surface sulfurization, the resulted NiCo-hydroxysulfide layer armor improved electrical conductivity and chemical resistance to alkaline electrolyte, delivers a stable current density of 10.0 mA cm–2 at a low overpotential of 293 mV in 0.1 M KOH solution, maintaining high stability during a 62 h test. The achieved enhanced oxygen evolution activity and improved durability are superior to those of NiCo-LDH nanosheets and benchmark commercial RuO2...

Shanyong Chen

Papers

Boosting H 2 Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

Origin of the Activity of Co–N–C Catalysts for Chemoselective Hydrogenation of Nitroarenes

Reactive Template-Derived CoFe/N-Doped Carbon Nanosheetsas Highly Efficient Electrocatalysts toward Oxygen Reduction, OxygenEvolution, and Hydrogen Evolution

In situ formation/carbonization of quinone-amine polymers towards hierarchical porous carbon foam with high faradaic activity for energy storage

Surface Sulfurization of NiCo-Layered Double Hydroxide Nanosheets Enable Superior and Durable Oxygen Evolution Electrocatalysis