Yangyang Feng

Ultrathin Two-Dimensional Free-Standing Sandwiched NiFe/C for High-Efficiency Oxygen Evolution Reaction.

A NiFe-based compound is considered one of the most promising candidates for the highest oxygen evolution reaction (OER) electrocatalytic activities among all nonprecious metal-based electrocatalysts. In this report, a unique catalyst of free-standing sandwiched NiFe nanoparticles encapsulated by graphene sheets is first devised and fabricated. In this method, we use low-cost, sustainable, and environmentally friendly glucose as a carbon source, ultrathin Fe-doped Ni(OH)2 nanosheets as a precursor, and a sacrificial template. This special nanoarchitecture with a conductive network around active catalysts can accelerate electron transfer and prevent NiFe nanoparticles from aggregation and peeling off during long-time electrochemical reactions, thereby exhibiting an excellent OER activity and stability in basic solutions. In this work, our sandwiched catalyst presents well activities of a low onset of ∼1.44 V (vs RHE) and Tafel slope of ∼30 mV/decade in 1 M KOH at a scan rate of 5 mV/s.

Peapod‐Like Composite with Nickel Phosphide Nanoparticles Encapsulated in Carbon Fibers as Enhanced Anode for Li‐Ion Batteries

Herein, we introduce a peapod-like composite with Ni12 P5 nanoparticles encapsulated in carbon fibers as the enhanced anode in Li-ion batteries for the first time. In the synthesis, NiNH4 PO4 ⋅H2 O nanorods act as precursors and sacrificial templates, and glucose molecules serve as the green carbon source. With the aid of hydrogen bonding between the precursor and carbon source, a polymer layer is hydrothermally formed and then rationally converted into carbon fibers upon inert calcination at elevated temperatures. Meanwhile, NiNH4 PO4 ⋅H2 O nanorods simultaneously turn into Ni12 P5 nanoparticles encapsulated in carbon fibers by undergoing a decomposition and reduction process induced by high temperature and the carbon fibers. The obtained composite performs excellently as a Li-ion batteries anode relative to pure-phase materials. Specific capacity can reach 600 m Ah g(-1) over 200 cycles, which is much higher than that of isolated graphitized carbon or phosphides, and reasonably believed to originate from the synergistic effect based on the combination of Ni12 P5 nanoparticles and carbon fibers. Due to the benignity, sustainability, low cost, and abundance of raw materials of the peapod-like composite, numerous potential applications, in fields such as optoelectronics, electronics, specific catalysis, gas sensing, and biotechnology can be envisaged.

Designed synthesis of hollow Co3O4 nanoparticles encapsulated in a thin carbon nanosheet array for high and reversible lithium storage

The design and fabrication of novel composite nano-architectures is crucial for their applications in energy storage devices such as lithium ion batteries (LIBs). Herein, a thin carbon nanosheet array with encapsulated hollow Co3O4 nanoparticles is successfully fabricated on 3D Ni foam by using electrodeposited Co(OH)2 nanosheets as templates and followed by a two step annealing process. When used as an anode material in LIBs, the hollow Co3O4/carbon nanosheet composite displays an excellent performance with a high reversible capacity, excellent cycling stability and rate capability. This work is helpful for the design of an advanced electrode for LIBs, supercapacitors, electrochemical sensors, etc.

Unique Fe2P Nanoparticles Enveloped in Sandwichlike Graphited Carbon Sheets as Excellent Hydrogen Evolution Reaction Catalyst and Lithium-Ion Battery Anode.

The novel Fe2P nanoparticles encapsulated in sandwichlike graphited carbon envelope nanocomposite (Fe2P/GCS) that can be first applied in hydrogen evolution reaction (HER) as well as lithium-ion batteries (LIBs) has been designed and fabricated. The unique sandwiched Fe2P/GCS is characterized with several prominent merits, including large specific surface area, nanoporous structure, excellent electronic conductivity, enhanced structural integrity and so on. All of these endow the Fe2P/GCS with brilliant electrochemical performance. When used as a HER electrocatalyst in acidic media, the harvested Fe2P/GCS demonstrates low onset overpotential and Tafel slope as well as particularly outstanding durability. Moreover, as an anode material for LIBs, the sandwiched Fe2P/GCS presents high specific capacity and excellent cyclability and rate capability. As a consequence, the acquired Fe2P/GCS is a promising material for energy applications, especially HER and LIBs.

A General Strategy Towards Encapsulation of Nanoparticles in Sandwiched Graphene Sheets and the Synergic Effect on Energy Storage

A novel and universal approach towards the unique encapsulation of nanoparticles in the sandwiched graphene sheets is presented here. In the method, a low-cost, sustainable and environmentally friendly carbon source, glucose, is firstly applied to yield the high-quality, uniform and coupled graphene sheets in a large scale, and the pre-fabricated hydrated nanosheets act as the sacrificial templates to generate the enveloped metallic nanoparticles. After controllable oxidation or removal of the encapsulated nanoparticles, sandwiched nanocomposite with oxidizes nanoparticles encapsulated in graphene sheets or pure phase of sandwich-like and coupled graphene sheets would be achieved. Moreover, the synergic effect on energy storage via Li-ion batteries is solidly verified in the Co(3)O(4)@graphene nanocomposite. More importantly, the unique structure of the nanoparticles-encapsulated sandwiched graphene sheets will definitely result in additional applications, such as biosensors, supercapacitors and specific catalyses. These results have enriched the family of graphene-based materials and recognized some new graphene derivatives, which will be considerably meaningful in chemistry and materials sciences.

Novel peapod NiO nanoparticles encapsulated in carbon fibers for high-efficiency supercapacitors and lithium-ion batteries

Nickel oxide is regarded as one of the most promising electrodes in energy storage. In this report, a special peapod NiO/C is successfully designed and fabricated for the first time through a simple hydrothermal method by using green glucose as the carbon source. This unique structure can not only provide a large contact area between the electrolyte and active materials so as to promote fast ion and electron exchange, but also digest possible volume changes during long-time reactions so that it can lead to superior cyclic stability. Importantly, the porous structure can effectively accelerate ion diffusion, further enhancing the electrochemical performances. In this work, our peapod NiO/C exhibits excellent performances in both supercapacitors (SCs) and lithium-ion batteries (LIBs).

Monodisperse Sandwich-Like Coupled Quasi-Graphene Sheets Encapsulating Ni2P Nanoparticles for Enhanced Lithium-Ion Batteries

In this report, sandwiched Ni2 P nanoparticles encapsulated by graphene sheets are first synthesized by directly encapsulating functional units in graphene sheets instead of fabricating separate graphene sheets and then immobilizing the functional components onto the generated surfaces. In this strategy, we use low-cost, sustainable and environmentally friendly glucose as a carbon source and NiNH4 PO4 ⋅H2 O nanosheets as sacrificial templates. This unique structure obtained here cannot only prevent the nanoparticles from aggregation or loss but also enhance the electronic conductivity compared to the independent nanoparticles. Furthermore, the novel sandwich-like Ni2 P/C can be applied in plenty of fields, especially in electrical energy storage. In this paper, a series of electrochemical tests of the sandwich-like Ni2 P/C are carried out, which demonstrate the excellent cyclic stability and rate capacity for lithium-ion batteries.

Sandwich-like CoP/C nanocomposites as efficient and stable oxygen evolution catalysts

Nowadays, the sluggish kinetics of the oxygen evolution reaction (OER) has been a bottleneck factor in water electrolysis. Designing and synthesizing some materials, with novel and specific morphology, may hopefully relieve the present puzzle. Herein, a novel sandwich-like CoP/C nanocomposite was developed by a low-temperature phosphorization method using a carbon-encapsulated Co-based nanosheet as a precursor. The cross-section images directly show that the monodispersed CoP nanoparticles are sandwiched between two thin carbon layers. The outer coating of CoP nanoparticles serves as an efficient protective layer and conductive medium in the process of water electrolysis. Remarkably, the sandwich-like CoP/C obtains a small overpotential of only 330 mV (1.56 V vs. RHE) at a current density of 10 mA cm−2, which is favorably compared with the commercial IrO2/C (400 mV), sandwich-like CoO/C (450 mV) and macroporous CoP (610 mV) catalysts we prepared. This CoP/C nanocomposite also presents better stability in alkaline solution than that of CoO/C and macroporous CoP. What is important is that this excellent OER performance has exceeded most Co-based materials reported thus far. The sandwich-like CoP/C material we obtained affords the possibility of the pursuit of robust, low-cost and high-effective OER catalysts.

Quasi-graphene-envelope Fe-doped Ni2P sandwiched nanocomposites for enhanced water splitting and lithium storage performance

Developing advanced graphene-based composites is significant for the development of renewable green energy technology. Herein, we report a sandwich-like graphene-based composite (i.e., Fe-doped Ni2P nanoparticles encapsulated by a graphene-like envelope), which is synthesized by the first polymerization of glucose (as a green carbon source) on the Fe-doped NiNH4PO4·H2O nanosheet surface followed by high temperature annealing. The annealing process will crystallize the coated polymer into multilayer graphene, as the same time the Fe-doped precursor is decomposed into Fe-doped Ni2P ((Fe)Ni2P) nanoparticles encapsulated by the graphene envelope ((Fe)Ni2P/graphene). When evaluated as a water splitting catalyst in acidic solutions, the graphene-encapsulated Fe-doped Ni2P exhibits a low overpotential (∼50 mV) and a small Tafel slope (∼45 mV per decade) in 0.5 M H2SO4 solution. More importantly, the (Fe)Ni2P/graphene composite shows an excellent stability in acid solutions in contrast to conventional Ni-based catalysts. On the other hand, owing to the structural advantage (i.e., efficient inner volume space for the nanoparticle expansion, high porosity for the electrolyte diffusion and high conductivity), the (Fe)Ni2P/graphene nanocomposite exhibits a high specific capacity of 642 mA h g−1 at 0.2 C and excellent cycling stability (93% retained after 200 cycles).

Designed Synthesis of Transition Metal/Oxide Hierarchical Peapods Array with the Superior Lithium Storage Performance

In this report, a novel hierarchical peapoded array with Co3O4 nanoparticles encapsulated in graphitized carbon fiber is introduced for the first time. The unique peapoded structure is suitable for the excellent anode in LIBs and demonstrates enhanced rate capability, cyclability and prolonged lifespan, e.g. the specific capacity can reach up to 1150 mAh/g. All the enhanced electrochemical performance is reasonably derived from the peapod-like and aligned conformation. Furthermore, due to the specialty of the structure and the versatility of Co3O4, the composite will find more applications in specific catalysis, biomedicine, electronics, optoelectronic engineering and gas sensing. The fabrication strategy developed here is also a rational and universal approach towards peapod-like architecture and has significantly widened the specific functional material domain we created before. In our design, more peapod-like aligned samples with various nanoparticles, e.g. oxides, phosphides, even nitrides, encapsulated in graphitized carbon fibers, have been lifted on the research agenda and the results will be presented soon.