Shuyan Gao

Transforming organic-rich amaranthus waste into nitrogen-doped carbon with superior performance of the oxygen reduction reaction

We present a cost-effective approach to dispose of amaranthus waste (the discarded leaves and stalks of amaranthus and the extract remains of natural amaranthus red) to yield nitrogen-doped carbon. Amaranthus waste is a natural, abundantly available, and yearly renewable source, acting as a single precursor for nitrogen (mainly from the lysine-rich amino acids) as well as carbon. It therefore eliminates the need for multiple hazardous chemicals including organic precursors for similar synthesis processes. Our facile experimental strategy without any activation supports reasonable nitrogen doping in porous carbon along with a high surface area and excellent conductivity, which leads to a superior electrocatalytic oxygen reduction activity and proves to be a promising alternative for costly Pt-based electrocatalysts in fuel cells in terms of excellent electrocatalytic performance, high selectivity, and long durability. This judicious transformation of organic-rich waste not only addresses the disposal issue, but also generates valuable functional carbon materials from the discard. Our as-synthesized carbon will certainly be believed to be a trend setter and have greater economic ramifications by creating value-added materials from waste.

Large scale production of biomass-derived N-doped porous carbon spheres for oxygen reduction and supercapacitors

The urgent need for sustainable energy development depends on the progress of green technologies, which have steered hot research areas into environmentally benign approaches via inexpensive precursors and abundant resources obtained directly from nature for energy devices such as fuel cells and supercapacitors. By using fermented rice as starting materials, we herein demonstrate a facile, green and scalable approach to synthesize porous N-doped carbon spheres characterised by high specific surface areas (2105.9 m2 g−1) and high porosity (1.14 cm3 g−1), which exhibit not only excellent electrocatalytic activity toward the four-electron oxygen reduction reaction with long-term stability for fuel cells, but also have excellent resistance to crossover effects and CO poisoning superior to that of the commercial Pt/C catalyst. Furthermore, the naturally derived porous N-doped carbon spheres, used as the active electrode materials, present superior performance for capacitors with a capacitance of 219 F g−1 at a high discharge current density of 15 A g−1 and good cycling stability for over 4400 cycles. This work shows a good example for taking advantage of the abundant resources provided by nature, and opening the door for the creation of functional materials with promising applications in high-performance renewable devices related to energy conversion and storage.

A green one-arrow-two-hawks strategy for nitrogen-doped carbon dots as fluorescent ink and oxygen reduction electrocatalysts

A green strategy has been developed for synthesizing nitrogen-doped carbon dots (N-CDs) via hydrothermal treatment of willow leaves. The supernatant exhibits strong blue fluorescence under UV radiation and can be directly used as a fluorescent ink, while the solid product with pyrolysis possesses excellent electrocatalytic activity for a highly efficient oxygen reduction reaction with great stability and methanol/CO tolerance superior to a commercial Pt/C catalyst.

Peanut-Shell-like Porous Carbon from Nitrogen-Containing Poly-N-phenylethanolamine for High-Performance Supercapacitor

An efficient soft-template method is proposed for the synthesis of peanut shell-like porous carbon as high-performance supercapacitor electrode materials. The procedure is based on the pyrolysis and chemical activation processes using N-phenylethanolamine as precursor and KOH as activation agent. In a three-electrode system, the resultant carbon material has a specific capacitance of 356 F g(-1) at 1 A g(-1) and a good stability over 1000 cycles. Besides, at a high current density of 30 A g(-1), it has a specific capacitance of 249 F g(-1) and maintains 96% after 10,000 cycles. In two-electrode cell configuration, it delivers about 21.53 Wh kg(-1) at a current density of 20 A g(-1), which is about 7 times higher than the commercial device (<3 Wh kg(-1)). Both high specific capacitance and excellent cycling stabilities guarantee its utilization in supercapacitors.

Nitrogen-enriched carbon from bamboo fungus with superior oxygen reduction reaction activity

Fuel cells are promising candidates for clean and high-efficient energy conversion in the future. The development of carbon-based inexpensive metal-free ORR catalysts has become one of the most attractive topics in the fuel cell field. Herein, we report a N-doped carbon catalyst with a surface area of up to 1895.5 m2 g−1 using a natural product (bamboo fungus) as the starting material. In 0.1 M KOH electrolyte, the ORR onset potential for the catalyst is high up to 0.089 V vs. Ag/AgCl. Moreover, it shows superior stability, fuel crossover resistance, and selective activity to a commercial Pt/C catalyst. In addition, the sample displays excellent stability, i.e. no obvious decrease in current was observed after 1000 continuous cycles between −0.7 and 0.3 V in O2-saturated 0.1 M KOH. Moreover, both the structural characterizations and electrochemical tests verify that the treatment techniques of biomass have an important impact on the materials.

Biomolecule-assisted in situ route toward 3D superhydrophilic Ag/CuO micro/nanostructures with excellent artificial sunlight self-cleaning performance

Three-dimensionally (3D) hierarchical micro/nano oriented arrays constructed from nanometer-sized building blocks represent an important group of materials and have received enormous attention for a series of applications because they can offer both the advantages of nanosized building blocks and micro- or submicrometer-sized ordered arrays. In this work, 3D flower-like superhydrophilic CuO micro/nanostructures decorated by Ag nanoparticles were synthesized via an amino acid-assisted biomimetic hydrothermal method. Experiments reveal that the product demonstrates excellent sunlight self-cleaning performance in terms of wettability (without the help of high-free-energy compounds and in the absence of UV irradiation) and enhanced photocatalytic activities, which portends a bright future for this material as self-cleaning photovoltaic coatings. It is also a good example for the organic combination of green chemistry and functional materials.

Hierarchically micro/nanostructured porous metallic copper: Convenient growth and superhydrophilic and catalytic performance

This paper reports a simple one-step growth of hierarchically micro/nanostructured porous metallic copper microspheres with high yield at room temperature. The key growth strategy is to use phenol and ascorbic acid as porogen and reducing agents, respectively, to induce the growth of the porous hierarchical micro/nanostructure. The samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. It is found that the morphology and structure of the porous Cu microspheres are highly dependent on the phenol added. Compared to the commercial Cu powders and Cu sheets with dense internal structure, hierarchically micro/nanostructured porous metallic copper microspheres show excellent superhydrophilic surface property and much higher catalytic activity for the reduction of 4-nitrophenol, demonstrating the significance of the pore structure of the copper materials. Their potential applications in catalysis for oxygen reduction reaction of fuel cells are also explored. All these features make the as-prepared porous copper microspheres a highly attractive candidate for multi-functional materials.

Hierarchical plasmonic-metal/semiconductor micro/nanostructures: green synthesis and application in catalytic reduction of p-nitrophenol

Hierarchical micro/nano arrays can offer both the advantages of nano-sized building blocks and micro- or submicrometer-sized ordered arrays, therefore representing one kind of potential functional materials and having received enormous attention for a wealth of applications. In this study, four-dimensionally flower-like CuO micro/nanostructures decorated by Au nanoparticles are synthesized via an environmentally friendly route assisted by polyethylene glycol. Experiments reveal that the product demonstrates high catalytic performance for the reduction of 4-nitrophenol using NaBH4 as the reducing agent, which could be attributed to the rich Au/CuO interfaces in the samples. Compared to the pure noble metal catalysts, the obtained sample is quite economic. In terms of methodology and cost-effectiveness, this study proposes an economically useful and green method to produce a highly efficient metal-based catalyst. It is also a good example for the organic combination of green chemistry and functional materials.

Biomass-derived interconnected carbon nanoring electrochemical capacitors with high performance in both strongly acidic and alkaline electrolytes

Correction for ‘Biomass-derived interconnected carbon nanoring electrochemical capacitors with high performance in both strongly acidic and alkaline electrolytes’ by Xianjun Wei et al., J. Mater. Chem. A, 2017, 5, 181–188.

Unconventional lithography for hierarchical micro-/nanostructure arrays with well-aligned 1D crystalline nanostructures: design and creation based on the colloidal monolayer.

We have developed a strategy for designing and fabricating hierarchical micro-/nanostructured arrays based on the combination of a colloidal monolayer substrate and the pulsed laser deposition (PLD) process. In this approach, microstructures are provided by the colloidal monolayer and can be tuned by changing colloidal monolayer periodicities, while crystalline nanostructures are supplied by PLD and can be controlled by PLD experiment parameters (e.g., ambient gas pressure). In comparison with the traditional lithography techniques, the proposed method has the obvious advantage of low cost. More importantly, the complicated hierarchical micro-/nanostructure arrays obtained by the present strategy cannot easily be designed and synthesized by traditional lithography techniques. This fact suggests that the proposed method can be a quite powerful alternative to fabricate complicated hierarchical arrays by complementing the weakness of traditional lithographic routes. In addition to these, the strategy also features uniform surface morphology, room-temperature reaction, and pure sample surfaces that are highly valuable to build a new generation of microdevices or nanodevices in nanophotonics, energy storage, etc. on the basis of these special hierarchical micro-/nanostructured arrays.