Boyun Huang

Bioinspired leaves-on-branchlet hybrid carbon nanostructure for supercapacitors

Designing electrodes in a highly ordered structure simultaneously with appropriate orientation, outstanding mechanical robustness, and high electrical conductivity to achieve excellent electrochemical performance remains a daunting challenge. Inspired by the phenomenon in nature that leaves significantly increase exposed tree surface area to absorb carbon dioxide (like ions) from the environments (like electrolyte) for photosynthesis, we report a design of micro-conduits in a bioinspired leaves-on-branchlet structure consisting of carbon nanotube arrays serving as branchlets and graphene petals as leaves for such electrodes. The hierarchical all-carbon micro-conduit electrodes with hollow channels exhibit high areal capacitance of 2.35 F cm−2 (~500 F g−1 based on active material mass), high rate capability and outstanding cyclic stability (capacitance retention of ~95% over 10,000 cycles). Furthermore, Nernst–Planck–Poisson calculations elucidate the underlying mechanism of charge transfer and storage governed by sharp graphene petal edges, and thus provides insights into their outstanding electrochemical performance.One way to improve the performance of supercapacitors is to use hybrid carbon nanomaterials. Here the authors show a bioinspired electrode design with graphene petals and carbon nanotube arrays serving as leaves and branchlets, respectively. The structure affords excellent electrochemical characteristics.

Controllable synthesis of Ni–Co–Mn multi-component metal oxides with various morphologies for high-performance flexible supercapacitors

Ni–Co–Mn multi-component metal oxides with various morphologies for high-performance supercapacitor electrodes were controllably synthesized on carbon cloth through a facile hydrothermal method followed by a subsequent annealing process. The crystalline structure, morphology and electrochemical property of the metal oxides can be manipulated by simply adjusting the Ni/Co/Mn ratio in the solution. The metal oxide prepared in the solution containing a Ni/Co/Mn ratio of 1/1/2 presents a structure consisting of nanosheets and nanoneedles, and exhibits the highest specific capacitance of 1434.2 F g−1 at a current density of 2 mA cm−2, desirable rate capability and excellent cyclic stability with a capacitance retention of 94% over 3000 cycles. To demonstrate practical application, flexible asymmetric supercapacitors based on such metal oxides were prepared and show high capacitance, low internal resistance, excellent cyclic stability and outstanding flexibility, indicating great potential as high-performance energy storage devices.

Congenerous and heterogeneous brazing of porous FeAl intermetallics

Abstract Congenerous and heterogeneous brazing of porous FeAl intermetallics has been successfully realised using Cu–10Sn green compact as brazing filler. Cu–Sn intermetallic phases combined with (Cu,Sn) solid solution were formed in the brazing line for congenerous brazing, while (Cu,Sn) solid solution was the main phase formed for heterogeneous brazing. Maximum tensile strengths for congenerous and heterogeneous brazing are 75·0 and 83·9 MPa which are about 81·5 and 91·2% of that of porous FeAl alloy (∼92·0 Mpa) respectively. The interface structure of the stainless steel and porous FeAl joint brazed at 940°C for 15 min is S–S+(Cu,Sn)/(Cu,Sn)/Cu9Al4+(Cu,Fe)+(Cu,Sn)/AlFe3+Al4Cu9+(Cu,Sn). In the porous FeAl and porous FeAl joint brazed with Cu–10Sn filler at 940°C, Cu–Sn intermetallics and (Cu,Sn) solid solution were the main phases in the joint line.

Vertically-oriented graphene nanosheet as nano-bridge for pseudocapacitive electrode with ultrahigh electrochemical stability

A hierarchical structure consisting of Ni–Co hydroxide nanosheets (NCHN) electrodeposited on vertically-oriented graphene nanosheets (GN) on carbon cloth (CC) was fabricated for high-performance pseudocapacitive electrodes. NCHN was uniformly distributed on GN, forming a sheet-on-sheet hierarchical structure. Such NCHN/GN/CC hybrid electrodes exhibit high capacitance and ultrahigh electrochemical-stability that structure and electrochemical properties of hybrid electrodes are not affected by the cyclic low-rate scanning (at 5 mV s−1 even over 1000 cycles). GN vertically grown on CC is used as nano-bridge between NCHN active materials and CC current collector, which effectively facilitates ion/charge transfer between the electrolyte and electrode, consequently leading to the ultrahigh electrochemical-stability of hybrid electrodes. To assess functional behavior, two-terminal flexible asymmetric supercapacitor devices with NCHN/GN/CC as positive electrode and GN/CC as negative electrode were assembled and electrochemically treated to demonstrate the ultrahigh electrochemical stability.

Correction to: Structural evolution of vertically oriented graphene nanosheet templating Ni–Co hydroxide as pseudocapacitive electrode

In the original article author name Qiangqiang Zhang was misspelled. It is correct here.