Surface manipulation of a triple-conducting cathode for protonic ceramic fuel cells to enhance oxygen reduction activity and CO_(2) tolerance

One of the main obstacles limiting the performance of protonic ceramic fuel cells(PCFCs) is the sluggish kinetics of the oxygen reduction reaction(ORR) at reduced temperatures.Here,the surface manipulation of a triple-conducting cathode BaCe_(0.5)Pr_(0.3)Y_(0.2)O_(3-δ)(BCPY) by an efficient catalyst coating PrNi_(0.5)Co_(0.5)O_(3-δ)(PNC) to enhance the ORR activity and CO_(2) tolerance is reported.The developed PNC-coated BCPY cathode achieves the polarization resistance of 0.25 and 1.00 Ω cm^(2) at 600 and 500 ℃,respectively,approximately 1/5 of that for the pristine BCPY cathode(0.99 and 4.79 Ω cm^(2)),while maintaining an excellent CO_(2) tolerance.The single cell on a BaZr_(0.8)Yb_(0.2)O_(3-δ) electrolyte also exhibits a high peak power density of 0.79 W cm^(-2)at 700 ℃ and a stable operation for 200 h at 600 ℃.Such high ORR activity is mainly attributed to the synergistic effect of BCPY support and PNC nanoparticles.Namely,BCPY provides a tripleconducting path(mainly protons),and PNC nanoparticles facilitates surface oxygen exchange and steam adsorption/desorption processes due to the enriched surface oxygen vacancies.This study will provide a new design strategy for developing high-performance PCFCs cathode.

Combination of multiple tools for surface manipulation of polar molecules

A scheme of surface manipulation and control of polar molecules is proposed, which combines three tools of electrostatic velocity filtering, bunching, and storing. In the scheme, a slow molecular beam is produced from an effusive beam by surface velocity filtering. Then the velocity spread of the slow molecular beam is compressed by a buncher consisting of a series of electrodes. Following that the molecular beam with a narrow velocity spread is stored in a storage ring. Using ND3 molecule as a tester, the feasibility of our scheme is analyzed theoretically and verified via numerical simulations that cover all three manipulation processes. The results show that cold molecular samples can be prepared from a thermal gas reservoir and stored in the storage ring with more than 10 round trips. Our combined scheme facilitates the production and manipulation of polar molecules, offering new opportunities for basic research and intriguing applications such as quantum information science and cold collisions.

Graphene-supported manipulation of surface plasmon polaritons in metallic nanowaveguides

We investigate the electrically controlled light propagation in the metal–dielectric–metal plasmonic waveguide with a sandwiched graphene monolayer. The theoretical and simulation results show that the propagation loss exhibits an obvious peak when the permittivity of graphene approaches an epsilon-near-zero point when adjusting the gate voltage on graphene. The analog of electromagnetically induced transparency(EIT) can be generated by introducing side-coupled stubs into the waveguide. Based on the EIT-like effect, the hybrid plasmonic waveguide with a length of only 1.5 μm can work as a modulator with an extinction ratio of ～15.8 d B, which is 2.3times larger than the case without the stubs. The active modulation of surface plasmon polariton propagation can be further improved by tuning the carrier mobility of graphene. The graphene-supported plasmonic waveguide system could find applications for the nanoscale manipulation of light and chip-integrated modulation.

Near-field manipulation of terahertz surface waves by metasurfaces [Invited]

Surface waves（SWs） are a special form of electromagnetic waves that travel along the boundary between a metal and a dielectric. The special optical properties of SWs render them very attractive in applications, such as subdiffractional lithography, novel biochemical sensors, and ultrafast integrated circuitries. Herein, we present a review of our recent progress in excitation and manipulation of terahertz SWs due to interference or coupling between a pair of slit resonators in metasurfaces, showing the ability to devise ultrathin and compact plasmonic components.

Vortex fluidic mediated one-step fabrication of polyvinyl alcohol hydrogel films with tunable surface morphologies and enhanced self-healing properties

Previous strategies for controlling the surface morphologies of polyvinyl alcohol(PVA)-based hydrogels,including freeze-drying and electrospinning,require a posttreatment process,which can affect the final textures and properties of the hydrogels.Of particular interest,it is almost impossible to control the surface morphology during the formation of PVA hydrogels using these approaches.The strategy reported in this study used the novel vortex fluidic device(VFD)technology,which for the first time provided an opportunity for one-step fabrication of PVA hydrogel films.PVA hydrogels with different surface morphologies could be readily fabricated using a VFD.By also reducing the crosslinking agent concentration,a self-healing gel with enhanced fracture stress(60%greater than that of traditionally made hydrogel)was achieved.Interestingly,the associated selfhealing property remained unchanged during the 260-s mechanical testing performed with the strain rate of 5%s-1.The VFD can effectively tune the surface morphologies of the PVA-based hydrogels and their associated properties,particularly the self-healing property.