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931.
Caizhi Zhang Hao Liu Tao Zeng Jiawei Chen Pengfeng Lin Bo Deng Fujian Liu Yifeng Zheng 《International Journal of Hydrogen Energy》2021,46(45):23489-23497
During the operation of proton exchange membrane fuel cell (PEMFC), it always suffers from reversible performance loss caused by the oxidation of platinum catalyst on its electrode, which reduces the electrochemical active surface area. Short circuit method has been found to improve the performance of fuel cells by stripping of oxides and other adsorbed species from platinum, which needs systematical understanding the effective parameters of short circuit method on fuel cell performance. In this paper, the effects of different short circuit activation parameters (duration, interval, cycles, cut-off voltage, operating current) are carefully studied and analyzed during short circuit operations. In addition, the mechanism revealing how relevant parameters influence short circuit activations is deeply analyzed. The results show that five groups of activation parameters have obvious influence on the activation of fuel cell, indicating that the short-circuit activation effect can be optimized. Among these parameters, the short-circuit duration parameter have the greatest impact on activation, because the platinum hydroxides and oxides is gradually removed during short-circuit duration and results in a larger effective surface area of the platinum catalyst for the electrochemical reaction. However, the smallest impact is short-circuit interval. Another finding is that the five activation parameters are not independent, so the optimal activation parameter value needs to be analyzed in combination with the operating conditions. Finally, according to the activation principle, selection of appropriate short circuit activation parameters for application are proposed to further improve performance and fuel utilization by considering the safety of the stack. 相似文献
932.
933.
Xin Yang Wenzhuo Deng Ming Chen Yaobing Wang Chuan-Fu Sun 《Advanced materials (Deerfield Beach, Fla.)》2020,32(45):2003592
Low-cost and high-safety aqueous Zn-ion batteries are an exceptionally compelling technology for grid-scale energy storage. However, their development has been plagued by the lack of stable cathode materials allowing fast Zn2+-ion insertion and scalable synthesis. Here, a lattice-water-rich, inorganic-open-framework (IOF) phosphovanadate cathode, which is mass-producible and delivers high capacity (228 mAh g−1) and energy density (193.8 Wh kg−1 or 513 Wh L−1), is reported. The abundant lattice waters functioning as a “charge shield” enable a low Zn2+-migration energy barrier, (0.66 eV) even close to that of Li+ within LiFePO4. This fast intrinsic ion-diffusion kinetics, together with nanostructure effect, allow the achievements of ultrafast charging (71% state of charge in 1.9 min) and an ultrahigh power density (7200 W kg−1 at 107 Wh kg−1). Equally important, the IOF exhibits a quasi-zero-strain feature (<1% lattice change upon (de)zincation), which ensures ultrahigh cycling durability (3000 cycles) and Coulombic efficiencies of 100%. The cell-level energy and power densities reach ≈90 Wh kg−1 and ≈3320 W kg−1, far surpassing commercial lead–acid, Ni–Cd, and Ni–MH batteries. Lattice-water-rich IOFs may open up new opportunities for exploring stable and fast-charging Zn-ion batteries. 相似文献
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938.
High-efficiency multipartite entanglement purification of electron-spin states with charge detection
Tao Li Bao-Cang Ren Hai-Rui Wei Ming Hua Fu-Guo Deng 《Quantum Information Processing》2013,12(2):855-876
We present a high-efficiency multipartite entanglement purification protocol (MEPP) for electron-spin systems in a Greenberger–Horne–Zeilinger state based on their spins and their charges. Our MEPP contains two parts. The first part is our normal MEPP with which the parties can obtain a high-fidelity N-electron ensemble directly, similar to the MEPP with controlled-not gates. The second one is our recycling MEPP with entanglement link from N′-electron subsystems (2 < N′ < N). It is interesting to show that the N′-electron subsystems can be obtained efficiently by measuring the electrons with potential bit-flip errors from the instances which are useless and are just discarded in all existing conventional MEPPs. Combining these two parts, our MEPP has the advantage of the efficiency higher than other MEPPs largely for electron-spin systems. 相似文献
939.
Jinyan Deng Qian Xiu Lihui Guo Lirong Zhang Gaojun Wen Chaofan Zhong 《Journal of Materials Science》2012,47(7):3383-3390
Four donor–π–acceptor type polymeric metal complexes (PCo–F, PCo–B, PNi–F, and PNi–B) with Co(II) or Ni(II) complexes in the
branched chain were synthesized by the Heck coupling and utilized as dyes for dye-sensitized solar cells (DSSCs). The structures,
photophysical, electrochemicals, and thermal properties of the four dyes were investigated in detail, and the results showed
that dye containing Ni(II) complex and alkoxy benzene unit benefited the generation of photocurrent and the open-circuit voltages.
The polymeric metal complexes possess good thermal stability and exhibit good solubility in common organic solvents such as
chloroform, THF, and toluene. The maximal power conversion efficiency of 1.21% (J
sc = 2.49 mA/cm2, V
oc = 0.695 V, FF = 0.59) was obtained with a DSSCs based on PNi–B dye under simulated air mass 1.5 G solar irradiation. 相似文献
940.