Luhan Ye

Gas leak diffusion induced polarization in submicro/nanoscale non-tight electrolytes of solid oxide fuel cells

Solid oxide fuel cells with submicro/nanoscale electrolytes (μSOFCs) are attracting increasing attention since the ohmic energy loss arising from an ion-resistive electrolyte decreases significantly with decreasing thickness of the electrolyte interlayers. However, gas leak diffusion can be induced due to increasing microstructural flaws such as cracks and pinholes in thin electrolytes. Evaluation of the effects of gas leak diffusion through electrolyte on cell performance is thus an urgent demand. In this work, the effect of gas leak diffusion on concentration polarizations (CPs) is investigated quantitatively for both anodes and cathodes of SOFCs under various operating conditions. The results show that gas leak diffusion through electrolyte typically induces dominant cathode CP. The direct reaction of leaked H2 and O2 correlates has a large impact on both anode and cathode CP induced by gas leak diffusion. Lowering the operating temperature decreases CP induced by gas leak diffusion. Our work provides a quantitative model to evaluate the impact of gas leak diffusion in electrolytes on SOFC performance and facilitates the rational design of high performance μSOFCs.

Initial-stage oriented-attachment one-dimensional assembly of nanocrystals: fundamental insight with a collision–recrystallization model

Oriented attachment (OA) growth has been a promising method for the synthesis of one dimensional (1D) anisotropic nanocrystals (NCs). An unresolved fundamental issue is to understand the growth mechanism at the initial stage of an OA nanorod (NR) growth. In this report, a collision–recrystallization model is proposed to investigate the initial OA growth of NRs. The repulsive electrical double layer (EDL) interaction and the attractive van der Waals (vdW) interaction at the initial OA stage are derived by the accurate surface element integration (SEI) technique and the classical Hamaker equation, respectively. Our results show that the self-recrystallization of nanochains increases the collision activation energy of NPs dramatically as their surface potentials and Hamaker constants increase. Under a specific electrolyte concentration, the collision activation energy reaches the maximum, indicating that the growth rate of OA can be controlled by adjusting the electrolyte concentration.

Reduced electrochemical performances of proton exchange membrane fuel cells due to gaseous diffusion in electrolytes

In this report, we derive a ‘gas leak mold’ model to investigate gas diffusion in the electrolyte membranes of proton exchange membrane fuel cells. The electrochemical parameters of proton exchange membrane fuel cells, including limiting current density and concentration polarization are studied systematically. In particular, we investigate the correlation between fuel cell performance and diffusion-induced gas leak of proton exchange membranes. This work is expected to facilitate the development of highly-efficient proton exchange membrane fuel cells.