Semipermeation Coupled to Electrical Potential Measurements

Very recently, Gelfroy et al. [56,57] have developed a technique for the direct measurement of the chemical potential gradients within a bulk perovskite film 

By combining Eqs. (14.80)-(14.82), it is possible to determine the O2 chemical potential in the bulk membrane  

Taking into account the three different potentials, buik Es,f and s.p the diffusion and surface exchange coefficients can be measured using the following expressions  

The determination of the chemical potential drop makes it possible to calculate the so-called Be parameter, which can be used for characterizing the ratedetermining step of the O2 semipermeation within perovskite membranes. This parameter is defined as follows for the feed/membrane and permeate/membrane surfaces (i.e., and Bc.p respectively) 

The lEDP method can be combined with gas-phase analysis (GPA) as alternative methods for measuring the self-diffusion and surface self-exchange coefficients. In this analysis, the sample placed in a flxed bed is first equilibrated with a controlled atmosphere kept at a well-defined 02 partial pressure. After equilibration, the feed stream is switched to 02 at the same partial pressure and the outlet gas composed by 02 and 02 leaving the reactor is monitored (i.e., breakthrough curve analysis). The self-diffusion and surface self-exchange coefficients can be measured using the Pick s second law (i.e.. Crank s equation). 

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