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Secondary Zn-air batteries (ZABs) are recognized as one of the most promising power sources for the future with lucrative features of low cost, high energy density, eco-friendliness, and high safety. However, the widespread implementation of ZABs is still hampered by the sluggish oxygen redox reactions. Thus the deployment of cost-effective and highly efficient air electrodes to substitute precious metals (Pt/Ir), is highly challenging, however, highly desired. Zeolitic imidazolate frameworks (ZIFs) are emerging functional materials, which demonstrate several outstanding characteristics, such as high specific surface area, high conductivity, self-doped N, open pore structure, versatile compositions and favourable chemical stability. Through varying the metal/organic moiety or by employing different synthesis protocols, ZIFs with different properties could be obtained. Being adaptable, desired functionalities may be further incorporated into ZIFs through pre-treatment, in situ treatment, and post treatment. Thus, ZIFs are the ideal precursors for the preparation of variety of bi-functional air electrodes for ZABs by materials tuning, morphological control, or by materials hybridization. Here, the recent advances of ZIFs-based materials are critically surveyed from the perspective of synthesis, morphology, structure and properties, and correlated with performance indicators of ZABs. Finally, the major challenges and future prospects of ZIFs associated with ZABs are discussed.

A distributed variable model for solid oxide fuel cell (SOFC), with internal fuel reforming on the anode, has been developed in Aspen HYSYS. The proposed model accounts for the complex and interactive mechanisms involved in the SOFC operation through a mathematically viable and numerically fast modeling framework. The internal fuel reforming reaction calculations have been carried out in a plug flow reactor (PFR) module integrated with a spreadsheet module to interactively calculate the electrochemical process details. By interlinking the two modules within Aspen HYSYS flowsheeting environment, the highly nonlinear SOFC distributed profiles have been readily captured using empirical correlations and without the necessity of using an external coding platform, such as MATLAB or FORTRAN. Distributed variables including temperature, current density, and concentration profiles along the cell length, have been discussed for various reforming activity rates. Moreover, parametric estimation of anode oxidation risk and carbon formation potential against fuel reformation intensity have been demonstrated that contributes to the SOFC lifetime evaluation. Incrementally progressive catalyst activity has been proposed as a technically viable approach for attaining smooth profiles within the SOFC anode. The proposed modeling platform paves the way for SOFC system flowsheeting and optimization, particularly where the study of systems with stack distributed variables is of interest.

A modular simulator of dynamic behaviour of the Solid Oxide Fuel Cell (SOFC) system, suitable for use as a training tool is presented in this article, as an alternative to expensive practical tests. This simulator, developed in Aspen Custom Modeller (ACM), captures all of the processes in an SOFC module: mass, energy, and charge balances, overpotentials, ohmic losses and electrochemical reaction kinetics. The challenges relevant to programming and mathematical skills needed for models deployment are minimised. Application of the simulator is demonstrated through i) a basic steady-state simulation and 1D optimisatin followed by estimation of the stack's distributed variables and ii) illustration of the transient behaviour of the SOFC unit. Interpretation of SOFC operation dynamics, in particular, is emphasised to show the effectiveness of the simulator for training purposes and for laboratory demonstrations. The results show the key features of the SOFC module simulator for practical applications and for virtual laboratories. It also opens up opportunities for developing an in-built SOFC simulator module in a flowsheet simulation software such as Aspen Plus and Aspen HYSYS.