| In recent years,the rapid growth of global energy demand has accelerated the depletion of fossil fuels such as coal and oil,resulting in the increasing driving force to find alternative energy sources.Hydrogen,as the most important and most promising future energy with a resource-rich and environmentally friendly effect,has attracted much attention in the worldwide.High-temperature proton conductors,a series of solid electrolyte materials that can conduct protons,may play an indispensable role in many fields relating to the hydrogen industry.However,the traditional proton conductor and its related devices have many shortcomings,e.g.,high cost of the generally used precious metal platinum as the electrode?anode?materials;dis-match of the thermal expansion coefficients?TEC?of the conventional air electrode?cathode?material and the conventional high temperature proton conductive electrolyte;and the poor chemical stability of the high-conductivity electrolyte barium cerate used in the reversible solid oxide battery?RSOC?.Aiming at solving the problems mentioned above,this dissertation provides several novel methods to modify the proton conductor and its deveice,e.g.,preparing a nickel electrode by electroless plating,preparing a composite cathode by immersing the cathode material in the porous electrolyte skeleton,preparing a double-layer electrolyte by a dip-coating method.Specific research contents are as follows.1.The pure Ni electrode with a thickness of about 8?m on the surface of a high-temperature proton conductor CZI ceramic and the Ni|CZI|Ni symmetrical battery was prepared by a"two-step electroless plating"method with hydrazine hydrate as the reducing agent.The electrochemical results showed that the Ni electrode prepared by electroless plating has a hydrogen catalytic activity comparable to that of the Pt electrode at an operating temperature above 600°C.The electromotive force of the Ni|CZI|Ni symmetrical battery is almost the same as the theoretical electromotive force at the temperature higher than 300°C,and the interface between the Ni electrode and the CZI electrolyte kept well after 48-hours continuous operation.2.The dense CZI membrane on a porous NiO-CZI tube was prepared throughthe isostatic pressing,dip-coating and co-sintering process.The composite cathode of CZI-LSC was fabricated with screen-printing?preparation of the porous CZI skeleton?and impregnating methods?preparation the loading of LSC in the porous CZI skeleton?.The mass fractions of the LSC loaded in porous CZI skeleton were controlled by the repetition number of impregnation.The results showed that the RSOC with a LSC mass fraction of 50%exhibited the best electrochemical performance,achieving a hydrogen production rate of 2.1mL·min-1·cm-2 under the condition of 850oC-1.2V.Moreover,the electrochemical performance of the RSOC maintained well,though a slight decline appeared in the initial 3 hours due to the coarsening of its anode nickel particles.3.The dense BZY2-BCY2 double-layer electrolyte was prepared by dip-coating and co-sintering an additional BZY2 layer on the surface of a BCY2-NiO porous support.The effects of the additional thin BZY2 layer on the phase,morphology and electrochemical properties of the whole electrolyte were studied systematically.The results showed that the surface of the double electrolyte layer retained the BZY phase.The double-layer electrolyte showed a three-layer sandwiched structure of BZY2-B?ZC?Y-BCY2.The BZY2-BCY2 double-layer electrolyte could greatly improve the chemical stability of the RSOC without significantly reducing the electrochemical performance.In addition,the CZI ceramic with a high chemical stability was also prepared as the protective layer of BCY,but experiment results showed that the CZI would react with BCY during the sintering process,causing the decline of open circuit voltage for the RSOC and its poor electrochemical performance.As a result,it could be concluded that CZI ceramic was not a potential material of a protective layer for barium cerium. |
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