Study On The Performance Of Proton-conducting Solid Oxide Fuel Cells Fueled By Hydrocarbon Fuels

CH₄ and CO₂ are the main greenhouse gases that cause global warming.In order to effectively utilize CH₄ and CO₂ and mitigate the harm caused by greenhouse gases,the reaction of CH₄ and C02 has attracted widespread attention of scientists.The CO₂ dry reforming of methane?CO₂-DRM?is the conversion of CH₄ and CO₂ into useful chemical products,such as synthesis gas.However,there are two main drawbacks to CO₂-DRM:the large amounts of energy consumed by the CO₂-DRM reaction and carbon deposition onto catalysts.As energy conversion devices,the heat required for an endothermic reaction in a fuel cell device can be supplied by the heat generated in the electrochemical oxidation process so as to achieve a thermogenic process.Therefore,performing in-situ CO₂-DRM on a solid oxide fuel cell?SOFC?can solve the problem that the reaction requires a lot of energy.For in situ CO₂-DRM over a SOFC anode,SOFC based on proton conducting electrolyte?H⁺-SOFC?shows outstanding advantages over SOFC based on oxygen-ionic conducting electrolyte?O₂-SOFC?because only proton?H⁺?can migrate through the proton conducting electrolyte from anode to cathode without electrochemically generated CO₂.However,a typical kind of anode materials in conventional H⁺-SOFC is Ni-based material,the main problem encountered when it used for CO₂-DRM is the anode carbon deposition,which leads to deactivation of the anode.To solve the problem of low catalytic activity and carbon deposition of the anode material of H⁺-SOFC,a catalyst layer on the conventional anode of H⁺-SOFC was designed.This method took advantage of the catalyst material in anode of SOFC and generates large amounts of electrical power and syngas.Firstly,La2NiO4 with a K2NiF4-type structure was fabricated as a catalyst precursor for efficient in situ CO₂-DRM in H⁺-SOFC?layered H⁺-SOFC?.The roles of La2NiO4 catalyst layer on the reforming activity,coking tolerance,electrocatalytic activity and operational stability of the anode were systematically studied.La2NiO4 catalyst layer exhibited greater catalytic performance than the NiO + BaZr0.4Ce0.4Y0.2O3-??BZCY4?anode during the CO₂-DRM process.An outstanding coking resistance capability was also demonstrated.The layered H⁺-SOFC consumes H2 produced in situ at anode and delivers a much higher power output than the conventional cell with NiO+BZCY4 anode.The improved coking resistance of the layered H⁺-SOFC results in a steady output voltage of-0.6 V under a constant current density of 200 mA cm-2.Therefore,the H⁺-SOFC with La2NiO4 perovskite oxide provided higher and more stable power generation by generating high concentrations of CO syngas from the greenhouse gases carbon dioxide and methane,and was a potential energy conversion device for co-generation of electricity and syngas.On the research of the catalyst precursor of H⁺-SOFC for in situ CO₂-DRM,the in situ produced H2 is consumed and high amounts of CO concentrated gas were obtained in the anode effluent.To further examine the durability of layered H⁺-SOFC working in exhaust gas with a high concentrations of CO,La2NiO4,LaNiO3 and Ni/La2O3 precursors were applied to the conventional Ni-based anode in a H⁺-SOFC for the dry reforming of methane with CO₂.The phase structures,microstructures and catalytic activities of the different precursors were systematically investigated.The cell performance and durability of layered H⁺-SOFC were examined.The layered H⁺-SOFC had higher cell performances than the conventional H⁺-SOFC.However,catalyst deactivation and degradation of the cell performance were observed as carbon deposition occurred on the catalyst layer due to CO disproportionation in exhaust gas at a high partial pressure of CO.The structure of carbon deposited on the catalysts was also investigated.