Performance Research Of Proton-conductive Solid Oxide Fuel Cell Using Ammonia （NH₃） As Fuel

As a new type of power generation device,solid oxide fuel cell（SOFC）has received wide attention due to its high efficiency,fuel diversity,etc.The single cell supported by Ni-based anode is the classical SOFC.However,the Ni-based anode suffers from the serious carbon deposition on the anode when hydrocarbons are used as direct fuels,what’s more,the application of hydrocarbons lead to CO₂emissions.In addition to the development of coking-resistance anode materials,the use of zero-carbon-based fuels in SOFC based on Ni-based anodes is also a feasible way to solve the problem of carbon deposition.At present,ammonia（NH₃）is recognized as a hydrogen carrier which is convenient for storage and transportation and has zero carbon emissions.Since the direct electrochemical reaction between ammonia and oxygen may generate contaminative nitrogen oxides,this work,a proton-conductive perovskite is used as electrolytes,and Ni-based ceramic materials as anodes are used.Two kinds of perovskite materials are used as cathodes to study the electrochemical performance and stability of the single cell when NH₃ is used as the direct fuel.In this case,the formation of nitrogen oxides is avoided.This work provides theoretical basis and technical support for zero-carbon fuels based SOFC for power generation.1.The anode-supported single cell was prepared with BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ（BZCYYb）as the electrolyte,NiO-BZCYYb as the anode,and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ（BSCF）perovskite as the cathode（denoted as NiO-BZCYYb|BZCYYb|BSCF）.The electrochemical performance and constant current discharge stability of the single cell were explored when 50 vol%NH₃-50 vol%Ar was used as fuel.The maximum power density of the single cell was 0.426 W·cm^-2 and the polarization impedance was 0.39Ω·cm² at 700°C.The voltage drop rate was 0.001 V·h^-1in the stability test of 95 h under a constant current at 700°C,which indicates that the cell has general stability in NH₃atmosphere,related to the sintering of Ni particles and the instability of cathode material;SEM results show that porosity reduced at the anode after a long-term constant current discharge.These results indicate that NH₃ can be used as a direct fuel of SOFC for power generation.2.Using a proton-acceptor material Sr(Co_0.8Fe_0.2)_0.7B_0.3O_3-δ[S（CF）B]as the cathode,a single cell NiO-BZCYYb|BZCYYb|S（CF）B was fabricated.The electrochemical performance and stability of the cell were studied when50 vol%NH₃-50 vol%Ar was used as fuel.The maximum power density of a single cell was 0.336 W·cm^-2 at 700°C,which was higher than that of NiO-BZCYYb|BZCYYb|SCF under the same conditions,and the polarization impedance was also reduced from 0.44Ω·cm² to 0.34Ω·cm².The constant current discharge stability test was performed on the single cell,with a voltage drop rate of 0.0006 V·h^-1 after 155 h of continuous operation at 700°C,which was better than that of NiO-BZCYYb|BZCYYb|BSCF under the same conditions.The result indicates that the doping of B greatly improves the stability of the material.SEM results showed that there was no obvious crack between S（CF）B and electrolyte after a long-time constant current discharge stability test,which indicates a good compatibility between these two materials.In summary,NH₃ as a clean energy carrier with zero carbon emissions is an excellent SOFC fuel;a cell using a proton-conductive electrolyte combined with a proton acceptor cathode has more advantages when NH₃ is used as a fuel.This work provides theoretical support for the future development of proton-conductive cathode materials.