Preparation And Performance Research Of Membrane Reactor For Electrocatalytic Ammonia Synthesis

Compared with the conventional Haber-Bosch process,electrocatalytic ammonia synthesis is a more environmental-friendly and energy-saving ammonia synthesis method.However,the yield and Faraday efficiency of electrocatalytic synthesis of ammonia are low,which is mainly due to the lack of electrolyte materials with high proton conductivity and cathode catalysts wi th high catalytic performance.In this work,we use sol-gel method to synthesis A-site deficient Tb-doped proton-conducting Ba_0.95Ce_0.7-xTb_xY_0.2Zr_0.1O_3-δ（BCTYZ,x=0.05,0.10,0.15）and Ba Co_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ（BCFZY）perovskite-type ceramics powder.Preparation of anode supported solid oxide fuel cell（SOFC）with BCTYZ as electrolyte and BCFZY as cathode.XRD was used to analyze the crystal structure of the powder,a thermal dilatometer was used to test the thermal expansion coefficient of each electrode material,the electrochemical workstation was used to measure the electrical conductivity of BCTYZ,the output power and electrochemical impedance spectroscopy of SOFC.The test results show that the thermal sintering curves of BCTYZ0.10 and NiO-BCTYZ0.10 are in good agreement and have good thermal compatibility,SEM shows that the electrode and the electrolyte are tightly bonded without falling off.The conductivity of BCTYZ0.10 material at 750℃is as high as 0.04818 S·cm^-1,and the ohmic impedance and polarization impedance of NiO-BCTYZ0.10|BCTYZ0.10|BCFZY single cell at 750℃are 0.237Ω·cm²and 0.008Ω·cm²,respectively,the power density is 695 m W·cm^-2,which is much higher than the power density of BCTYZ0.05 and BCTYZ0.15 single cells.The NiO-BCTYZ0.10|BCTYZ0.10|BCFZY single cell was assembled into an electrocatalytic ammonia synthesis membrane reactor,and the BCFZY in-situ reduction was used as the ammonia synthesis catalyst.The effects o f temperature,applied voltage,and cathode gas composition on the ammonia yield and Faraday efficiency were investigated.The ammonia yield is as high as 9.43×10^-9 mol·s^-1·cm^-2 at 650°C,an applied voltage of 1.6 V,and a cathode gas composition hydrogen to nitrogen ratio of 1:1.The maximum yield of ammonia synthesis in hollow fiber membrane reactor is 8.63×10^-10 mol·s^-1·cm^-2,which is one order of magnitude lower than that in plate membrane reactor.It is possible that the over sintering of cathode affects the gas diffusion and mass transfer,reduces the three-phase interface,and the uneven distribution of collector layer on anode side reduces the electrocatalytic effect.