Pyrochlore　oxide　A2B2O7　is　a　potential　anode　catalyst　of　ammonia-fed　solid　oxide　fuel　cell　(SOFC)　due　to　its　unique　and　open　structure　that　can　make　some　oxygen　ions　flow　to　occupy　the　hole　position　to　form　Frankel　defect.　Herein,　various　rare-earth　ions　with　different　radius　are　selected　as　the　A　site　to　construct　defective　pyrochlore　oxide　RE2Zr1.95Ni0.05O7+δ　(REZN,　RE　=　La,　Pr,　Nd,　Sm,　Gd,　LZN/PZN/NZN/SZN/GZN)　to　gain　insights　into　oxygen　vacancies　that　can　be　the　diffusion　and　adsorption　active　site　for　ammonia.　In　the　n-type　semiconductor　REZN,　the　degree　of　crystal　ordering　decreases　with　the　decrease　of　the　radius　of　rare-earth　RE3+　ions.　Among　them,　GZN　exhibits　the　most　negative　conduction　band　and　the　smallest　band　gap,　making　it　easier　to　overcome　the　energy　potential　barrier　and　facilitate　the　movement　of　carriers.　As　a　result,　the　conductivity　of　GZN　is　about　25　times　higher　than　that　of　LZN.　The　average　TEC　value　of　GZN　is　10.40　×　10-6　K−1,　which　matches　that　of　electrolyte　YSZ　(10.50　×　10-6　K−1).　The　maximum　power　density　of　ammonia-fed　SOFC　supported　by　YSZ　electrolyte　based　on　GZN　anode　is　128.63　mW·cm−2　at　800　°C,　which　is　2.3　times　higher　than　that　of　NiO-based　SOFC.　The　single　cell　based　on　GZN　anode　can　be　run　continuously　for　100　h　at　800　°C　without　significant　degradation.　The　preliminary　results　suggest　that　GZN　oxide　is　promising　to　be　a　candidate　catalyst　for　ammonia-fed　SOFC　anode.　©　2023　Elsevier　B.V.