The　Ba-doped　ZrO2　materials　were　prepared　by　three　methods　and　used　as　support　for　Ru　catalysts　for　ammonia　synthesis,　i.　e.,　citric　acid　sol-gel　method　(SG),　modified　co-precipitation　(CP)　and　impregnation　method　(IP).　The　certain　amount　of　analytical-grade　Zr　(NO3)4　•　5H2O　and　Ba　(NO3)2　were　dissolved　in　deionized　water　to　form　a　transparent　mixed　nitrate　solution.　The　citric　acid　was　slowly　added　into　the　mixture　to　form　a　transparent　solution　and　then　heated　to　80°C　under　vigorous　stirring　until　all　the　water　evaporated　and　a　viscous　material　was　obtained.　After　calcination　at　750°C　for　5　h　and　a　puffy　white　powder　was　obtained.　This　was　BZ-SG.　The　solution　of　NH3　•　H2O　and　K2C2O4　•　H2O　was　added　dropwise　to　the　mixture　solution　of　Zr　(NO3)4　•　5H2O　and　Ba　(NO3)2　with　vigorous　stirring,　and　the　obtained　white　suspension　was　aged　at　60°C　for　60　min.　The　resulting　precipitate　was　centrifuged　and　washed　with　distilled　water　for　several　times,　and　then　calcined　at　750°C　for　5　h.　The　obtained　white　solid　was　named　as　BZ-CP.　The　Zr(OH)4　was　prepared　by　adding　the　KOH　into　the　Zr　(NO3)4•　5H2O　solution.　Then　the　obtained　Zr　(OH)4　was　baked　at　300°C　for　3　h　and　impregnated　with　aqueous　solution　of　Ba　(NO3)2.　After　dried　at　85°C　for　12　h,　the　sample　was　heated　at　750°C　for　5　h　and　obtained　the　BZ-IP　sample.　Ruthenium　catalysts　were　prepared　by　impregnating　the　supports　directly　with　K2RuO4　solution.　After　reduction　with　ethyl　alcohol,　then　was　dried　at　120°C　for　12　h.　The　samples　with　4　wt%　Ru　were　labeled　as　RBZ-X　(X=SG,　CP　and　IP).　The　molar　ratio　of　Ba　to　Zr　in　all　the　samples　is　1:9.　The　composites　materials　and　catalysts　were　characterized　by　X-ray　diffraction　(XRD),　temperature　programmed　reduction　of　H2　(H2-TPR),　temperature　programmed　desorption　of　CO2　(CO2-TPD),　N2　adsorptiondesorption　isotherms,　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM)　and　CO　chemisorption.　The　results　displayed　that　the　RBZ-SG　catalyst　showed　the　highest　activity　for　ammonia　synthesis　compared　to　those　of　RBZ-CP　and　RBZ-IP.　The　optimum　ammonia　concentration　over　RBZ-SG　catalyst　is　5.72%　under　the　conditions　of　3　MPa,　10000　h-1　and　425°C.　This　activity　is　3.8　and　14.3　times　of　that　of　RBZ-CP　and　RBZ-IP,　respectively.　Such　high　activity　is　mainly　resulted　from　the　presence　of　BaZrO3,　which　has　high　electron-donating　ability.　Mobile　electrons　would　be　transferred　from　BaZrO3　to　the　Ru　metal　surface　by　means　of　the　strong　metal-support　interaction　existed　between　Ru　and　reduction　BaZrO3,　which　can　facilitate　the　cleavage　of　N≡N　and　enhance　the　activity　for　ammonia　synthesis　sufficiently.　©　2013　Shanghai　Institute　of　Organic　Chemistry,　Chinese　Academy　of　Sciences.